New mixer in second shower causing temperature control issues in first shower.

[Sam Jameson]

We converted a tub to a walk-in shower last year. Installed a new mixer, and replumbed the shower head. Everything went according to plan and we've had no issues. Fast forward to this year - we're renovating the second bathroom and installed a new mixer (just extended existing plumbing to a new area, no other changes). Now we're having serious temperature issues in the original shower. If the shower is running and you flush the toilet, you get scalded. If someone runs the sink in the kitchen for even 5 seconds, you lose all your hot water, and the bathroom sink won't get warm at all if the shower is running. What could be causing this??

 

[Plumber69]

If I understand right sounds like you may not have the new ones cartridge in and would cause a cross connection

 

[Sponsor]

 

[hj]

IF you have not finished the new shower, the "plumber" did not install either the cartridge OR the "anti crossover" plug in the valve.

 

[Sam Jameson]

Thank you both! This should sort itself out once we can rebuild the walls and install the trim then, right?

 

[hj]

It should "sort itself out", when the installer inserts the 'anti crossover plug' that came with the valve.

 

[Jadnashua]

FWIW, not all valves these days come with the anti-crossover plug...it's an optional extra. But, the simple fix if you don't have that would be to install the cartridge in the new valve body unless you do have the plug available. WIthout the trim on, it may take a bit to ensure it is in the off position prior to turning the water back on, or you may take an inadvertent bath!

 

[hj]

They may not if you buy the complete fixture, but then the cartridge is supposed to be installed.

 

[Plumber69]

This problem gets asked at least once a month on here