The Offshore Voyaging Reference Site

Positioning of Wood Plugs For Seacocks

I’m a huge fan of the World Sailing Offshore Special Regulations, and have always used them and their predecessors as a checklist when preparing a cruising boat to go offshore.

That said, when using this resource, it’s as well to remember that these regulations were primarily written by people thinking about fully-crewed racing boats—yes, that’s changing with the rise of double and singlehanded racing, but slowly.

A good example of where we in the shorthanded cruising community need to think differently from the Special Regulations is person overboard prevention and, more specifically, getting rid of sidedeck jacklines. But I have already written extensively on that.

There is also an area where I think the Special Regulations are plain wrong:

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Jamie Still

I’ve been placing these Sta-Plug inserts near my seacocks instead of the wood plugs: easy to see and can very quick to implement. They claim “meets US Sailing Special Equipment Requirements” for what it’s worth.

Sta-Plug Mini™ (

Star Tracker

My understanding is that they will pass because they are designed and sold as a replacement for wood plugs. However I do NOT like them. When I see them present on a boat I usually advise the owner of why I dislike them, but I do not make a recommendation of it on the survey. I haven’t seen a hard answer one way or the other from DOT/TC or ABYC, but I’ll add this to a list of questions to ask next time I’m in touch with them to see if there is any official answer. I think very suitable for a race around a course(easy to install and fast) not suitable if you’ll need to rely on them for any length of time. They’re right up there with those ones you poke through and twist over then pull back for small holes.

  1. They are too soft and I would have no faith in them in any kind of an active sea.
  2. They are slippery.
  3. While they conform, there are advantages to a wood plug, bigger hole = grab bigger plug. Oddly shaped hole = bang in a spare quick to slow water, then use an Olfa knife to shape a larger plug roughly to the opening, and drive it in with a decently heavy hammer(I like a 32oz machinists hammer).
  4. Not easily secured. A wooden plug is easily secured once in place, either with wire, or a small bit of lumber or plywood. A trick for such temp fixes is to pull the hinges off a cabinet, put a hinge on each end of the stick, then you can simply push the stick into place from one bulkhead to a cabinet face or other bulkhead on top of the plug, the hinges allow for any angle. Put screws through the other side of the hinge and now something other than friction is holding it. Driving a screw down into the top of the plug secures it further.

For my own needs, I keep the plugs in a box. The odds of me having exactly what I need at hand when I find the hole is small, and keeping the plugs in the kit keeps them dry and everything in one place. This is especially useful in the oddly sized hole situation. No finding out I’ve got a wrong-sized hole and then trying to figure out what has the next size up. Each plug is labelled top and side with size, I only have 3. A project later is to colour code the sizes and mark the inside of the door or hatch with stick-on dots of corresponding colours. May never happen.
an easy and good practice method is to simply take the hose off the fitting on a thru-hull, I used to do this with owners when we were replacing the head hoses back when I was on the tools. Close ball valve, and remove hose from the barb. Open valve. No cheating and having tools laid out. I remain with the valve at all times, if they can’t do it, the valve is closed by me, I keep the hatch over where it will be draining to open, and stop the water below any electrical etc. It’s big scary the first time, but we repeat it as they find what works and doesn’t and change how they store the tools/plugs and re-test. Another easy access place is the depth transducer, although they have a flap that slows the water, and driving a plug in with hammer is not a good idea, it allows for practicing the motions of fitting the plug while water is coming in and gets the owner used to the very disconcerting feeling of the water jet and being able to see light and seawater where neither should be.
As a bonus this stress tests the bilge pumps in a way that is hard to do normally. This really drives home the lesson that pumps are good for nuisance water but a serious hull breach not so much. Most common failures are: Pumps T’d or Y’d together backfeeding when flow is high, check valves that act up, and electrical supply to the pump, as well as just plain old worn out pumps.
Kit contains:
-1 flat top machinists hammer(sometimes called a bash hammer) heavy, short and can be used to drive a plug from the face, the side or the top driving it down in tight spaces.
-assortment of plugs, enough for each fitting on the boat, sorted by size with plastic dividers, plus 2 huge ones.
-Olfa knife and spare blades
-Small prybar(often called a redbar by trades) with the edge sharpened to a knife edge.
1 half round bastard cut file, short length.
1 LED headlamp plus spare batteries
1 small LED hand torch plus spare batteries
2 6″ squares of plywood.
1 tube of Sikaflex or 3m sealant fast cure.
2 tubes kneadable epoxy putty fastest cures available.
1 2″ putty knife.
1 8″ crescent wrench
1 Picquick super 8 screwdriver(the reversible socket for the bits will do most hose clamps like a socket instead of fussing with slot driver bits).
1 pair water pump pliers(Knipex Cobras are the best).
a mix of coated deck screws. NOT stainless! The coated deck screws won’t rust in the bag, and if I need to use them in anger I want strength, longevity is less of a concern.
handful of left over small hinges.
1 handheld saw handle that can take sawzall blades, steel blade mounted, wood blade in the bag, both carbide tipped.
a few squares of left over heavy rubberized fabric, from a life raft I think.
a mix of duplex nails.

Frank O'Beirne

Agree with all this John, but prefer your option of the single wrap of tape to attach the plug to a suitable adjacent spot. The photo shows cable ties – not sure I’d want to be wrestling with cable ties which can cut the hands. Ripping away the plug from tape is a better approach IMHO. Thankfully have not had to resort to using them in anger yet!!

Steve D

Lanyard-attached plugs have ben a pet peeve of mine for decades, I simply revile them, they get in the way, I question their usefulness in that location, and they often support mold, so I’m with you.

Steve D

PS I occasionally encounter teak plugs, the folly of which cannot be over-stated, they are anything but soft.

David Shepherdson

I tried to use them to block off my engine to water heater hoses while I did some work. I could not get them to seal, I think because they are too soft and too slippery. Wood is better in my experience.

Ben Logsdon

I calculated 2656 gallons per hour, or about 44 gallons per minute coming out of a 1-1/2 inch hole at 2’ depth. Certainly worthy of being called a fire hose when you have to stick your head in a locker to (first find) then stuff a wood plug to stop your boat from sinking. Thank you for pointing out this hole (pun intended) in my safety plan! I’ll certainly be relocating my plugs to a more readily accessible location.

Tim Hynd

Good points as always John and timely for me as “emergency hull kit” is on my spring commissioning list. I’m in favor of getting the plugs out of those silly little compartments completely when possible although I’m sure it doesn’t meet the requirements. I’d much rather have it right there on a bulkhead or maybe on the inside of the door panel mounted with wire ties single screw wire tie bases.
Slightly off topic question, what did you end up doing above the new black pvc sink drain T? My galley sink is very close to waterline depth and clamping heavy duty wire wound hose onto house grade sink fittings doesn’t feel great. I’ve never seen a way to make that a solid connection without using those flimsy “slip joint” fittings…

Dick Stevenson

Hi John,
I came to the same conclusions by a bit of a separate route. Initially I noticed mold and how damp the bungs were in the bilge tied on as they were. Decades ago, it was my understanding that one drove the bungs where they needed to go and that they expanded as they soaked up moisture to stay in place. This led to my having a bag of bungs easily accessible in a central location not in the bilge. (My seacocks, barring one, are all within a couple steps of each other making this easy.) In this way, the bungs were always dry. I remain curious about whether swelling really plays any part in the usefulness of bungs, but I do remember reading this 40-50 years ago.
It was later, when I started writing about preparing a boat for a flooding event, that I realized how compromising water would be to access a bung tied to the seacock and, especially, to finding the leak if the water has accumulated to any extent.
My best, Dick Stevenson, s/v Alchemy
There is one hole that a bung likely will not work to close: the shaft log. One of our boats was bought salvage after sinking and we missed that the shaft must have been subtly fractured. On a calm lovely morning a few weeks after launching after re-furbishing the boat, we lost forward momentum. I put it in reverse: initial response going backwards and then nothing. A few seconds later we heard the bilge pump go on. I had backed the fractured shaft out of the shaft log and water was gushing in and no bung would fit the narrow space. Luckily, we were at a stage in our lives where diapers were always close-at-hand. The diaper stopped the leak marvelously.

Gregory Silver

I am interested in the StaPlug or similar soft plug as they can be hand-pressed into place according to the mfg’s directions. I understand a soft wood plug needs to be driven by a mallet and so unless you had a mallet stored with each bung, that impedes response time. John, slightly off topic but I see you replaced your waste outlet hose with ‘wet exhaust’ type. Is this a good solution throughout the waste plumbing? I am fixing up a boat in Florida that has this wet exhaust hose throughout and we do have some odour issues, wondering if that hose us the culprit.

Dick Stevenson

Hi John and all,
Sanitation hose was mentioned and I have some suggestions that others have been happy with that are a bit unconventional, so I thought I would share even though off topic. Read no further unless interested in some “more than one wants to hear” thoughts on sanitation hose and smells on a boat.
I wrote this a few years ago for another venue:
A sanitation hose/marine toilet/head suggestion:
There are lots of methods for avoiding the sanitation hose blockage/toilet problems: some are common sense: pump a lot; while others take varying methods of effort (soaking in vinegar) or courage/nerve (muriatic acid) and effectiveness. All have adherents, but none seems to have risen to the level of “solution” or “best practices”.
With the idea that fooling with the sanitation hose every now and again is inevitable for any cruising boat, picking one’s time and making it very easy made sense: we developed the following and have executed this to good effect a few times already. Feedback from others who have followed these suggestions were positive as well. (We are now in a cruising area where a composting toilet makes sense.)
A few initial notes:
1.    A powerful heat gun (a hair drier will help in a pinch) is a huge help at dealing with any removal or installation of hose (any plumbing hose actually not just sanitation hose -wire reinforced is tough though no matter what you do). Heat also contributes to the hose “setting” around the barb when tightening hose clamps.
2.    When initiating repair, lightweight disposable aluminum “meatloaf” pans in various shapes are a huge mess mitigator. Find ways to shape them under connections (and design connections with space below for the pans) to catch the always yucky (technical term) water/sludge that is bound to emerge. Be patient with the drips: premature breaking the connection can, often does, lead to a bit of an uncontrolled flood. Cleaning the pans is made easy with a hand pump vacuum container such as many of us use to change our oil.
3.    A little swipe of dishwashing detergent goes a long way to helping get hoses onto barbed connections and quickly washes away.
I have switched my thinking over the past 10+ years. After decades of buying the highest quality sanitation hose: the kind that is basically built like multi-ply steel-belted radial tires with wire spiral reinforcement, I have gone to what I think of as the “cheap stuff”: solid white “rubber-like” hose with no wire reinforcement. The difference in price is impressive and the flexibility/ease of handling is equally astounding: much much easier. We have found that there have been no smell differences between the two types, a big selling point in the advertising of the expensive hose. (This may be because we do extra pumps to clear the line.)
What we do is swap the hose for new on schedule before there is a problem. (We re-build the toilet at the same time and just replace the joker valve and other similar replace-able items even if looking good.) Doing the job on schedule allows us to do the job in the most convenient position: usually on the hard with access to other sanitation facilities for our needs, fresh water, and power for the heat gun and no urgency (in contrast to the times we have cleared a blockage and/or swapped hoses at anchor). Measuring and recording each hose run carefully the first time allows you to cut new sections ahead of time, again easing further installations.
Removal is a doddle (in large part because it is not wire re-enforced nor is it multi-ply and very stiff). Flush with lots of fresh water before proceeding. At the low connection points, use disposable aluminum baking pans and mold them to catch drips/puddles (like under the joker valve): duct tape can be used to direct and secure the pan/drips and be patient. Without the wire spiral, easily cut chunks out of the hose anywhere, remove hose clamps, heat at the connections and pull free. If there is a vented loop, ensure it is not clogged (often the case in salt water): especially the “vent” part of the vented loop. 
Installation is easy and quick. Not being wire reinforced nor being multi-ply, cutting is easy with simple sheers or a stiff sharp knife: hack saw works well also. Use a heat gun to heat the whole run and wiggling the hose most anywhere is a doddle as it acts (a bit) like a noodle. This hose is not wire reinforced so avoid sharp turns: finding routing with wide curves is usually not a problem (our old wire reinforced hose did not bend sharply so the previous route was fine). When warm, one can get the hose between 2 fixed points without too much wrestling, unlike the wire re-enforced hose, and allows installation without removal of diverter valves, vented loops etc. As the hose cools, it takes on a set and stiffens up considerably.
The next go-around of replacement, you have exact measurements which makes the installation go quickly. I thought I would need to redo in 2-3 years of full time live aboard, but I was surprised that at 4 years, I did not need to replace every hose section (I still recommend 2-3 years, as replacement is so easy: it quickly becomes clear where build-up occurs and you can fine-tune your efforts). There was no smell or problem. It may help to have been live aboard and have a lot of action through the hoses rather that their sitting for periods with salt water and deposits in them. We also make a habit of pumping thoroughly. The last 3-4 years of 6-months-on/6-months-off the boat has not seen any smell permeating also. Interestingly, I have found roughly the same amount of build-up diminishing the hose’s ID as when living aboard.
At the same time, work the seacocks thru-hulls, clean them of build-up and lubricate
Not dealing with wire reinforced hose is a huge pleasure! And saves money on band-aids.
Come back with questions/comments.
My best, Dick Stevenson, s/v Alchemy
Ps. When it comes to conventional head set-ups, one of the key ingredients to not having odors in the head is that I have insisted all along that all gentlemen sit for all deposits: liquid or solid (this is a given with composting heads). Men usually consider their aim as far better than it actually is. And then there is the splatter effect. If resistance is encountered, suggest he clean the toilet and toilet area for the future.

Star Tracker

Re: questionable strength PVC etc. A temporary fix is a strip of copper all round, 2 wraps around the hose near the fitting and the ends screwed with a #8 pan head to a close bulkhead. Even if the fitting on the sink fails, the hose cant easily fall to where it can siphon.

re: wood plugs. A good smack with your hand will set it well enough to buy time to go find said hammer and seat it properly, I like to see relatively even shavings around the edge of the hole, often you’ll see it bite one side first, but when you have shavings all the way around the sound changes a bit and it feels solid. Practice makes perfect. A few plugs and a random off cut of pipe from the yard makes a great test to get comfortable before in water practice.
This is the thought process I usually stick to when deciding to fit a plug.

1. I need to plug this for 20 minutes to re-evaluate but won’t be leaving the area, boat is not moving(wack it in by hand, this is always step 1).
2. I need to leave a slip and am heading for a nearby lift in calm weather with at least one other person on board(wack it in farther with hammer until shavings are even).
3. I need to leave the vessel unattended for any reason, or I am alone and need to move it, or have more than a couple hours run to the lift. (wack it in with a hammer, install cross bar or wire it down tight, a simple screw in the top of the plug through a bit of all round or wrapped with wire works well). Only in this last case is the swelling really noticeable when you remove it, but I am in a high humidity climate, might be different where it’s warm and dry.

I prefer to have a dedicated kit everything in it’s place in the bag. Water coming in, direct another person grab kit from labelled door they were shown prior to departure while I find the problem. Easier than “go find me the hammer, it’s in the yellow dry bag under the aft bunk, oh it’s not in the toolbag? My headlight has no batteries, where is yours? Now I need a file to sort out the hole a bit, no that’s a metal file” And so on. Does it meet the requirements of adjacent? Not at all. For my use on my personal boat only, I like it best.

No smell hoses are great. A good budget buy to be aware of is that both Greenline and Newline sell marine hoses, proper certified ones, for everything from fuel to waste. A particular favourite is the wire-reinforced ultra-flexible hose. All the benefits of a wire wrap, none of the headaches for fitting, I’ve often eliminated enough elbows to fill a box, and the end result has only 4 clamped connections, especially useful with wet exhaust but not cheap. As a bonus they carry them in long lengths, as well as a huge array of fittings, many chandleries have figured this out and charge you the same as retail hoses, they often order their fittings from them or from a company called Fairview fittings too, then mark up nicely! Instead by buying direct you get them often at 1/2 or less, have a chat with people who know their products very well, and they stock all sorts of neat bits and bobs. Many times a past customer wanting to DIY has phoned me from various chandleries about town before going there and they build a better solution right on the counter while you watch! A good habit to suggest to new boat owners get in is simply flushing the hoses with fresh clean water from the dock(not the tanks) and close the seacocks if they’re going to be away from the boat for more than a day or two, and the fresh water+wipe around the head helps too. It will still have a bit of fresh chlorine and less growth(usually) than tank water. If it’s used often, simply flushing the lines for 10-20 pumps depending on the length of the run every time you’re about to leave, this also sticks in their mind to check the toilet is in the safe position. Even the best hoses have a hard time when left full for long periods. I experimented once early on(and only once!) with letting cleanish sea water stand in a sealed container for a week then giving it a sniff to see how much effect the flush water type has when left in the system for a while.

Charles Robinson

I do something a bit different. I have a dedicated “leakstop” bag. It contains wooden bungs, rubber ones (large for engine inlets), self welding tape, duct tape and a rubber hammer. It is all very well to have the bung but if you cant get it to stay in then it is useless. So in one small grab bag, I have all the kit. OK so I may lose 10-15 secs getting it, but I have all the gear with me.

Arne Mogstad

Being totally unaware of any regulations around this topic when I bought my first boat last summer, I was told by the surveyor that I should do as “everyone” does, and store the correct one next to each through hull. The more I thought about this, the less happy I was with the solution. I ended up with a simular strategy as you, with a “compromised-hull-grab-bag”. It contains pretty much the same (plus fat/vaseline/grease, as I sincerely believe that a blob of fatty goo under a plate attached to the hull can seal quite a substantial leak), and it’s stored centrally and easily accessible.

I consider this just as important as my grab bag, as most statistics tend to favour keeping water outside the boat to increase chances of survival. Off topic, but a good fire fighting strategy hopefully removes all need to ever use my life raft…

But I really like the tape trick! Fixed in place is good. Predictable! Though I might use masking tape instead (more predictable to rip, and work fairly well wet). I will however keep my bag until something better comes along.

Kevin Dreese

That’s what I had as well. All in a single bag and always in the same place along with a rubber mallet. My boat was only 25 feet so it was pretty easy to get to everything quickly but never had to use it.

I always thought it was strange to attach the plug to the thing that would break and need to be plugged… the image of me sticking my head over the gushing water trying to find the plug led to the bag idea. Also, a lot of the lanyards tying the plugs seemed too short if you ever needed to get the plug in the hole. LOL

Marc Dacey

I actually had this problem in reverse: my galley drain pipe nipple made of mild steel fractured at the threads of my bronze seacock and nearly sank the boat. I stopped or at least significantly slowed the leak with self-amalgamating tape (which has, over the years, become one of my “secret weapons”). A diver pal rammed one of the Forespar spongy cones up the pipe nipple from beneath the boat, and I was able to remove the seacock at dock, block it over better, and get the boat hauled to have the nipple replaced. All of my nipples are now stainless and every seacock is Marelon or TruDesign and I sleep easier.

But I still have a box of softwood plugs and a wee rubber mallet.

Marc Dacey

We have the same in a small, red, metal toolbox. I’ve thrown in a couple of AWAB clamps and a spare quarter-inch socket wrench with the usual 7 mm socket.

Bernard Vey

I wonder if a plug built like a mini-umbrella in SS would work fine. It could have a 12″ stem to insert in the broken hose or hole. Once outside the hull, the water pressure would open the umbrella and plug the hole. It would fit to almost any size hose or hole. Something comparable to the fixations we use to hold heavy things in a gypse wall. Would it make sense ?

Simon Robinson
Bruce Senay

No better ideas but what else can go wrong you ask. (Wire ties AND tied wooden plugs near thru-hulls seems like the way to go.) When I bought my Island Packet 45 back in 1996 I tied plugs to each thru-hull. Sometime in the ensuing 17 years, including a circumnavigation, one plug became wedged between the aluminum diesel tank & the thru-hull leading to a fuel leak from 3 pinholes from acetic acid leaching from the wood and eroding the tank. Five thousand plus USD later for repair learned to keep all plugs securely stowed but near my thru-hulls.
I don’t remember you writing on wood types, curing methods, aging, and acetic acid leaching effects on metals before. Might be something useful to your readers if you haven’t.

William Balme

I’m curious if anyone has actually used a wood (or other) plug in one of these situations? Seems to me that unless the whole thru-hull or pipe comes off leaving a gaping circular hole, they are a complete waste of time! You can’t stick a bung in a jagged broken pipe and hope to seal it. Moreover, regarding Dick’s comment, if a soft wood plug is going to do any good at all then yes, it has to start off dry so that it can expand – and yes Dick, I think it would. One stored in a damp place will have already absorbed all the moisture it wants and therefore becomes simply a wedge – so you could use any material you want to fill the hole!
And as John has pointed out, good luck with that with 44 gallons/min coming at you!
Are there many documented instances of thru-hull failure – and are all instances related to some gorilla attempting to rotate a seized thru-hull? In which case, in all likelihood, the resulting hole is unlikely to suit a round sectioned plug…

(I think…)

Dick Stevenson

Hi Bill,
I know of a lot of leaks that have occurred on boats, but I have not heard of a catastrophic failure such as what is being discussed (except for my own which I just described): although I am sure they occur. (And, for good reason, catastrophic leaks may never be reported.)
My sense is, back in the day, seacocks (construction and installation) were put in without much in the way of regulation/standards. They were vulnerable to someone stepping on them and snapping them off for ex. which would leave a nice hole, probably perfect for a bung to close.
Also, my sense is that, for a round hole such as bungs are designed for, with the taper (and some adrenalin) one could get it into the hole slowing the water and pound it home with a mallet or winch handle. That said, I agree, most leaks, even those that are catastrophic and end up sinking the boat, do not lend themselves to remedy by bung.
A cracked hose, leaking stuffing box for the rudder, a back siphoning toilet: those leaks need to be found and found quickly before rising water hides them. That is where the early warning of a high water alarm might make all the difference rather than learning when your ankle gets wet.
My best, Dick Stevenson, s/v Alchemy

Alastair Currie

Yes there are documented and investigated seacock failures that have resulted in sinking, where the UK Marine Coastguard Agency have investigated. Usually in the fishing boat fleet. Also actual failures discussed on UK Sailing forum.

Search on seacock, only the Random Harvester is a failed seacock, the rest are issues with seacocks. see

Yachting and Boating World forum discussion topic on actual seacock failures (should be able to view as guest). Useful anecdotal and factual comments:-

Cox Engineering is a sailing orientated site of engineering information for sailors. The bloke is an ex metallurgist so the focus is on metallurgy and corrosion. See pictures of failed seacocks:-

It definitely happens, but rarely catastrophically and for offshore sailing a well found vessel, maintained correctly, it should be a very, very low probability of happening.

Alastair Currie
Star Tracker

Groco, Buck Algonquin are all good. The biggest thing in any install is to fit the proper flanged adaptor(and not the one where the ball valve and plate are one), many shops who bloody well should know better are still sticking ball valves on thru-hulls. I remember 14 years ago or so annoying a wholesaler to order the adaptors for me, they had ordered them before and nobody ever bought them! This was the biggest wholesaler on the west coast at the time.
I like a nice solid glass backing plate under that, I laid up a sheet many years ago by simply tapering in my edges so it had a bit of a curve on one side, the other side was flat on a waxed table. That sheet lasted me 10 years in the trade! Personal preference on my own boat when it was glass: I don’t through bolted the flanged adaptor, nor do I like studs. 5/16″ stainless steel lag bolts just thick enough that the tip will pass through the backing plate stock.
Big source of issues is that many chandleries have the valves in bronze but the next stage fittings are “marelon”(usually just nylon) or brass. Bronze ones are expensive and worth it, seen many more failures here than the valve itself.

Plugs will work in a hose, but not very well, however knife, saw or hammer that hose can move. They are wonderful with sewage filled hose though, hold hose in one hand, wack plug in. Figure out how to solve the issue, or plug the other end and pull the whole mess out still full, if pulling it I wrap it with tape. My favorite is the tape for the shrink wrap plastic, tears easily, sticks well.

Wilson Fitt

I had a bad experience with Buck Algonquin seacocks. They started to freeze up within a year or so of being put into service so I eventually replaced all of them with Groco seacocks which have now provided nearly 20 years of faultless service with very minimal maintenance.


Star Tracker

Yep. Only 4 times in oh @#$ type scenarios, all except the first time on other people’s boats, where having it all in one place when they’re running down the dock in a flap helps. Doesn’t much matter if the pipe is jagged, if the inside portion is hanging on and in the way, a good smack with the hammer(or the hand held sawzall blade holder with carbide teeth) gets it out of the way. As a general rule, if it’s still leaking you need to hit it again. The softness isn’t so much about the swelling it’s that the plug will conform when hit into a variety of openings. Weird uneven hole? bang in next size down, use the knife to adjust the plug, an olfa knife can make a proper soft wood plug oval, triangular or square in 10-15 seconds, or if it’s easier the half round file to clean up the hole.
The swelling is only relevant in my experience for long term plugs, but I’m in a humid climate so others experience may differ, however they all seem to swell a bit after a few hours submerged. The soft wood part is always relevant.
Many many times in practice to get owners comfortable with the procedure. Usually in an actual failure t’s clever owner tricks where they’ve added on Ts and all sorts of fittings until they’ve got a nice foot long lever on the thru hull, then somebody steps on it. Crunch. Not an issue if the thru hulls are installed to code, but few are.
They are also handy with a break farther back in the system, like a broken plastic or brass nipple but the seacock is seized, this is much more common of an issue. I find if you stop to talk to the owner and figure out the whys and hows it’s usually not helpful when they are too panicked. Get permission, and a where if they have any idea, find failure, plug. Then it’s time to figure out the details.

As a bonus, with plugs you can change a seacock in the water, go outside, push it in. They’re also VERY handy when dealing with a plugged head and a hose you might not be able to get containment on, deck fills that have lost a cap, etc.

Todd Smith

Hi John, I really like these types of conversations. It is too easy to set and forget these types of measures and since no one I know has ever done this out of necessity it seems like a great topic to raise! I like the idea of the zip ties and locating the plug well above the through hull. The conventional photos you see of the plug tied to the seacock handle invite the plug to become saturated and skanky before you use it. And yes and one time mine were all wet, and a little skanky.

BUT HERE IS ANOTHER TAKE on the entire issue: Honestly, on a well maintained boat with maintained seacocks and hoses and clamps how big of a risk is this? Am I missing all the anecdotal stories? Does this really happen or is this like prepping for an asteroid hit? Also, what happens if you cannot get the plug inserted and seated and stay in place? What then? First, since I am Captain Obvious, I would just reach down and close the seacock, all of which would be tested before a passage. A bigger threat in my mind would be hitting a hard object (or failure from motion stress) and sustaining a small crack in the hull that allows water in. Plugs wont help there. I keep (many) toilet bowl waxes handy in the crash kit and thin sheets of various sizes of starboard and delrin cutting boards. (I don’t remember, maybe I learned that here from you John) That way I can sandwich the wax over a crack and wedge or screw it into place and it even allows for a little flexing.

Also, riddle me this: Has anyone tried this plug procedure in practice? I have, and wow, cue the comedy reel! I have tried placing the softwood plugs in an open hose well below the water line with the seacock actually open, full on geyser style, just to put some adrenalin in the mix. I wish I had thought to take a video. It was nuts! the water, the swearing, the feeling of total klutzness! Of course I was still in a calm harbor and not tossing around in a seaway, at night, in a gale, sleep deprived, which I imagine is about the only time MR. Murphy would make this actually happen, at least to me. And, I found it is REALLY difficult to wedge the plugs into place so they stay. Esp in the end of a soft hose. Try this from the safety of your own home with a spare piece of rubber water or bilge hose and a plug. Push it in as hard as you like. Then put the other end in your mouth and blow, pop! It might stick better in sanitation hose if you can push hard enough and it is not coated with sewerage or scale. Realistically, it may require cutting the hose remnant away from the thru hull to get to solid material at the seacock. Tick-tock… Even then, you may not have the space to hammer it in and even if you do with all the water and adrenalin flying around and the motion of the boat, not an easy task. More tick-tock… If the plug is already wet from the bilge area and maybe covered in slippery bilge concoctions, forget it. Even if successful in placement, how do you keep the plug in place where the valsalva-like action of a pounding sea wouldn’t send it flying across compartment? I know the soft wood is supposed to swell and hold itself there. How long does that take? Still more tick-tock… Anyone been lucky with that or want to trust their survival to it? Maybe I am just not catching on and this is easier for others than for me. What I do know is the wax is a LOT easier for me to place and to keep stuffing more and more in while I recover my confidence and composure and I can then easily wrap a plastic bag or fabric over it and zip tie or clamp into place. I could also experiment with other putties available that might have even more density and grip. I have not yet tried that. Also, anyone keep expansion foam on hand? That stuff sticks and bonds to absolutely anything. I think I still have some stuck to me from 1997. I like and do keep some of the forespar plugs in the crash kit, but I doubt they would work well on smaller openings (just a hunch). That is for another test…

Markku Mäki-Hokkonen

Great artice and discussion overall!
Yachting Monthly had crash test boat series about 10 years ago including through hull failure and handling a holed boat situation. Here is a link to the video showing different fixes to through hull failure situations.
Key takeaway from those videos to me is that leaks are substantial and create stress and panic. Access to the failure point can be difficult. Still there is a lot of time to act. Almost anything, like using a potato works suprisingly well and buys time to manage the situation better.
Personally I have a dedicated leakstop bag like Charles. Never used it though.

Eric Klem

My initial reaction to reading this piece was similar to Todd’s in that I focused on the issue which is the seacock and not the sometimes solution of a plug. It sounds like John does know of an account where the plug helped but I haven’t seen it mentioned if the seacock was really up to the job in the first place. I personally find it ridiculous that builders can put in the crummy 5 year brass thru hulls and valves and then we are required by surveyors to carry plugs. We carry one of the forespar plugs and then 3 different sizes of softwood plugs corresponding to the thru hull sizes but they all live in our emergency locker which is very easily accessed and well organized. I have done battle a bit with surveyors on this but once they see that we have proper seacocks in good shape, no one has forced us to move the plugs to by the seacocks yet. I hadn’t thought about how hard it could be to find the plug with water gushing in, that would really add to it. If I get forced to, I will follow John’s lead with the zip ties, I like that. I have once had the experience of a hose splitting and used the seacock and I have had a few more issues like having a stuffing box come apart and delivering a boat whose bilge pump siphoned on one tack but I have never personally seen a seacock failure.  I do know of 2 seacock failures (well one was technically a thru hull fitting with a ball valve) that happened with people aboard and in both cases it was not a full failure just a decent leak so a plug would not have done anything unless you cut/broke it all the way off which they didn’t want to do for fear of causing bigger issues. Also, in both cases there was significant user error which was the root cause.

It can be hard to see the big picture on these sorts of things and it seems to me like good seacocks get you into a pretty good place big-picture wise but I certainly have not properly looked for the data on it. If it becomes obvious plugs really measurably change the safety profile, at least John has documented a quick and good way to do it so I can easily implement that.


Ben Logsdon

Interesting thought about the wax. I kept a small ball of butyl sealant handy to plug small holes in an aging plastic canoe when paddling rocky rivers and dragging bottom a lot…a baseball sized wad of that stuff might seal off a bigger hole…

Alastair Currie

A lot of stuff around seacocks is based on historical failures, which I wonder if they are still relevant. There was time when iron cocks on wooden hulls with natural rubber hoses provided significantly less reliability than today. Then again, in the EU, the Recreational craft directive, only requires a life cycle of 5 years for seacocks which resulted in many failing due to dezincification. This has been somewhat offset through knowledge, but there are still instances of seacock failure today. Often reported in forums during winter repairs when trying to free a seized ball valve handle or change a heads hose.

The water flow rate is high, but the pressure is low, hence stopping the flow is very easy, by just placing your hand over the opening. This is something I have done with logs on many boats, set deeper than 2’. The pressure at 2’ is only 15.5psi, and not much more if moving.

I agree that a team that knows their boat, understands where the seacocks are, the size and location of softwood bungs, would be better served by stowing the plugs some where else, other than in the space where the seacock is. I keep mine in a drawer, plastic box and have a map of the locations of things (developed when the boat was new to me) and know what size I need where. If I have a failure, almost negligible probability in my view, I can rapidly retrieve and fit the bung. Be wary of ramming softwood bungs or any type in with a mallet, in case the force splits the remaining material. Soft wood should swell somewhat once fitted and strong pressure from body weight or muscles should be sufficient.

On charter fleets and racing boats where crew members are not consistent and may have less detailed knowledge of the boat than is desirable, having the bung near the fitting is a good idea. I am a fan of lanyards in this case, as water has a tendency to displace stuff as it sloshes around, so on charter boats, or where crews are new to boat they have a better chance of finding the seacock wooden bung if required.

For UK commercial coding the the wooden bung location was certainly the same description in the past, adjacent to the seacock, but recently I was involved in coding and that was not on the check list anymore, just a comment around a suitable means of closing.

Commonly used check lists for UK coding requirements, where hull openings are mentioned:-

Star Tracker

I’m not sure if it was a stock design or not, but Island Packets seem to have stuck plastic nipples in every fitting. Unsure why, sample size is only 2 so far, but they weren’t serviced in the same yard, and none had a log of the installation. One of them turned out to have been getting told to sort it for two previous surveys in a row!

When in doubt you will find a way to sort it, if it means the seacock needs a couple of wacks to finish the job and get you a pluggable hole then that’s life. The plug doesn’t even need to be well fit at first, just getting it in, and even light hand pressure will drop the water flow to nothing. Actually when we practice one of the first things I get the person to do is to hold the plug, and count to 60(for owners who don’t like to listen, the reason given is to allow the wood to swell a bit). This gets breathing back under control usually, and brings thinking back into the picture. How to make it stay there is much easier when you are calm.

Spray foam is unfortunately in my experience pretty useless. I have only tested the single stage in an aeresol can ones, perhaps the 2 part in the propane tank style FrothPaks may do better. Where it is useful is as a secondary stage, either to slow water a bit(but a toilet bowl wax ring is far, far better for this) around a fitting or patch that isn’t quite 100%. The one time I can think of where it was useful was on a powerboat, blew a chunk out of it’s exhaust system below waterline, pumps failed and then the other engine quit, all in under a minute, heading down a steep sided river. The owner had ignored the specific request to stick to the lake or at worst to go UP a river and thus drift down in a pinch for the first sea trial of a floating pile of poop that was once an ugly bayliner he got for 500$. No access was possible to the hole, clearance between exhaust and transom was smaller than a finger. Folded over bit of cardboard stuffed in the underside to stop it falling through, filled with spray foam. Fixed other motor, and one pump, motored home and fired the customer.

Christopher Barnes

We have plugs (wooden & then a few of the funny foam ones extra) nearby thru-hulls and seacocks… although given this input we will evolve the stowage system and bit.

We do have reflective dots visible and on, or obviously adjacent, to the locker or floorboard to access all the thru-hulls (2) and seacocks – it is part of our pre-passage “briefing” to remind all aboard that if they see water to start the hunt by exposing all the thru-hulls and seacocks to look for problems.

I’d also agree (strongly) that good maintenance and testing of seacocks & the associated connections go a long way to mitigating this risk. With an aluminum boat with standpipes and seacocks above the normal waterline, we are far more concerned about the engine shaft seal & a hard object direct hit to the forefoot and speed/depth sensor thru-hulls.

Curt Dawson

Seabung is a brand of externally expanding plugs like those mentioned by Bernard. I found them for sale at Landfall Navigation in the U.S.

Pedro Fernando

never used it, but Stay Afloat might be a good “first aid stop the bleeding” option, buying time for a more definitive fix en route to the nearest port.

Viv Wright

Thanks for the reminder. Such a simple piece of wood that is so important!

Part of deck officer training in the Navy involved fire and hull breach courses. The course is run in a specialized land based hull section that mimics below the waterline breaches. The force of water through multiple breaches is incredible! We were up to our necks in minutes, diving down to try to locate the ‘holes’ to drive wood wedges with mallets to stop the water.

Yes wooden plugs that are quickly accessible and usable along with powerful manual and electric bilge pumps are essential.

Star Tracker

Wasn’t sure where to put this comment. I was thinking of this thread while floating a mid 40’s boat that sank. It was already sunk and I needed a quick plug(opened the seacocks etc to stop from blowing out windows as she floated up) as I did not wish to dive inside again in a confined space with lots of hazards where a rollover was theoretically possible as she lifted. So I tested wood and the foam plugs for closing the open drains once the water level was below the windows and the trash pumps could be engaged. Let me know if there is any interest in what worked and didn’t. Foam plugs were handy for a quick minute but tended to bugger off at the worst time. Under tow the wood plugs stayed happily in place, the foam plugs all left, and that was at <2 knts.
3 things that worked incredibly, incredibly well(better than petit splash zone epoxy) were surprising to me. All are being added to my boat kit. The single best was a product called Hydraulic cement, I put it in freezer bags, added a handful of seawater, mixed, got in place, tore a corner and squeezed it into the holes. 6 minutes later the holes were sealed hard and solid. These even survived the yard’s disaster(hydraulic failure) which destroyed the boat. The other surprisingly most useful patching agent was an old string mop head and a can of roofing tar. That held for over 6 hours under tow in a reasonably active seastate in holes I could not patch safely any other way, stuffed through from the inside.
We had a combined lift capacity of 4000KG of lift(about 10k lbs) purchased for 1315$. Not feasible to carry with a vessel, but fairly easy to source worldwide. The CG officer monitoring was quite amused by the choice and asked for photos.

Charles Starke MD

This is such a good and helpful comment! Thank you. Please add any other information you have!
Best wishes,
Charles L Starke MD FACP
s/v Dawnpiper

Dick Stevenson

Hi Viv,
Yes, a training that simulates a flooding event can be quite sobering and can emphasize preparedness.
I would suggest, for most of us with shorthanded crews, often of two: husband and wife, that manual pumps not be part of a response equation until the leak is found and stopped, and de-watering is the task.
As you noted, finding the leak (and stemming the leak) becomes increasingly difficult with rising water, so the very first order of business with a leak is finding the leak. And with a short-handed boat, all hands should be looking: having prepared a plan and practiced ahead of time .
I will further note that a leak leading to a flooding situation is very unlikely to be much affected by a manual pump: and that would be for only a short period as the pumps that move considerable water are a fair amount of work and exhaustion, even with adrenalin running strong, will quickly ensue. Electric pumps might buy time to find the leak and do not take a crew away from searching.
More on my thoughts on preparing a boat and dealing with a flooding event can be found at
My best, Dick Stevenson, s/v Alchemy

Yanick Levasseur

I have a Turkish acquaintance who, one day, had the sink valve in his boat break flush with the hull, creating a very big hole. Not having any wood plugs at his disposal (what Turk does?), he took an eggplant and pushed it into the hole. He sailed for 15 days and worries, without using his sink.

Chuck Batson

A table of water ingress rates for various hole sizes and depths can be found at It is sobering to consider how few of the entries can be managed by the high-capacity pumps available for yachts, especially after factoring in voltage drop, vertical head, etc.