Shower Issue

About ten years ago I had a Price-Pfister single handle shower unit installed. After this installation the shower never got extremely hot. It gets very warm, but not hot. I have replaced the cartridge several times over the past ten years and it seems to work for a while (although it could be my imagination). The hot water service for this bathroom, another full bathroom and the laundry is by a single 3/4 inch copper pipe. I few week ago I noticed the water in the shower in question was very hot when the washing machine was cycling through a hot water load. I thought this was unusual. The next day when I turn on this shower in question I turned on the hot water in the faucet in this bathroom and the shower was hot again. It seems if I turn on the hot water on the washing machine, the other faucet or bath, or the faucet in the same bath the water in this shower gets very hot (as it should be normally). Any ideas what the issue is?

That is odd. One of those that you almost have to be there to look at the whole picture. Believe me I have seen some odd things. Sometimes it comes down to cutting a wall open. The trick is to put what you see and what you know altogether.

Can't see a damn thing from here. Sorry.
What type of PP valve you have. Pressure balance or Avante.
10 yrs old I guessing PB.


If a PB ; Then
I would think that during normal use the hot water pressure is higher on the hot side going into the shower valve. Therefore a lower restricted flow on the cold side would shift the balance spool to restrict the higher pressure of the hot side to balance the pressure causing the cold side to allow a higher volume of water through the valve thereby making it difficult to get a hotter shower.

When you open another hot outlet you reduce the hot pressure enough to shift the balance spool to allow more hot to mixed with the cold.

Just a thought.
See if you can determine if the cold has a restricted flow.
That might be a tough challenge.
Start by removing the shower head.
The flow restrictor in it can make it hard to tell with it on

Check to see if the valve has integral stops and make sure they are open 100%

Do you have a single Handle washing machine valve

The cartridge was never the problem with your shower faucet. The adjustable hot limit stop under the handle was not set correctly by the plumber during installation. I use a thermometer to adjust all my shower faucet installations to 120 degrees. Adjust the stop and you can get full hot water.

SHR said:

The cartridge was never the problem with your shower faucet. The adjustable hot limit stop under the handle was not set correctly by the plumber during installation. I use a thermometer to adjust all my shower faucet installations to 120 degrees. Adjust the stop and you can get full hot water.

Click to expand...

I removed the stop years ago.