Plumbing expertise needed

[Bugsinrugs]

My tenant called to tell me he has hot water coming out of the cold water faucet. At first it was in the upstairs bathroom but is now happening downstairs in the kitchen. I have never come across this problem before. Maybe the water heater is set too high? Anyone with knowledge about this? Thanks!

[wilnj]

Where is the incoming service, has there been any erosion that would be exposing the water line? My sister in Southern California had the same thing and found the water line was just under the driveway about 6” deep but that wasn’t a sudden change.


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[carambola]

I'm just an idiot but the pressure at the domestic water heater seems to be overpowering the street pressure.

[Bugsinrugs]

Water line enters from the rear of the unit and no erosion noted. So far it’s only in one bath upstairs. Not in the other upstairs bathroom. It’s just started to happen at the downstairs kitchen sink. The bath upstairs has a separate knob for the hot and cold. The kitchen has a single handle mixer.

[Bugsinrugs]

Cold water still coming on in the shower. Single handle mixer there.

[Bugsinrugs]

Maybe the water heater needs an expansion tank.

[Mark Howard]

Similar thing happened to be a couple years ago. Tenant called and said he didn’t have any cold water. I was like wth? I’ve heard no hot water but never no cold water. I went over and sure enough, no cold water anywhere. Went out to the main service entrance and the water was hot coming out of the ground. Turns out, in the heat of summer, the nearby water tower gets so hot that it heats the water and the ground insulates and keeps it warm. Lasted for 2 weeks or so then back to normal. Prob not the case here but interesting none the less.

[rwest]

If memory serves, some fixture in the house has a faulty mixing valve letting the hot water back feed into the cold line. Suspect a fixture that has only one lever that controls the temp.

[sc_rufctr]

Probably not helpful but years ago I heard a story about a plumbing fault in a new house. Apparently the plumbing contractors forgot to install a check valve on the inlet to the hot water system and because of that the "bidet" sprayed 100% hot water when used! This over site led to an emergency room visit.

Like this one (note the flick mixer). Regardless of the adjustment only hot water came out.

[Bill Douglas]

Check the cold water expansion valve on the hot water cylinder. It's designed to let cold water ëxpand" out of the hot water cylinder as it heats, but this may be stuck open.

[Bugsinrugs]

Originally Posted by Bill Douglas

Check the cold water expansion valve on the hot water cylinder. It's designed to let cold water ëxpand" out of the hot water cylinder as it heats, but this may be stuck open.

Would this be at the faucet in the bathroom?
At the water heater?
Thanks

[LEAKYSEALS951]

The thermal/cold water expansion valve would be located near the water heater.

Here's a video of roughly where it is located. It's on the white lines going in.

One way to test this (I'm guessing) is to turn the offending faucet on and put your hand on the white feed line (the white line in the video where the dude is installing the valve)- yours may or may not be the same colors. The red line in the video is hot water coming out of the tank/ the white line is cold water goin in- but in my neck of the woods, we don't use red lines.) The white supply line should be cold, and should supply cold water to the hot water tank to be warmed. If the feed (cold water) line gets hot, it's backfeeding.



Honestly, I have no clue as to what is going on.
If this was my place- I would go about this something like this.

One- Go to the "bad " faucet. How hot is the "cold" water? How long does "hot" water flow out of it? Does it get hotter? colder? same? Evaluate after several minutes of running it. Also, how does the heat compare to full blast hot water ? Same? Scalding hot? luke warm? etc....

Two- Go to a "good" faucet. Let it run and run and run on. Does it eventually get hot? If so? How much compared to bad faucet? Give it several more minutes than bad faucet. Earlier, I had asked if the nearby bathtub in the offending sinks vicinity suffered the same fate. If I recall, you had mentioned "no." That's potentially a clue-basically, the supply lines to the bathroom of the offending faucet and bathtub are in close proximity. IF the offending faucet is being fed by hot water from the cold line- then- the bathtub cold line 'should' follow with hot water in short order if it is hot water being fed into the cold line issue. If the faucet runs hot and the bathtub runs cold-after extended running- that potentially points to a bad faucet issue (although I can't see how a dual knob faucet could fail like that in my peabrain mind).

Three- If good faucet gets hot, (or even if it doesn't) try to locate the cold water expansion valve. Once located, open the bad valve in the house. Does the supply line to the expansion valve start to warm up? In the thumbnail picture of the video I shared(scroll back up to the thumbnail pic), grab the white line under the "share" button on the thumbnail, or even further away from the tank as possible (such as where the share arrow points). Does it get warm? That should be cold water flowing in, not hot water coming back out.

Four- find the main line to the house. Run bad faucet. Does main line to house warm up by the feel of your hands? (warm water entering house- water tower hot (don't tell greta... )/shallow line in the dirt getting warm/ etc.)

Originally, I was thinking a failed single lever faucet was failing upstairs causing intermixing of hot/cold water, and, many times, houses will have all the same type faucets installed at the same time of building- meaning, if one goes bad, then, others will potentially suffer the same failure mode in relative short order), but you mentioned upstairs had two separate knobs (making intermixing a bit harder). Also you mentioned the downstairs offending valve a single valve- which means two different type faucets are failing- making me think it might be the valve/relieving bladder as culprit. I could see intermixing on a failing single lever, but not a dual knob. (perhaps I'm wrong).

If you don't have immediate access to the house, it might be easier just to call a plumber, but this is where I'd start. This might take some detective work. Not hard sleuthing, but it will take some time to diy.

This is not something I'd personally want to talk a tenant through if I couldn't do it myself ]

Basically, you are trying to sort out 1. Warm water pumped in to the house. 2. A bad cold water valve/tank issue vs. 3. A bad faucet (or faucets) 4. A lithium battery fire (or something heating the) supply lines to the offending water lines to the offending faucets. or a combination of all of the above.

Good luck
R

[Bugsinrugs]

Thanks guys… I’m going to go there on Wednesday. I’ll report my findings. It’s 130 miles away.

[Bill Douglas]

Originally Posted by Bugsinrugs

Would this be at the faucet in the bathroom?
At the water heater?
Thanks

At the water heater. There are two. The main one is the cold water expansion valve which is located near where the cold water goes in. then there is a hot water expansion valve where the hot water comes out. It's cheaper to lose cold water than hot water so this is at a lower pressure so it opens first. And the hot water one is so that if the cold water one fails the hot water one will work instead to relieve the pressure in the cylinder.

Good luck.

[Bugsinrugs]

Much appreciated

[Bill Douglas]

Originally Posted by Bugsinrugs

Much appreciated

Pleased to help. Hopefully this is what it is as it's an easy fix, by just swapping out the part.

[look 171]

Was there any plumbing work done in the past week or two? Has the tenant decided to perform plumbing art at your place. If left untouch, this should never happen. Mixing valve? Still, shouldn't happen. there has to be some cold water coming through, maybe warm, but not hot.

[Zeke]

I remember an addition I was building. I left for the day with the shower arm capped off pending tile. The valve was left open and they only had lukewarm water overnight. Pushed the valve closed and all was well.

Probably not what's going on here, but worth noting.

[Bugsinrugs]

Originally Posted by look 171

Was there any plumbing work done in the past week or two? Has the tenant decided to perform plumbing art at your place. If left untouch, this should never happen. Mixing valve? Still, shouldn't happen. there has to be some cold water coming through, maybe warm, but not hot.

Yes, it is warm not severely hot. I replaced the valve stems on the handles of the faucet a few months ago. That’s the only plumbing that had been done there for years. I had them turn the water heater down a bit to see if that helps. I am going there tomorrow.

[GH85Carrera]

Back in the stone ages when I was dating, I dated a chick that lived in a house built in 1930s era. Some previous boyfriend put in a really cheap blend faucet in her bathroom shower. It was letting the hot water into the cold water side. I never understood how there was more pressure on the hot side to force its way into the cold side. The good news for her was at some point in the history of the house a plumber put in shut off valves for the shower, and there was an access panel on the back of the shower wall in the kitchen dining room. I shut those valves, and all was well. Then I got to replace her shower faucet with a better blend valve.