Water under the bus?

I am finding water that is constantly leaking in a small drip like fashion from under the hot water heater area. I can find no evidence of water inside the compartment bay where the hot water heater is located. This unit obviously does not have a drip pan similar to a residential hot water heater but my first thought is that the water heater is leaking and that it is time to be replaced. Before I start disassembling all of my plumbing I would appreciate some comments from the pros as to what else I may need to look at or consider. Thanks.

Note: The water is not dripping from the drain tube located under the bus, but rather in an area about 8" diameter around the drain tube location.

There is a valve that is providing over pressure protection. That valve is probably leaking. When we drive the hot water tank is heated by engine coolant and that excess heat likely drives up the internal pressure.

Follow the hose that is dripping up to the heater and you will see the valve. It is available at places like Lowes or Home Depot.

Tony are you sure the "leak" is not condensate from you back CruiseAir? Before you go in too deep, I would be sure the rear CruiseAir is turned off for a day or so and see if you still get the drip.

Mel,

Trust me. Its the pressure relief valve.

Tony,

Ignore Mel (this time).

I will second Jon. I have the same issue with my Marathon. I just grab the pop off lever on the pressure relief valve and release a short burst of water. That usually fixes it. Someday I will fix it right.

Tony,

I'm following on here, and this may be of interest to all.

First, I think most of our hot water tanks are heated by engine coolant. If yours is not don't waste your time reading this.

Typically as the water heats it expands and that expansion has to go somewhere. If it cannot be accomodated, typically by an expansion tank then the pressure valve will release that pressure harmlessly. If there was no expansion tank or pressure relief valve the excess pressure would likely burst a pipe or the hot water heater.

But if the pressure relief valve is handling the excess pressure than it is probable the expansion tank needs to be serviced or replaced. The releif valve is not intended to be opened and closed a lot so it typically will fail after a while. To prevent that the expansion tank needs to have an air charge. On my coach (and Tony's, and Truks, and Orren's and Jim's, and any other with an expansion tank) the water system pressure should be bled down to zero, a faucet or valve should be left open, and via the Schrader valve in the top of the tank (beneath the plastic cap) the tank should be pressurized to the pump cut in pressure. Usually the pressure is around 20 PSI. That needs to be checked periodically, but you can tell if the bladder pressure is down because the pump will short cycle. I left out guys like Harry and Jack and Gary because I think the newer coaches have a Headhunter pump with an integral expansion tank.

So Tony, I like Jim S's solution which is to give it a few jabs to open it, because if it is just some crud that will flush it out. But to prevent it, air up the expansion tank bladder because when it gets water logged the only pressure relief is through the valve.

Jim S I don't know if Marathon has an expansion tank, and if not I don't know how they compensate for increased pressure.

Jon, yes there is an expansion tank. My expansion tank may not be working properly. The tank is 1.5 gallon. That makes the usable size for water about .75 gallon?

That sounds right Jim. The size only really matters to provide expansion for the hot water tank, and to minimize pump cycling. I think mine is at least a couple of gallons, maybe more and I can get two Headhunter flushes before the pump kicks back on. I think it is just providing a cushion. If it is water logged that might be why your valve is dripping. The volume of expansion from the HW tank is likely not very much, but if there is no place for it to go it has to drip from the pressure relief.

OK, OK, I'm one of the guys that didn't waste his time reading what Jon wrote. (only because I have a vintage coach)

Now, before you go as far as I did, listen to a thing to check(no matter that Jon is probably right, but maybe not this time).

I had a leak under the hot water tank for 5 years(very small) and I blamed it on the hot water heater. When I tested and retested the blow-off valve several times and I finally found something else to check.

I had the black water tank removed only because I found some water around that and found nothing.

Next, I turned off the water to the ice maker and it stopped. We saw some wetness at the front bottom of the refrig prior to shutting it down. After 6-8 months I got my ass in gear and decided to check and we found the hose leaking at the back of the refrig.

I'll bet it is the water supply to the refrig.

The knowledge found here is truly amazing. Jon was dead on the money. I couldn't see the hose from the overflow/pressure valve where it should protrude below the undercarriage of the bus, but when I felt up in the insulation I could feel the hose that lead directly to the pressure valve. I was unable at first try to break the valve loose from the hot water heater, so I will need to go back at that later today, but after reading more of the posts it sounds like I probably need to service the expansion tank which may be the real problem and not the valve.

Lew, thanks for the thought on the ice maker, I would never even thought of that as a possible problem. Thanks to all.