RV Doctor – RV Hot Water Heater Only Producing Small Amount of Hot Water

Tech Tips, Repairs, & Maintenance

March 26, 2009

352

March 26, 2009

Dear RV Doctor,

My girls and I just purchased a 1985 Minnie Winnie. We just took our first “shakedown” trip and discovered two issues. First, the hot water heater; the heater will light and produce hot water, unfortunately it is only about 2-1/2 cups (no warm shower for me)! I went to the RV store and was told to replace the thermostat and the overheating sensor, which I did. Nothing changed. Any suggestions? Secondly, the pilot light in the oven will light but not come up to temperature. I’ve been told two different things. First I was told that the thermostat was bad and needed replacing (very expensive) and second that the pilot light assembly needs to be cleaned. Care to way in on these two issues?

Stephanie Williams, (West Richland, WA)

Answer:

Stephanie, if you’re serious about only having about 2-1/2 cups of hot water produced by the water heater, I’d be tempted to suspect that your water heater is equipped with a by-pass valve system which isolates the water heater from the rest of the fresh water system for the sole purpose of winterizing. Isolating the water heater eliminates the need to fill the heater with anti-freeze during cold weather storage.

The valves will be located at the rear of the water heater; that section that extends into the motorhome. It will probably be located under a cabinet or closet. You may even have to remove an access panel to see them. Water heater by-pass valves weren’t that common back in ’85, but some astute RVer may have had an aftermarket set installed somewhere along the way. They are (or should be) pretty much standard now. Even with the valves closed, it’s still possible for radiant heat to migrate and heat a little of the water in the by-pass line.

If you’re being a little facetious, (easy to be with two daughters; I know, I raised two myself!), then I would suggest a possible blockage in the hot water line going to the shower. This can be verified if indeed you have plenty of hot water emanating from the galley or lavatory faucets, but not in the shower.

A third possibility is that you have an inordinate amount of calcium build-up in the heater tank due to lack of maintenance over the years. The water heater should be flushed and cleaned regularly to keep particles from coagulating inside the tank. This too can be verified by removing the drain plug located (or opening the drain valve) on the outside of the water heater. Open the pressure and temperature relief valve or open all the hot faucets inside the coach; the draining water should be clear and flowing steadily out of the drain opening. If it simply trickles and small white particles and a milky residue exists, then the heater tank may be full of build-up and the inner tank should be replaced or, because of its age, I would recommend a brand new water heater be installed. I’ve cut open older heater tanks in the past and have found some of them over half-filled with deposits and calcium-like chips. As for your second question… stay tuned for my post on March 29th!

(Please feel free to comment, however, please also note that due to the volume of communications I receive from multiple channels I cannot guarantee a personal response in every instance. However, questions of an overall general interest may be considered and published in an upcoming RV Doctor column.)