I've done a bunch of searches, no definite answers. I have a Atwood 6gal gas water heater. Trailer is 8 years old, no problems in the past. We camp a lot, and I have always done the winterization myself, so am familiar with the bypass valves. The first time out this year, I'm getting a few seconds of hot water out of the cold tap.
This is running from the onboard tank. I re-checked the winterization bypass, it is a 3-valve system. The valves to the tank are open, the third between the lines is closed. There is no outside shower to leave valves on, nor is the inside shower valves on.
I pulled the access cover to get to the WH, and the only thing I can think of is that there must be a stuck one-way valve, but I don't know if what I am looking at is a check valve, or just a 90-degree gray plastic tee into the water heater. No brass fittings anywhere. I just found a Atwood schematic online, and don't see any built-in on-way valves either.
Only other thought that comes to mind is that the 3rd valve which is now closed, is not closing completely?
After re-reading:
Just noticed that you said you are using the on-board water tank so this really doesn't apply, but down here it is very common for the water in the hose from the faucet to the RV to get pretty hot if you haven't used the water for a while. You'll get hot water from the cold tap for about a minute until it cools down.
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It does sound like the check valve into the hot water tank is not closing fully at this time. It might be a think that will clean itself with a few camping trips, or might not fix itself, and you will be left with a decision to open the back of the water heater to access the valve, or live with it and save $100 in parts and hassle. If a newer unit still under warranty, then parts are free, and labor too until it is a few months older, but it sounds like it is not a warranty issue, with your unit over 2 years old.
An easy fix is when you first turn on the water heater is to let it warm up a little bit, open a hot water faucet a small amount of lukewarm water out, then after 10 minutes let some more hot water out, as the water in the tank is expanding. Once the heater is warm, usually the water will not expand nearly as much as it will when heating from 55F to 140F the first time.
Also if you are sure the hot water heater is full of water, you can let it heat with the pump off, then it will have less pressure inside the tank to push back into the cold water lines.
Stopped at RV repair shop. Was told on a three valve system there is no check valve. No brass fitting noted either.
I restored the air bubble in the hwh. Made no difference.
Have noticed the waterpump runs longer after turning off faucet. It does not run when there is no demand. However it is the Shurflow smart sensor 5.7, which only comes on when there is flow. Not a pressure switch like the entry models. One thought is that the pump check valve is leaking back into the fresh water tank.
* This post was
edited 05/26/12 11:09am by djousma *
Golden_HVAC wrote: It does sound like the check valve into the hot water tank is not closing fully at this time. It might be a think that will clean itself with a few camping trips, or might not fix itself, and you will be left with a decision to open the back of the water heater to access the valve, or live with it and save $100 in parts and hassle. If a newer unit still under warranty, then parts are free, and labor too until it is a few months older, but it sounds like it is not a warranty issue, with your unit over 2 years old.
An easy fix is when you first turn on the water heater is to let it warm up a little bit, open a hot water faucet a small amount of lukewarm water out, then after 10 minutes let some more hot water out, as the water in the tank is expanding. Once the heater is warm, usually the water will not expand nearly as much as it will when heating from 55F to 140F the first time.
Also if you are sure the hot water heater is full of water, you can let it heat with the pump off, then it will have less pressure inside the tank to push back into the cold water lines.
Fred.
Thanks for the reply Fred. I don't think there is a check valve on my HWH. Very easy to access.
I restored the air bubble in the HWH for expansion. made no difference.
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