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Old 09-26-2014, 02:24 AM   #1
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Question Plumbing Problem

We have a 38 foot Bighorn 5th Wheel, about 5 years old. Recently, we have noticed that the hot water for both sinks has very low pressure to none. Cold side is fine. This has happended in the last month gradually. It's almost like a valve has failed or there is an air gap when the hot water valve is on full. We get some hot water pressure when there is some mixing, but little to none on full. I know the fix is probably simple , but do not know what to attack here. Any suggestions other than calling a plumber?

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Old 09-26-2014, 02:37 AM   #2
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One reason could be an outside shower faucet in the on position.


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Old 09-26-2014, 03:46 AM   #3
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It's been several year ago so I don't remember all that well. I had a check valve that went bad on or right near the water heater.

What it would do was allow some cold water to go thru the hot side (not full stream) but no hot water.

I believe the valve was right at the hot water heater. It was about $12 and I replaced it.

Wish could remember better but that was in 2006 and was on a class A ??

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Old 09-26-2014, 01:59 PM   #4
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Shower valve is set to the correct position.

As for the check valve, all I notice at the water heater burner is a blowoff (pressure relief) valve. Where would the check valve be? Would it be behind the heater at the storage tank? If that its the case, I will have to figure out how to get there.

Thanks for the suggestions.
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Old 09-26-2014, 03:18 PM   #5
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Your check valve is probably going bad. Yes, easy fix, usually hard to get to.
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Old 09-26-2014, 03:32 PM   #6
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Check the hot water bypass valve. It may be partially turned to the off position. winterizing.

Have you flushed the hot water tank? You may have some scale that has come loose and is partially blocking the tube. (doubt this one)
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Old 10-02-2014, 09:19 PM   #7
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Yes it will be behind the storage tank part of the HW heater.
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Old 10-03-2014, 06:02 AM   #8
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It happened to me once. I had an air pocket in the washer line. Once a wash cycle was run it was gone. If it was gradual I think one of the above suggestions should work. HWT in my unit is not fun to work on. Good luck with your problem. Report back when you figure it out.
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Old 10-04-2014, 09:03 AM   #9
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Remove panel in storage area to get to backside of water heater. You should see 2 lines going into WH,, blue and red. The red should be your outlet and there should be a check valve in the water heater where it connects. This check is probably plugged or hung up. New check valves are available at all the big box stores. You need to be careful removing it because it is most likely plastic and will break, then you will have job of removing plastic from threads.

Let us know what you find.
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Old 10-04-2014, 10:12 AM   #10
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Originally Posted by Clifftall View Post
One reason could be an outside shower faucet in the on position.
No, that would not do it, that would result in not-hot water but not low hot pressure...

What would do it... Answer gummed up check valve.

There are basically 3 water heater bypass systems
1 Valve

On the single valve system the valve is a 3-way that is installed in the COLD water line it feeds water (Cold of course) into either the water heater or into a bypass line, this line is connected to the HOT (outlet) line using a simple "T" fitting.

A check valve between the water heater and the pipe prevents backflow into the heater, and if it gets gummed up flow OUT OF the heater as well.

The two valve system uses two 3-way valves one accepts water from teh bypass or heater and passes it on to the RV Thus no check valve is needed... However....

Three valve system uses simple on-off Quarter Turn (usually) valves, one in the cold, one in the hot and one in the bypass line, the bypass connects to hot and cold lines on the non-heater side of the other two valves. so no check vlave is needed... Again However.....

However..... They often put check valve(s) in anyway, sometimes not only on the outlet but on the inlet as well (Absolutely no reason to do that)

The hot valve gets gummed up with mineral deposits and does not open in many cases.

And if you have the 2 or 3 valve version of the bypass. The top (hot) valve might not be fully opened to the water heater.

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