RV Plumbing ?

[GW208]

We ran into a little problem with our bath and kitchen water faucets last week that we have never seen before and I was wondering if anyone has any ideas. We are getting hot water from our cold water valves. When you first open the cold water tap, it will run hot water for about 10 seconds before it gets to cold water. With the tap closed, it doesn't take very long at all for the cold water line to be heated again. The trailer was connected to city water if that makes any difference.

 

[Nigel]

Was the hose from the city water in the sun?

 

[GW208]

Was the hose from the city water in the sun?

I never even thought of that, but no the trailer and water hose were in complete shade. This is definitely hot water from the water heater.

 

[PBJ2500CTD]

My first guess would have been the hose hooked to the city water. It can get pretty warm, even in the shade.
Another thought would be the water heater by-pass valve not being fully opened/closed, causing a back flow into the cold water line when the water in the tank heats up and expands.
Or, is there a anti back flow check valve that is malfunctioning?

RV Doctor - Basic RV Water System & Check Valve Placement

RV Water Heater Bypass Systems

 

[Hoefler]

Check your shower valves, sometimes if they are on but the shower head is shut off, hot water will back flow through the shower valve into the cold line.

 

[GW208]

Check your shower valves, sometimes if they are on but the shower head is shut off, hot water will back flow through the shower valve into the cold line.

Thanks for the reply, but I'm pretty sure that's not the problem. Just out of habit, we always leave the shower head open with the valves at the sink closed.

 

[tkerrigan]

Try this, disconnect the city water hose, open pressure relief valve on water heater until water stops coming out, snap relief valve closed a couple of times. Hook city water back up again. Air pad may be gone out of hot water tank. Needed for expansion of water. This should be done about once a month.

 

[GW208]

My first guess would have been the hose hooked to the city water. It can get pretty warm, even in the shade.

Another thought would be the water heater by-pass valve not being fully opened/closed, causing a back flow into the cold water line when the water in the tank heats up and expands.

Or, is there a anti back flow check valve that is malfunctioning?



RV Doctor – Basic RV Water System & Check Valve Placement



RV Water Heater Bypass Systems

Thanks for that link PB, this is an old Wilderness trailer and there are no check valves or bypass valves that I can see. It looks like we should at least have a check valve on the cold water inlet to the heater. I am going to install one and see if that fixes the problem but it is odd that we have not seen this problem before.

 

[PBJ2500CTD]

Try this, disconnect the city water hose, open pressure relief valve on water heater until water stops coming out, snap relief valve closed a couple of times. Hook city water back up again. Air pad may be gone out of hot water tank. Needed for expansion of water. This should be done about once a month.

A most excellent suggestion, Tom.

 

[GW208]

Try this, disconnect the city water hose, open pressure relief valve on water heater until water stops coming out, snap relief valve closed a couple of times. Hook city water back up again. Air pad may be gone out of hot water tank. Needed for expansion of water. This should be done about once a month.

Thanks Tom, I like your idea. No cost and minimal labor. I've never heard about an air pad in the tank, but will try this tomorrow. We only use the trailer a few times each year so I always drain the tanks and heater after each use. When I refill the heater, I turn on the pump or city water and open a hot water valve until I get clear water and no air. Should I be refilling some other way to maintain an air bubble in the water heater?

 

[tkerrigan]

The fill is just fine, this problem only comes up after a couple of weeks or so. The air pad gets absorbed into the water, then when you use a fair amount of hot water, the cold water drawn in to the tank needs a place to expand to as it is being heated. There is a check valve on the city water hookup so it can't expand back up the fill line. I can tell when mine needs done as a hard squirt of water comes out when you open a faucet about 20 minutes after a shower. Sometimes it will leak out the water heater relief valve if all the air is gone.

 

[tkerrigan]

I forgot to mention, when draining the water heater down through the relief valve, open the closest hot water faucet to the water heater. Drains much faster.

 

[GW208]

The fill is just fine, this problem only comes up after a couple of weeks or so. The air pad gets absorbed into the water, then when you use a fair amount of hot water, the cold water drawn in to the tank needs a place to expand to as it is being heated. There is a check valve on the city water hookup so it can't expand back up the fill line. I can tell when mine needs done as a hard squirt of water comes out when you open a faucet about 20 minutes after a shower. Sometimes it will leak out the water heater relief valve if all the air is gone.

I wasn't able to try this out today because I forgot that I had the refrigerator out for repair and cannot turn the gas on. I will still try this Tom, but it sounds like it is more of a problem with extended or full time camping. I filled the water heater one afternoon last week and we noticed the problem the next day.

 

[DennyDay]

Sounds like a check valve problem - - when the water heats up it expands and backs up in to the cold water side

 

[BIGNASTY]

check valve

On my TT water heater there is a check valve that prevents that from happening the valve wont let hot water into the cold system even though the line is in the circuit and it wont let the water heater heat when empty and ruin the heater hope this made sense it didnt to me when the Mech at the RV shop I go to sold me a new valve and it worked great.

 

[GW208]

On my TT water heater there is a check valve that prevents that from happening the valve wont let hot water into the cold system even though the line is in the circuit and it wont let the water heater heat when empty and ruin the heater hope this made sense it didnt to me when the Mech at the RV shop I go to sold me a new valve and it worked great.

It seems that most likely what I need to do is install a check valve. You wouldn't happen to know what the brand of the valve you installed was, would you?

 

[rrl989]

Do you have an outside shower option? If so, check those valves, if not, then disregard and good luck.

 

[BIGNASTY]

The brand that my TT came with wasnt made any more the RV shop I use sold me another brand Im sorry I cant tell you the name but it did require some fitting on the plumbing to be changed. It was a male female kind of change nothing big at all

 

[TLane]

I owned an old house once that had a similar problem. It turned out to be a leak in the hot water pipe. It soaked an area underground and heated up the cold water pipe. It had the same symptoms - if you turn on the cold water you'd get hot water for a few seconds, then cold. I didn't discover what caused it until months later when the leak got so big that the crawl space was flooded. Hopefully, this isn't your problem; leaks in a travel trailer are usually more obvious.

 

[GW208]

Thanks for all of the suggestions guys, I ordered a Camco brand back-flow preventer that I found on Amazon and will see how that works.