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kissiffer4 03-22-2011 10:14 PM

Check valve positioning - is this incorrect and could it cause a cross connection?

Here is a photo of our plumbing configuration next to our water heater:

On the far left is a 1/2 inch pipe, what we think is a return line. Next to that is the hot water pipe and to the right, the other pipe going in to the water heater is the cold pipe.

Now, behind the flue we have a check valve with an arrow pointing to the right ->, which is connected to the cold water line.

We have a weird problem with hot water running cold in our apartment (also only way to get continuous hot water downstairs is to leave the hot shower faucet upstairs running) and what appears to be a cross connection. We had a guy today take a look and he told us that the check valve was in the wrong position and ought to be located on the cold pipe closer to the water heater. Does this make sense? He said that in it's current spot, there is a chance of water running up the pipe and into the water heater so it ought to be located toward the base of the water heater.

One last thing. The return line and cold pipe are warm if we don't run water for a while, but today I ran the hot faucet for a couple of minutes in the shower and went down to the basement to check and both the return line and cold pipe were freezing cold.

So...I'm wondering if this configuration is correct or if indeed the check valve is in the wrong place, or might need replacing?

Any advice much appreciated. Thanks!

TheEplumber 03-22-2011 10:30 PM

Curious- do you have a recirculating pump on the 1/2" line?

kissiffer4 03-22-2011 10:43 PM

TheEplumber, I'm not sure about that. Is there any way to tell? I can track the 1/2 inch line out of the basement, but not further than that unfortunately. Gut feeling is it runs all the way to the 4th floor of the building. We are on the 3rd & 4th floors and the water heater is in the basement.

TheEplumber 03-22-2011 11:06 PM

Since you don't see a small pump on the 1/2" line near the heater I'm going to assume you have a convection type recirc line.
The check valve is installed OK. It keeps your cold water from entering the 1/2" hot return line. It can also be plumbed to the WH drain located at the base of the tank.
I'm guessing that either the check valve has failed or you might have a bad cartridge in one of your single handle faucets that is allowing hot and cold water to "cross connect" upstairs. Kinda hard to say without being there, and I'm tired cuz I've been up since 3am :yawn:

SuperPlumberGuy 03-22-2011 11:19 PM

The green thing with the arrow on it is a pressure reducer not a check valve. The thing to the right of that is a backflow preventer. What you are looking at is the feed for your heating system. I am sure this has nothing to do with the problem you are having with the domestic hot water. The problem you are describing sounds like a cross connection most likely at a mixing valve or the washing machine.

TheEplumber 03-22-2011 11:25 PM


Originally Posted by SuperPlumberGuy (Post 615046)
The green thing with the arrow on it is a pressure reducer not a check valve. The thing to the right of that is a backflow preventer. What you are looking at is the feed for your heating system.

OP said his check valve is behind the flue

SuperPlumberGuy 03-22-2011 11:33 PM

oops....I assumed they were talking about the combo fitting in the picture. Mea culpa

TheEplumber 03-22-2011 11:38 PM


Originally Posted by SuperPlumberGuy (Post 615051)
oops....I assumed they were talking about the combo fitting in the picture. Mea culpa

I stared at the picture for a long time. Had to read the post again before I caught on. But I agree that its a mixing valve someplace.

kissiffer4 03-23-2011 07:33 AM

Gents, indeed, the check valve is hidden behind the flue. The plumber we had come in to check out the problem was pretty convinced the check valve was causing the problem. He thinks it is in the wrong position. I'm a newbie to this sort of thing so I'm really not sure.

I thought it might have been the washing machine, but after shutting off the hot and cold to the machine we still had the same problem.

Could it be the check valve is faulty?

Also, if it might be a mixing valve some place, where could that be?

Any suggestions? Thanks.

Dougtheplumber 03-23-2011 11:05 AM

Close the 1/2" valve that is barely visible behind the hazardously installed vent for the water heater, this will isolate the recirc line and possibly rule out any problem with the check valve when you run the water, see if there is any change
If that does not prove anything, shut off all the valves in the picture, turn the gas valve to pilot, drain the remaining hot water in the house from the tank drain leaving the tank itself as full as possible, take the union apart, twist the piping out of the water heater and check the dip tube, it may be broken off in the tank. It does not necessarily sound like a dip tube problem but in your case, with the union, it is an easy check and another thing to cross off the list.

the_man 03-23-2011 11:51 AM

if that 1/2" pipe is a recirc return, the check valve should be pointing to the right. however, you should also have a check valve above that 3/4x1/2 tee to prevent the hot water from traveling into the cold water system. the flow on that check valve will be from the ball valve to the w/h (arrow pointing down) but closing the isolation valve behind the flue would show you thats the problem. you can also close the feed to the w/h and open any 2 handle valve in the house to hot to see if any mixing valves have failed... with the feed off pressure should go away quickly

kissiffer4 03-23-2011 12:03 PM

the_man, interesting. I think that is exactly where the plumber said he wants to move the check valve (from it's existing position). His argument was that in it's current position hot water would be traveling into the cold water system. What I'm wondering is, even if this were the case, how would it explain the problem I'm having?

Would this cause the situation where I can leave the shower faucet upstairs running and get as much hot water downstairs as I like? (only if the faucet handle upstairs is directed towards hot, however - strange thing is, cold water comes out of the faucet upstairs if I leave it running like this).

He wants $650 to move the valve, but I think will fix the flue pipe at the same time.

I will try turning off the recirc. line to see what happens. If it is off, does that mean I ought to get constant hot water from the 2 handle valves (sink etc.)? If that is the case, would it indicate a problem with the check valve?

Thanks again for all the advice.

kissiffer4 03-23-2011 12:26 PM

Guys, I have added another couple of photos. This one is the on/off thing on the 1/2" line. I tried turning it anti-clockwise for ages, but it just kept turning and didn't seem to be going anywhere. Is it corroded?

This photo is a better view of the existing check valve behind the flue:

Any thoughts?

Cheers all.

Jackofall1 03-23-2011 01:31 PM

Have you closed the valve on the 1/2" line and tried it yet, I would without almost certainty that this is the problem. You are back feeding the hot water system with that 1/2", close the valve if you can and I would bet the problem goes away.


Edit - and you should be looking into fixing that flue arrangement, before you do anything else!

kissiffer4 03-23-2011 01:37 PM

Hi Jack,

Stupid question, but how do I shut the valve off on that 1/2" line? I tried turning the blue handle anti-clockwise for ages, but it just keeps twisting and doesn't seem to stop. Is there any way to tell when it is completely off? Should I be turning it clockwise?

Also, on the first photo, what is the blue valve to the right (under the green thing) and the blue handle at the top?

Thanks so much.

Oh yeah, the plumber said as part of the $650 for moving the check valve he would fix the flue ha. Pretty annoyed with the inspector we brought in to check the place out before we bought it that he missed all this stuff.

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