Delta Monitor 17 series with R1000 rough in valve. As we take a shower, the first 10 minutes or so are fine. After that, you slowly need to turn the temp control to the hot side to maintain the temp, but then eventually even that doesnt keep up anymore.

I initially thought it was a problem with the water heater, but as the shower gets cooler, the sink (same bathroom, 5' away) maintains very hot water....MUCH hotter than the shower

The cartridge is installed correctly. Ive made sure there is good flow through the valve (without the cartridge installed I opened the service stops and let clean water blow through). The cartridge does rattle if shaken while uninstalled.

Any ideas?

Thanks.

-Chris

 

Is it a new cartridge? If not install a new one...

Thats a thermostatic valve... They do fail...

 

It was installed back in December, brand new set.

I might contact Delta for a new cartridge anyway.....not sure what else it could be at this point.

 

I have the same problem. I even have hot water to the tub faucet but water quickly gets cold when I switch to the shower. I can have only the hot water knob turned on, no cold & I have good water pressure, but it gets cold within a couple of minutes.

I am not home & I cant say what brand system I have but on the tub I have two handles (for hot or cold) & a 3rd handle to pull out which directs the water from the tub faucet to the shower head.

The terms "valve" & "Cartridge" is whats throwing me off. Obviously, I am no plumber. Any help?

 

Have you tried resetting the hot limit? Pry off the cover on the temperature control lever. Remove the screw holding the handle on. You will see a black plastic gear - Lift it out and rotate it to the left. This will increase the amount of hot water you can access from the valve. It is an anti scald feature. It may be set too low and your inlet water is now too cold and is overpowering your hot water.