Hot water from the cold faucets!

OK, i need a little advice. A friend recently had some plumbing problems and I offered to help. She has a 3 story townhouse with a gas-fired AO Smith hot water heater that is about 9 years old. Recently, the TPS valve began to leak - it would gush quite a bit of water outside. So i replaced it with a new one.

At the same time, I checked the pressure in the expansion tank, and water came out of the valve - clearly the bladder had broken. So i replaced the old 5gal one with a 12gal new one and pressurized it to 60 PSI before refilling the tank.

Ever since then, hot water comes out the cold taps, typically after a shower. And it is HOT and takes several minutes to flush out before cold will come out. All the taps show this.

Here is what else i have done:

> She has two single handle shower with Moen posi-temp valves; i replaced the cartidges in each with new ones. One was originally installed backwards (hot and cold reversed) and also seemed to be broken - a few loose parts were rattling around. In either case, I have replaced both.

> Her input pressure from the city was about 80psi measered at a cold water hose bib, which seemed high, so i reduced this to 60.

> I dropped the HW temp from 150 to about 130 to be a little safer and save some money.

> I installed a check-valve on the cold water feed to the HW heater, in case it was backing the water into the cold line. When i feel this pipe with my hands, it does not seem hot once i get a foot or so away from the tank and the valve.

Here's what else i have tested:

> I turned off the HW valve on the feed to her single handle kitchen sink (Price Pfister) and the HW feed to her washer and the problems still occurs - eg, run all the hot out of the cold lines, run some hot, wait a bit, and the problem is back. All the rest of the faucets in the home are two-handled and mix in the spout, so i don't think there is a way hot could be leaking to the cold via those.

> I felt each cold feeder to the faucets and can't find one that is especially hot which might indicate where the hot water is crossing over.

> I turned off the hot water output at the HW heater and ran each faucet's (and shower's) hot water to see if any cold was leaking thru - none was.

There are no accessible cut offs to the two showers, so as i noted, i have replaced both catridges with no effect. She has a kitchenaid dishwasher but that (i believe) has just one water feed. She has a jetted tub with a two-handled tub spout - could there be a problem with it? I can't find any shutoff valves for it in any case. She has no water softener. She has a fridge with an icemaker but this should have just a cold water feed.

This problem did not used to occur. I can believe that the expansion tank failed and that cause the TPS to leak and perhaps broke an internal valve, but i have replace or turned off everyone i can get to and the problem is still there.

Any advice??

Thanks!

Mike

Try lowering the pressure in the exp. tank to 50#. Then see what happens. I don't think it will make a difference.... but maybe it is not opening. It sounds like you may have a cross connection at a faucet.

Hook up the pressure gage and After a shower let the heater work and shutoff then see what the pressure is.

hot from cold

well, i tried the tank at 40# before i raised to 60#...same symptoms.

I will check the water pressure at the HW tank in any case.

washing machine???

do you have a washing machine in the house??

I have tangled with hot water backin g up into the cold
lines through the washing machine before....

turn of fthe stops to that fix ture and see what happens.....

hot from cold

yeah i tried that - turned off the taps to the washer...still happens.

Some of the single handle faucet cartridges can be a source of cross-over, including the one for the shower/tub. Try turning the supplies off one at a time and see if that does it.

Does she have a hot water recirculation system?

hot from cold

thanks for the reply

She does not have a recirc system.

I have shut off the supply to the single handle in the kitchen. No change.

I can't shut off the supply to the two showers that have one-handled controls, other than by turning off the mains. But i have replaced each cartridge to a new one. No change.

Mike

When you say townhouse, I assume you are talking aobut a condo or otherwise "common wall dwelling". If this is true, check with neighbors to see if anyone has done any remodeling, or has had anything repaired, or replaced. I have seen where a crossover existed between units, and habits minimized the effect for some time. It's a stretch, but at least rule it out by checking with the others in the building.

With the water heater's gate or ball valve shut off , is there any water coming from the hot water taps? (cold or hot)

hot from cold

yes one wall is shared. I will ask that neighbor but i don't think so.

I have shut off the hot, left the cold on, and tested each faucet to see if any water comes out the hot - none did (except what drained out iniitially)

is there such a thing as a dishwasher with dual hookups?

All dishwashers that I'm aware of only use hot - there is no conection to the cold side.

hot from cold

OK, that is what i thought...still searching for answers!

Mike

Is the expansion tank on the hot or cold side? Is it downstream of the check valve and shut off? Pull it and plug the tee to see how that affects things. Where is the pressure reducing valve?

If you still cant find the problem, I believe you have to keep looking for something that has changed. I'd be looking for a cross connection that is associated with recent work. As I mentioned, I have seen two apartments that shared the same hot water circuits, even though they both had water heaters. I'm sure it was done by accident, and it took a lot of head scratching to find it. Find out what the neighbors (up and down, as well as same floor) have done recently. Make note of it regardless of how insignificant it may seem.

Also, if the stops for the washing machine are inopperative, you may think they are off, but they arent. You may try to remove the hoses to make sure the stops are working. As for the shower valves, pull the trim plates in the shower and look to see if that valve has built in stops. (you will see screwdriver slots on the valve stems).

Remember... if there were no solution, there could be no problem. (I dont know if that makes any sense at all, but at times like this I always mumble it to myself)

yeah...I wonder about whether those two apartments may have an interconnected piping system and yet seperate WH.......and its pulling hot thru the cold feed. I would check just to rule it out.....when you locate the problem be sure to post.

If there is a cross connection with the next condo you should be able to rule it out by shuting off your main shutoff to your condo. Then turn on a hot and cold faucet. Give the exp. tank enough time to push out it's water and if you still have pressure you have a cross connection with the other side. If your pressure drops to 0 then you don't.

hot from cold

GoTanklessToday said:

Is the expansion tank on the hot or cold side? Is it downstream of the check valve and shut off? Pull it and plug the tee to see how that affects things. Where is the pressure reducing valve?

If you still cant find the problem, I believe you have to keep looking for something that has changed. I'd be looking for a cross connection that is associated with recent work. As I mentioned, I have seen two apartments that shared the same hot water circuits, even though they both had water heaters. I'm sure it was done by accident, and it took a lot of head scratching to find it. Find out what the neighbors (up and down, as well as same floor) have done recently. Make note of it regardless of how insignificant it may seem.

Also, if the stops for the washing machine are inopperative, you may think they are off, but they arent. You may try to remove the hoses to make sure the stops are working. As for the shower valves, pull the trim plates in the shower and look to see if that valve has built in stops. (you will see screwdriver slots on the valve stems).

Remember... if there were no solution, there could be no problem. (I dont know if that makes any sense at all, but at times like this I always mumble it to myself)

Click to expand...

the expansion tank is right after the hot water outlet from the heater. the check valve (which i added) is just before the cold comes in.

i will check the washer stops and the shower valves

thanks

The expansion tank will wear out sooner being on the hot side...it is designed to be on the inlet (cold) side of the system.

One more question? Does the situation exist first thing in the morning when the owner first gets up and turns on cold water? If unknown, ask them to try that simple test first thing before any other water is run anywhere in the house. If the expansion tank is the culprit, the expanded hot water in the exp tank will have cooled off. Cold water should be cold if my theory is on track.

Put the expansion tank on the cold side, downstream of the shotoff and check valve. That is where is should be, (although the manufacturers like it when you put it on the hot side, as they wear out quickly and then you buy another). I bet a krispy kreme to a dollar that it will fix the problem. Also look at your check valve, make sure its installed correctly, and is functional.

hot from cold

thanks

i think they installed the expansion tank on the hot side because it fits better in the space - its under a stair and there is not a lot of room. It has been that way for 9 years, tho, and i just replaced it with a larger one (the old one failed). the problem is new so i don't think it is the expansion tank. I did tap on it and it is not filled with water in any case.

i added a check valve (just in case) to the heater input but that is also new and it did not happen prior. so i don't think that is an issue. I asked the neighbors and they have not done any work. plus i shut off the hot and cold feeds and opened the valves and if it was connected to the neighbors water should continue to run out, but it does not.

I put a pressure gauge on the HW drain to see what it read. It was 60 psi (same as input) at idle. I drained some hot water and let it refill and reheat...after 30 mins...60psi. So it is pushing the water somewhere.

FYI. I took apart one of the shower valves and there are no shut-offs, so i can't isolate those. But as i said, i just replaced those cartridges so i think the problem is elsewhere.

my latest test was turning off EVERY VALVE i could find - all the sinks, the washer, even the dishwasher. (The only thing I cannot turn off are the showers.) Ran some hot. Waited 30 mins....hot is back in the cold side. I really don't know what else could be crossing over.

any other good diagnosis techniques? i am thinking of running some hot out, letting the tank fill, and closing off the HW feed. That would ensure that NO water could bleed back in the cold feed from the HW in.

if the cold taps run cold first thing in the morning, then it proves where the hot water is coming from. After the heater heats up, hot water is filling the expansion tank. Using cold will allow the exp tank to push that hot water back into the cold stream and out the open faucet. The only stumbler is the check valve that you installed. Thats why i say you have to check it and make sure its working properly.

These are just theories, but I could be way off. put the exp tank over on the cold like i mentioned (even if its just temporarily with a flex connector) and see how that changes everything. If it doesn't , I'll be surprised.

Mike, it seems to me that if the problem started after you worked on the system then I would go back and check everthing that you did. Sometimes it's the simplest things that we overlook.

I would put everything back the way it was before you started.(Except for the TPR valve) If that solves your problem then I would start installing the "upgrades" that you made one by one, testing to see if the symptoms start again, after each step.

Good luck, isn't plumbing fun.