Hot water turns cold in shower

[Pristinephoenix]

So, we’ve just recently had this problem in our main bathroom of our house built in 1973. When the hot water from anywhere else in the house is used, and someone is using the shower, the shower water immediately turns cold. There is also an issue of the hot water not being as, I guess you could say, effective? You used to be able to turn both left and right handles on completely and the mixture was perfectly Shower temperature. Now, you turn the handle is completely on and you end up having to back the cold off a lot because there’s not enough hot water in the mixture. I should add also that it is a two handle faucet with a turn knob to turn the shower on. Last thing, I assume this is related… If you have the hot water on in the sink Fossett in the same bathroom, and then you turn the cold water on, the water doesn’t get warm. It’s either a very hot or very cold, but both of the levers won’t mix if you know what I mean. It doesn’t go 50-50; it’s just 100% or 100%.

What’s wrong? My husband is capable of replacing whatever needs to be done. He’s even done soldering work to repair existing pipe. We are just having a difficult time diagnosing this one.

 

[WorthFlorida]

What type of water heater? From a furnace or stand alone? Is it gas or electric if it’s a separate water heater.

You have a lot going on and hard to know for sure but it sounds like you have hot water and cold water mixing together somewhere and perhaps your hot water source needs replacing. But the cold water shock in the shower is probably the faucet itself. The rubber components of the valves do wear out and break down. The hot side could not be fully opening and the mixing of the water is probably going on also in the shower faucet.

The faucets in the bathroom are 45 years old if they are the original. Time to rebuild or replace them. I would start with the shower/tub faucet.

 

[Sponsor]

 

[hj]

do you have a pump connected to the water heater?

 

[Pristinephoenix]

do you have a pump connected to the water heater?

No idea.

 

[Pristinephoenix]

What type of water heater? From a furnace or stand alone? Is it gas or electric if it’s a separate water heater.

You have a lot going on and hard to know for sure but it sounds like you have hot water and cold water mixing together somewhere and perhaps your hot water source needs replacing. But the cold water shock in the shower is probably the faucet itself. The rubber components of the valves do wear out and break down. The hot side could not be fully opening and the mixing of the water is probably going on also in the shower faucet.

The faucets in the bathroom are 45 years old if they are the original. Time to rebuild or replace them. I would start with the shower/tub faucet.

Hot water heater is just a year or two old. It is a gas. Standalone. 50 gal. Just stinks now that when we do dishes, or laundry, or even switch the hot water on for a second in another area, shower goes cold. We plan on replacing the handles and faucet already, and the sink faucet probably needs replaced as well.

 

[Pristinephoenix]

Can anyone help? This sounds like a common problem when I talk to folks, but no one can tell me how to fix it. It’s a new problem. Hot water turns cold when it’s used somewhere else in the house.

 

[Jadnashua]

Have you got any single-handle faucets in the house?

Do you leave the water turned on for your washing machine?

It sounds like you have a cross-over between the hot and cold. The water will flow along the path of least resistance. IF there's a cross-over somewhere, with nothing else running, the shower may be fine, but then, another user disrupts the balance.

Some single-handle valves can allow an internal cross-over. If you have any, try turning the under sink shutoff/stop, off and see if the problem goes away. If so, you've identified the culprit that needs a new cartridge.

If you have added any shutoff, external to a valve that mix hot and cold, and leave the two stops open, there's your cross-0ver.

FWIW, as the weather cools off, the incoming cold water temperature drops, so full hot/cold mix will subsequently cool off, too. WHere I live, summer cold water inlet temperature may be close to 65-degrees, but it can be below 35-degrees in the winter...mixing equal amounts of hot/cold will be considerably cooler in the winter verses summer.

 

[Pristinephoenix]

No single-handed faucets in the house. All doubles. That is a good perspective about winter and colder water in general; however, it’s still 70 degrees here in Oklahoma and this situation has been occurring since probably August. We are planning on replacing the bathroom sink faucet and everything for the tub; guts/stems and all (I’ve personally never done it before, but I have seen pictures as of lately and I know there’s a sort-of stem in there). It all needs replaced anyway. Maybe, hopefully, that will alter something enough that we notice a difference.

 

[hj]

Doing that should have absolutely no effect on your problem, because it is being caused by something outside the faucet.

 

[Pristinephoenix]

Doing that should have absolutely no effect on your problem, because it is being caused by something outside the faucet.

Good to know . Fortunately it still needs done... what does it mean to have a pump connected to the hot water heater? You never clarified that.

 

[Jadnashua]

Some people that want 'instant' hot water, will use a recirculation system, which generally uses a pump to make that happen. WHen that is being used, they return the water (often) to the drain port on the water heater. It also then requires a check valve to prevent pulling water from both the top and bottom of the WH when using hot somewhere. After just a short amount of hot water use, the bottom port will be cold from the incoming replacement water, and if you can pull from both the top (where the hot water rises to) and the bottom, where the cold water is directed, your hot will become diluted.

A washing machine could act like a cross-over. Shut the supplies off and see if the problem goes away.

If the shower valve has a pressure balance valve, it might be partially stuck. Sometimes that's built into the main cartridge, on others, it's a separate device inside of the valve body. Isn't too common, but if you have a tempering valve either on your water heater or say to feed a toilet so it doesn't sweat, that could have failed. Where I live, a tempering valve is required as part of a WH install. Often, they fail to all hot, but I suppose, it could fail and mix in cold rather than letting the hot get through undiluted.