My upstairs shower gets little to no hot water pressure but full cold water pressure. Hot water pressure is fine in all other areas of house. What can I do please. Thanks

Sounds like some mineral build up broke loose and is njhow blocking the inlet ports of the shower valve. Shut the water off to the shower and open up the valve. Remove the cartridge and check and clean the inlet ports. NHow, turn the water back on for a few seconds to flush out the supplies and open valve body. Reassemble and test. Better now? This is caused by minerals building up in your water heater. Let me show you how to avoid this.

For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back togather the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps, Tom