Hot Water Back Flow... Bad Check Valve Somewhere?

[Tom SKP]

I recently emptied my hot water heater and flushed out the little bit of residue in the bottom of the tank. I then reinstalled the drain plug, pressurized the system, and then opened a hot water faucet until the air was out of the system.
Now I know that a small amount of air remains in the top of the hot water tank as a bit of a cushion, but here is what happens:
Previously when I turned my Shurflo pump off (no city water connected), I used to be able to get a cup or two out of the cold water faucet until there was no more flow. Now I get about 44 ounces. That's about 1.3 quarts, and it is mostly HOT water. The air cushion in the hot tank is backfeeding into the cold water lines.
This is a change from normal! Is there supposed to be a check valve in the cold water lines near the hot water tank to prevent this? Do I have a bad one?
Or is there something that would have caused the hot water tank to have a new huge air bubble?
TIA

Tom

[rockintom]

Quote:

Originally Posted by Tom SKP I recently emptied my hot water heater and flushed out the little bit of residue in the bottom of the tank. I then reinstalled the drain plug, pressurized the system, and then opened a hot water faucet until the air was out of the system. Now I know that a small amount of air remains in the top of the hot water tank as a bit of a cushion, but here is what happens: Previously when I turned my Shurflo pump off (no city water connected), I used to be able to get a cup or two out of the cold water faucet until there was no more flow. Now I get about 44 ounces. That's about 1.3 quarts, and it is mostly HOT water. The air cushion in the hot tank is backfeeding into the cold water lines. This is a change from normal! Is there supposed to be a check valve in the cold water lines near the hot water tank to prevent this? Do I have a bad one? Or is there something that would have caused the hot water tank to have a new huge air bubble? TIA Tom

First thing to check is see if both hot and cold spigots at outside (utility) faucet are closed. rockin'

[Tom SKP]

Quote:

Originally Posted by rockintom First thing to check is see if both hot and cold spigots at outside (utility) faucet are closed. rockin'

I see where you are thinking but no, all are closed.

Tom

[rockintom]

Tom, I'm drawing a blank based on your description. To the best of my knowledge the Atwood system doesn't use a check valve on their WH like Suburban does. When the check valve fails on a Suburban it usually means no hot water at any faucet.

If I was there looking at it, I'd probably start by draining the WH and refilling the water heater. I open the pop off valve to allow the tank to vent and water flow out of the drain smoothly. Then leave the same valve open when refilling. I shut off he water off when water just starts to come out the valve indicating the tank is full and to achieve a proper air pocket for normal expansion when heated. Of course, close the popoff valve. May want to get it a shot. rockin'

PS. Don't forget to shut off water coming into the trailer and have the WH cool before doing any work on it. Just a reminder.

[Tom SKP]

Quote:

Originally Posted by rockintom Tom, I'm drawing a blank based on your description. To the best of my knowledge the Atwood system doesn't use a check valve on their WH like Suburban does. When the check valve fails on a Suburban it usually means no hot water at any faucet. If I was there looking at it, I'd probably start by draining the WH and refilling the water heater. I open the pop off valve to allow the tank to vent and water flow out of the drain smoothly. Then leave the same valve open when refilling. I shut off he water off when water just starts to come out the valve indicating the tank is full and to achieve a proper air pocket for normal expansion when heated. Of course, close the popoff valve. May want to get it a shot. rockin' PS. Don't forget to shut off water coming into the trailer and have the WH cool before doing any work on it. Just a reminder.

Tom, That's about how I do it too. It seems that somehow I have a much larger than normal air pocket cushion in my HW tank. DW agrees things have changed as we are used to doing this annually when we we drain and winterize and then re-commision the water system.

I guess I need to dump the HW tank again and refill and see if anything changes.

As for a check valve, I don't believe there should be one as the water pump does not like a system with zero air cushion. It will cycle on/off very quickly and that is not good. (I can prove this by turning off the 'winterizing' cold water valve at the HW tank inlet)

BTW, I have the Atwood GE16TE 12 gal (10 gal actual) water heater.

Sure would be interested if anyone else with similar HW heater could turn off their city water, release the city water pressure, then cycle their water pump on, then off, and then measure how much water can be optained from the COLD water faucet.

Tom

[Dunner]

I just checked my 6 gallon Atwood and I only get about a cup of water when the pump is just turned off. I serviced it about a week ago and let the water run till it came out the relief valve.

Turn your pump on and then pop the relief valve and let the water come out of it for a few seconds, close it and see if if works the way it did.

[Tom SKP]

Quote:

Originally Posted by Dunner I just checked my 6 gallon Atwood and I only get about a cup of water when the pump is just turned off. I serviced it about a week ago and let the water run till it came out the relief valve. Turn your pump on and then pop the relief valve and let the water come out of it for a few seconds, close it and see if if works the way it did.

Thanks for testing your 6 gal HW tank, Dunner. That sounds about right at a cup or so.
BTW, I had already rechecked the pop valve and got only water. When I get somewhere where I have water again, I will re-dump HW tank and try again. I may even put some blocks under the left side of the camper to tilt the HW heater a bit to get more air out.
I'll report down the road.
Tom

[Dunner]

You need some air in it so it won't go boom when the water gets hot and expands.

I looked for my Atwood instructions and either I didn't get any or they are out in the MH.
I'm sure Google could find them and explain exactly how it should be filled or serviced.

[Tom SKP]

OK, here is my update: Dumped and drained the HW tank again.
Here is what I did differently:

1) Put 4" wood blocks on under steet side tires to slightly rotate the HW heater so the water mixing valve (water flow exit location on tank) would be slightly higher
2) Refilled the tank using the Shurflo pump (previously used city water flow) and then let pump push air out of lines.

Anyway, the end result is that the apparent large air bubble is gone and the smaller air bubble only discharges about 2 cups of water, once the pump is turned off.

Not exactly sure what happened initially and what changed, but all seems to be back to normal now...???

Tom

[Dunner]

It's not that big a deal to do it again without the 4" blocks. You need some air in the tank or it won't have enough room for the water to expand when it heats up. No air - tank go boom!!!!

[rockintom]

Quote:

Originally Posted by Dunner No air - tank go boom!!!!

That's the purpose of the pressure relief valve to protect the tank. rockin'

[Dunner]

I just don't trust them.

[Tom SKP]

Quote:

Originally Posted by Dunner It's not that big a deal to do it again without the 4" blocks. You need some air in the tank or it won't have enough room for the water to expand when it heats up. No air - tank go boom!!!!

I don't have a zero air bubble, just a reduced one. Not a big deal to most folks, but I'm a boondocker always trying to save water, especially in the head. With a large air bubble I consume more water there than I desire.

And yes, my PRV works fine. If I have a cold HW tank and turn on the electric HW heater and don't crack a faucet a couple of times, my PRV will leak the excess pressure.

Tom

[bill dean1]

Hi:
Just drained my Atwood 10 gallon hotwater heater and reconnected drain plug. I had released the overflow value and now I have no hot water.... I'm not sure that when I released overflow value other parts of heater got wet, any suggestions.

Thanks