Upstairs shower running out of hot water almost immediately

Question

I have old copper piping through most of my house. When I get a leak I just replace part of the old copper pipe with pvc.

Most recently I had a leak in my hot water side and changed out a portion of my hot water pipe that leads to my upstairs shower. After that I lost water pressure in my kitchen sink and my upstairs shower runs out of hot water almost immediately however if you flush the toilet you can get more hot water.

I have replaced the water heater and that didn't help my problem. I also checked to see if my pressure balance valve was stuck but my faucet is so old it doesn't have one.

What is my next step?

Answer 1

You just replaced the tank so it shouldn't be a broken dip tube as I had first assumed. My next thought is there might be a blockage somewhere, but you should notice that as a loss of total pressure (compare the flow rates of your hot and cold coming out of a faucet somewhere).

You should probably remove your shower valve's cartridges and clean them while you're purging the entire system and flushing out debris.

I have a single handle shower valve that doesn't get as hot, or for as long as I'd wish, so I have cut back the cold water by closing its supply valve a little bit. This adjustment alone has increased my acceptable temperature dilation from ten minutes to upwards of half an hour.

Answer 2

It may be possible that you introduced some air into your hot water pipes somehow... perhaps it is not completely air locked, but you have just enough air to cause issue. This might not be the case, but an easy way to get rid of some air bubbles would be to turn on all the faucets (hot water) to try to blow the bubbles out. Otherwise, there are other tricks (see video) for dealing with airlocked hot water pipes.