mystery leak

[MudDog]

Originally Posted by MudDog

This reminds me of an issue I had at home.

Our city water meter does not have a back-flow valve (new meters are required to, but the older ones don't have it).

6-7 years ago I installed a security system and decided to buy a WaterCop water valve. I programmed it so when I arm my security system "away" the water to my house is shut off and when I disarm "home" it turns the water to my house back on. I don't have to worry about leaks or burst pipes when I'm away. Outside sprinklers are before the valve, so outside still gets water.

Anyway, shortly after installing I started getting drips from the pressure relief on the hot water heater. The water cop valve was preventing back-flow as the water/air in the hot water heater tank expanded and it had no where to go so the pressure relief did it's job. I ended up buying a small hot water heater expansion tank so the pressure had a place to go and that solved the problem.


In your case it's intertesting that the fittings hold pressure when running cold water thru, but can't seem to hold the pressure when the hot water heater water is expanding. Also interesting that the fittings are failing before the hot water heater pressure relief valve.

A few years ago, I installed a Shurflu accumulator tank on my TM to quiet and minimize the water pump when dry camping. It's installed after the pump. The pump has a back-flow valve.....so when there's expansion from the hot water heater it is pushing back and hitting that back-flow valve and everywhere else in the loop finding the weakest point to relieve the pressure.

Assuming there is not something wrong with the hot water heater (i.e. run-away thermostat, etc), I wonder if installing an accumlator tank would give the pressure a place to go (like an expansion tank for a household hot water heater)? The accumator tank would be in the loop whether running on pump or city water.

Searching the internet for differences between accumulator tanks and expansions tanks gives conflicting answers....

In searching more I have found several references to rv leaks only when the hot water heater is on.

I would say:

1) reset the air pocket in the hot water heater (see link below)

2) replace the pressure relief valve with a properly set replacement and reset air pocket

3) try installing an accumulator/expansion tank if you still get leaks when hot water heater is on.

The PEX is holding the pressure of city water when the hot water heater is off, correct? So it's only when you are getting expansion from the HW Heater. If you fix one connection, it's just going to find the next weakest one to leak from. Eventually it may get to the pressure relief valve (where it should) but by then you may have replaced every connection in the TM.

I believe the PSI on the accumator tank is normally much less than the city water PSI or the pressure require to trip the hw heater pressure relief valve...so if it holds city water pressure, it should be able to expand into the accumlator tank when needed.

If you dry camp, it's a nice add-on anyway to keep the pump cycling down.

Here's a few threads I found:


http://www.outbackers.com/forums/ind...?showtopic=660

Here's how to reset the air pocket that is supposed to be in the hot water heater to allow for expansion:

http://www.rv-motorhome-answers.com/...r-heaters.html

and a couple more links discussing expansion tanks:

http://www.marxrv.com/plumbing/plumb.htm

http://www.marxrv.com/hints.htm#expansion

Originally Posted by Redhawk

Dave, I found those washers at ACE hardware. I'm not sure if all ACE stores carry them, but the one in South Fork Colorado does.

I was trying to find replacement washers - or even the entire plastic piece (though it sounds like going with brass is the way to go if the whole piece needs to be replaced.)

John - do you happen to have a part number or description / size that would identify the cone shaped washers. we have several ACE HW stores in the area and it would be easier to make some calls first.

thx

It will take some work to correct the high pressure problem OR the leaking connection problem. You probably would want to know what way to attack the problem by taking a pressure reading of the system with hot water. Like MudDog said fixing the leaks will do no good if the presssure is still high, the next weakest connection will leak.

I haven't actually had the hot water heater connection apart, so my comment on missing teflon tape was premature. Please tell us what kind of fitting it actually uses, pipe or washer.

My guess is it's a pipe connection, not a washer. Redhawk has done the repair, so hopefully he will say.

The connection into my hot water heater was threaded, then immediatly into an adapter for a PEX connection that used a washer. This was on the Elk. If I remember correctly, it was basicaly the same as on the back of the Thetford (Elk). It took me 2 trys to get the leak stopped, and it was the pipe sealant on a new piece that made the difference.

Sorry, I don't have any part numbers for the washer, I just ask for the cone washer used in 1/2 inch PEX connections. The guy took me right to them. It was an ACE that had a lot of RV parts. I'd think that RV service centers would have them too.

You are correct that you have to buy the whole assembly at Home Depot to get the washer. Done that! I'm planning on going over there in October, if you are still looking for some then, I'd be glad to get them for you and mail them if I/you can't find them locally. LMK

A person could get rid of the adapter piece and just use a PEX to thread fitting. The only problem is once you tighten the fitting at the hot water and then crimp on the hose you can't tighten anymore because it will twist the PEX hose. (you may need to tighten more if the initial torque wasn't enough and there was a leak)

But if the leak was from no teflon on the threads then the washer may be reused.

[HIKERZ]

I too have a leak in the same place-it is where the hot/cold feeds are joined-unfortunatelt there is not enough room to pull out the insert box-I will have to take it to a dealer for repair

Can you clarify what you mean by where hot/cold feeds are joined - Are you talking about the mixer in the faucet itself or the hot and cold supply lines to the faucet?

Mystery resolved (mostly)

Thanks to everyone for their insightful input. I finally have plugged all the leaks and thought I’d share my findings.

The leaks in my TM I believe were simply the result of poor initial assembly, or less likely that several of the swivel nuts worked themselves loose. To recap, I observed an initial leak on the cold supply of the external shower. After disconnecting the ext shower and capping the supply lines, I found leaks from the hot supply line to the internal shower, the cold supply to the water heater, the hot output from the water heater, and at the output of the water pump. (All leaks occurred when the hot water heater was running.) I fixed all the leaks using various methods. At the input and output to water heater I added Teflon tape and tightened the swivel nuts thoroughly. I used pipe dope (for plastic pipes) for the connections to the internal and external shower and tightened the swivel nuts thoroughly. At the water pump output I simply tightened the swivel nuts (didn’t want to take that apart unless I had to). I suppose the bottom line is that properly tightening the swivel nuts is enough though I see no harm in using some pipe dope or Teflon tape for good measure.

All leaks stopped but now the t/p valve started dripping – quite a lot. About a drip per second for many minutes.

I then hooked up a pressure gauge to the hot water line feeding the external shower since that was still relatively easy to get to. With all other leaks now fixed, the pressure built to 142psi at which time the t/p valve began to drip. The drip continues until the water heater kicks off and the pressure drops a few psi (takes several minutes). I thought this was a problem but when looking at the Suburban manual, it claims that in an RV (closed system) the pressure will exceed 150psi at which point the t/p will leak. I consider this within measurement error of my setup. Hot water temp was ~135F (t/p spec’d to leak at 210F). These measurement and observations were consistent using either gas or electric heat and after insuring a proper air pocket in the tank.

So now everything is operating as designed, but I really don’t like the amount of water that drips from the t/p valve. The water ends up draining through the metal seam made by the water heater itself and its frame. From there it must go down the inside of the wall and out the bottom near the front of the wheel well. This can’t be good for the wall.

One way to avoid the t/p drip is that anytime the water heater runs, flip any water valve open for a second and relieve the pressure. But of course that’s not always practical. For now, I cut a sponge and wedged it in the bottom of the frame (see photo.) I was a little concerned about the sponge catching fire or a wet sponge accelerating rust on the frame itself. That said, I’ve checked the sponge several times and it’s not really all that hot except where the water is directly dripping onto it and it never expands to the point where it gets close to open flame nor the gas line vent. This seems like a better option than having water dripping down the inside of the wall.

As anyone else found their t/p valve drip that much? …and does the water drain out the same way? It really seems like a proper drain path should have been established for this.

-mike