Shower water goes from very hot to extremely cold in less than 10 minutes.

[Manny J]

My first floor shower goes from very hot to cold in less than 10 minutes.

I changed the single faucet shower cartridge and adjusted the hot cold water level on it before installing (I've done this before on my second floor shower), but this didn't help.

I know it's not my hot water tank, because my second floor shower stays hot for as long as one needs it.

So if I changed the cartridge, adjusted the hot/cold lever on it and my second floor shower runs well. What else could it be???

Thanks in advance!

 

[Jeff H Young]

recirculating system?

 

[Sponsor]

 

[Manny J]

recirculating system?

I don't entirely know what that means. But I have a boiler.

 

[Weekend Handyman]

I am not a plumber or pro, but I had the same problem. Turned out to be the mixing valve, which mixes super hot water coming out of the boiler with the cold water, so the fixtures get water that is a reasonable temperature.

 

[Manny J]

I am not a plumber or pro, but I had the same problem. Turned out to be the mixing valve, which mixes super hot water coming out of the boiler with the cold water, so the fixtures get water that is a reasonable temperature.

Do you think that would be it though? because everything else gets a good mix. My second floor shower, my sinks, etc.

 

[Weekend Handyman]

Do you think that would be it though? because everything else gets a good mix. My second floor shower, my sinks, etc.

Sorry, must have read your post too fast. No, I don’t think it would be the mixing valve if both showers aren’t, doing it.

 

[Jeff H Young]

not sure on a boiler

 

[Jadnashua]

Some single handle valves, when they start to wear, can allow the cold to cross-over into the hot side. Water will flow along the path of least resistance, so it could take awhile, and may only show up in certain places, depending on the length of the pipes, size, and number of fittings that create more/less resistance.

So, if it's something like that, try shutting the wall stop off on the hot from single handle faucets to try to isolate it. Some people put a Y on their washing machine hoses to always get warm...that could cause your issue. If you have a shower head with a separate valve and you leave the main valve open, that creates a cross-over for other things in the home. While the shower is running cold, you could also go around to the single handle faucets and just feel them...if it's been cold long enough, and there's a cross-over this time of year when the incoming water is quite cold, the faucet body itself will get cold. If that's it, replace the cartridge of the offending faucet.

 

[Manny J]

Some single handle valves, when they start to wear, can allow the cold to cross-over into the hot side. Water will flow along the path of least resistance, so it could take awhile, and may only show up in certain places, depending on the length of the pipes, size, and number of fittings that create more/less resistance.

So, if it's something like that, try shutting the wall stop off on the hot from single handle faucets to try to isolate it. Some people put a Y on their washing machine hoses to always get warm...that could cause your issue. If you have a shower head with a separate valve and you leave the main valve open, that creates a cross-over for other things in the home. While the shower is running cold, you could also go around to the single handle faucets and just feel them...if it's been cold long enough, and there's a cross-over this time of year when the incoming water is quite cold, the faucet body itself will get cold. If that's it, replace the cartridge of the offending faucet.

The thing is that every sink and the shower in the second floor, will run hot/warm for as long as we need it. The shower in the first floor is the only water output where the water runs hot/warm for about 10 mins or less and then runs really cold. Just confused why it only happens in the first floor shower. Doesn't even happen in the sink that's right next to the shower. And I just changed the shower faucet cartridge.