A Tale Of Two Water Heaters

Last year our venerable and functional 9 gallon Allcraft water heater (on the right) finally bit the big one after 15 years of faithful service. And, wouldn’t you know it, Allcraft had gone out of business.

So, after some fairly perfunctory research—how big a deal could a water heater be?—we ordered a new stainless steel 10.5 gallon water heater from Atwood Mobile Products (now Dometic). Sadly it has turned out to be a disappointment and near useless to us for the following reasons:

  1. The thermostat can not be adjusted and is set way too cool. (We have an automatic temperature constant mixing faucet in the shower, so there is no danger of anyone getting burned if we set the thermostat a bit higher.)
  2. The minute that you use any of the hot water and it is replaced by cold water, the remaining water in the tank becomes barely warm. We think this is due to the heater’s squat square shape that brings the inlet and outlet too close together so that the incoming cold water mixes with the remaining warm water, instead of staying at the bottom of the tank, like it did in the old heater.
  3. Even after running the main engine for an hour and thereby causing 180 degree F (80 C) water to flow through the heater’s exchanger, the water in the heater is barely warm. (We know that hot water from the engine jacket is flowing through the water heater because the Webasco heat exchanger cabin heater plumbed in parallel still works fine and puts out as it always has.)

The result of the above is that we can barely get two showers out of the new heater before the water goes cold. And this “intrepid Arctic sailor” is a real wimp about cold showers. That’s why Phyllis, who is made of sterner stuff, always gets the second shower these days.

Contrast this with the old Allcraft that would after just 30 minutes of engine run time, easily do two hot showers, (indicating an efficient heat exchanger) and then provide plenty of hot water for the dinner dishes a couple of hours later. Even after all that, the water would still be warm in the morning!

So, three issues:

  1. In our opinion, and from our experience, the Atwood heater is pretty much useless in a boat installation, although I guess it would be OK if you were plugged in at a marina most of the time.
  2. Can anybody recommend a water heater that actually works in the real world of live-aboard offshore voyaging in which shore power is a rare luxury that happens maybe 10-20 nights a year? It would be really nice, although not vital, if it was fabricated out of stainless steel too, like our old Allcraft. If so, please leave a comment.
  3. Does anyone want to buy a slightly used Atwood water heater? Oh well, I guess not. Me and my big mouth.

As usual with this type of post we will contact Atwood to see if they would like to comment.

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