Water-heater
on a boat

I replaced my hot water heater during the fall and used Defender's Atlantic water heater and went from 6 to 12 gallons. The existing one was 20 years old and was a mass of rust. The water heater's measurements were a little larger than the specs from both Defender and Atlantic since the base is somewhat wider than the rest of the heater. I ended up having to cut a larger hole under the aft stateroom berth, but that was easily fixed with a bigger piece to cover the hole. Make sure you can get the larger heater through the hatch. I could get it through the hatch but couldn't get it aft to the aft stateroom. I had to lower it with the mizzen halyard through the coach roof. The distance or run from the engine coolant to the inlet is about 15 feet. Be sure to use good exhaust hose for this run from the engine to the heater and back and orient the water heater the right way or you won't get all 12 gallons of hot water. Also you might want to check the wattage of the heater element to make sure your breaker can handle it. I learned from my mistakes on the installation but it sure is nice to have more hot water. The engine should run cooler with the increase in the distance and cooling effect of the heat exchanger being a greater distance away.

For what it's worth ..., I would:

1. Move the heater.
2. Insulate the lines running to and from the heat exchanger.
3. Install a circulating pump in the line.
4. Install a coolant filter in the line.

The circulating pump can be of the 12 volt variety or 110 volt. I've used both without problems. I think the 12 volt is made by Johnson but as long as it's made for constant use you'll be fine. The 110 volt (which I use now) is a German product commonly used for hot water heating systems in houses.

The coolant filter can be picked up at any good truck supply shop and comes in two varieties - cheap and expensive. The cheap ones are recommended for starters as you'll find they plug up quickly if your engine is not new. The more expensive ones help keep the pH level and are selected based on your tests of pH. You won't find a diesel truck on the road today without a coolant filter so why don't we find them in more boats?

By the way, in addition to the pump ensuring that your coolant is going thru the filter, it also serves to reduce the time it takes to get hot water after you start the engines, and, keep the chill off your engine(s) when you're connected to shore power.

Our water heater of 17 years also died this year -- we've yet to cut it up so we can remove it -- but we have no plans of replacing it. We decided that once we're living on the hook, running the engine to heat the water was not an effective use of diesel: The water tends to cool down very quickly once you start to use it, as cooler water replaces the hot water in the heating vessel. We also do not take showers in the head, instead we have several 1.5 liter solar showers and take our showers in the cockpit (or use dockside facilities). We do like hot water though, especially for cleaning up greasy dishes and washing our hands. We found a 2 liter "air pot" -- those coffee pot things that use an air pump to force the water out, so you don't have to pour -- at a local restaurant supply store for about $50. It fits nicely in the galley and can keep water warm for about 24 hours (so we just boil an extra pot in the kettle in the morning).

BoatU.S. (acting as insurance agent) wants me to remove my Wolters LPG demand gas hot water heater for 'safety' reasons. This unit has performed flawlessly for 12 years. It is vented to the outside. Has anybody on the list had experience with this type of heater and is there one available that is 'insurance company' approved ? It is the NFPPA (National Fire something or other) that is raising the objection to these appliances. There are units that are approved by the Canadian Coast Guard and ones that are listed with the American Gas Association that are available. ...

It is probably the NFPA, which is essentially a watch dog organization for the insurance industry. These are the same folks that bring you the NEC (National Electric Code).

If you have an AGA approved unit (it will carry an AGA seal, probably stamped on the device), you should have no problem with the NFPA.