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Old 05-18-2011, 02:26 PM   #1
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Appalachian Campers
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Location: Dixie !! (north Georgia) USA
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Water heater

First trip of the season completed and water heater issue. Heater works on gas and electric. In fact when I pull the lever on the pop off valve it is very hot - just like it is supposed to be. When I turn on the hot water in either the bathroom or the kitchen, I get a slug of hot water and then it cools back off. It is not as cool as the water coming into the coach from the outside source or the holding tank, but not warm either. I have checked and double/triple checked and the valves for input, output and bypass are set correctly.
I can set the water running and close the input valve at the WH and the flow stops - just as it should. Same with the output from the WH. I figured the handle on the by-pass valve might be put on wrong. I opened that with the input valve closed and had water again flowing. So, all the valves work.
It appears from the water temp there is some mixing of the hot, but the full flow is not coming through the heater.
I have checked the outside shower, thinking there might be mixture there. Both hot and cold are turned off. I know water is gong to and coming from the heater, and the water is hot in the heater. I hate to drive nearly 200 miles to the dealer and find out I am missing something simple.
Is there anykind of valve in the heater that might be stuck? I know a TT we had had a back-flow preventer internal valve, but I cannot figure how that would affect this probem. Ideas, fixes or intelligent discussion greatly appreciated. Oh yes, Atwood 10 gallon heater.

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Old 05-18-2011, 04:03 PM   #2
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Ford Super Duty Owner
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I know you said you checked the three bypass valves at th WH, But are you sure the center valve is closed? It sure sounds like the center valve is open. Remember the two outside should be open and the center closed.

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Old 05-18-2011, 04:17 PM   #3
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Spartan Chassis
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Only backflow preventer/check valve I am aware of is OUTSIDE the WH in the plumbing (outlet) on the rear ...I don't see how the check valve could be a factor ...in fact, I totally gutted the check valve on the rear of my 10 gallon Atwood and saw no effect whatsoever in water temp (only catch is that I cannot winterize w/o backflow into the WH ...no sweat since I don't winterize). ...and you say you have checked the outside shower valves to ensure the hot and cold are both turned off and not passing water through due to the head shut-off being engaged with faucets on ...and have you checked the same on the inside shower ??

It does sound like a valve is turned wrong, or something is set up wrong...

Only other thing I can think off off-hand is if the WH has been pulled/replaced recently ...the water lines were hooked up backwards on mine so the cold inlet was at the top and hot outlet at bottom rather than vice versa.
Paul (KE5LXU) ...was fulltimin', now parttimin'
'03 Winnebago UA 40e / '05 Honda Odyssey toad
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Old 05-18-2011, 04:40 PM   #4
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Hi doc,
This is a shot in the dark, but I've seen the valve handle turn but the valve does not turn internally. Or partially turns internally. When you turn the valve handle, does it feel like the guts of the valve are turning?
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Old 05-18-2011, 07:23 PM   #5
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I am pretty sure all the valves are right. As described above, when I open the center valve the water gets colder than when it is closed. I think there is some hot water getting through, but I cannot figure out why it is not 'hot'. It was fine when I winterized last winter and I reversed what it did, checked the manual etc.
I looked at the sketch with the paper work and it shows an part called a "mixing valve" where the hot water should be coming out of the tank. It shows a line going into this round valve from a ball valve near the bottom of the tank. Something is telling me this is where my problem is although I cannot figure why the mixing would be taking place there instead of at the faucets. Calling Atwood tomorrow and get their opinion. The tank was empty all winter and I wonder if some sort of debris or corrosion as something stuck. May take this thing off and see if it is indeed stuck if Atwood can't figure it out.
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Old 05-18-2011, 08:48 PM   #6
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Atwood has a mixing valve mounted on the back of the water heater. It mixes hot water with the cold water. If it malfunctions you can get cold water out but the water in the heater is very hot. The other thing that has happened to me is the hoses on the back of the water heater get plugged up with calcium build up. My MH is only 4 years old and they were almost completely plugged.
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Old 05-18-2011, 08:55 PM   #7
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Cat is on to it. There are check valves in the back of the water heater that allows the water heater to be bypassed when winterizing. The check valves are plastic and get brittle from the heat and break.
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Old 05-18-2011, 09:13 PM   #8
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Ours was clogged at the mixing valve ,I drain the tank remove the Water heater , took off the valve and each back pressure valve. What I found was the inside on the tank had calseaum particals white junk blocking the mixing valve. Washed out replaced bypass valve and replaced. It works now but i will cut out of system when winterizing next year.
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Old 05-30-2011, 06:26 AM   #9
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Repaired - hopefully

It was indeed the mixing valve. I took the thing off, thinking I would replace it. Wrong! It is a Watts valve. I have the number etc, but Watts' web site does not show this model and it says they have changed the design. After getting all the connections loose and shrinking my arm to fit behind the tank through the access panel I was able to get it out and figure how to increase the water temp coming from the valve. Unable to determine what the malfunction was, I just opened and closed the valve several times. I left it several turns wider than it was and put it back together. Heated it up and in a few minutes I had hot water flowing. I did have to increase the temp a bit more. After a few gallons of hot water flowing, (fingers crossed) I hope I have it fixed. Now to see if the fix lasts. Thanks for all the good advice guys.

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