Shutting off water to clean out shower cartridge.

[jayre]

Please see the attached photos of my shower. I need to clean out the cartridge (circled in yellow) inside that has trapped debris that blocked hot water from coming out. I shut off the main water supply but every time I loosen this brass unit, it still shoots out hot water. How do I completely stop this?

 

[GReynolds929]

With water off, and water heater power off if electric. Open an outdoor faucet and an indoor hot faucet, then open the volume control on the shower, let the water drain down. There will be some water that will still come out when the stop for the thermostatic valve circled in yellow is opened, have towels and or a shop vac ready.

 

[Geofd]

If your going to remove that stop,possibly check valve you should have replacement parts

 

[Twowaxhack]

If you have a hot water circulator pump, turn it off.