Hello -

Thank you in advance for reading. I have a difficult plumbing issue. Two showers upstairs. Both are experiencing cold / hot water regulation issues, both issues started within 3-4 months of each other. Shower #1 either runs extremely hot (scalding), or extremely cold. Nothing in between. Shower #2 runs extremely cold only, no hot. Sinks in both bathrooms run both hot and cold water.

What I did so far: Shut off main water supply valve outside the house. Opened shower faucet to drain remaining water in pipes. Removed single faucet lever. Removed mixer valve.

Now this is the interesting part: When I removed the Pressure Balancing Unit (PBU) [the one with the two holes for hot and cold]
<img src="http://www.homedepot.com/catalog/productImages/300/39/39e1aa41-7338-414c-ad15-aa928c221629_300.jpg" />
PRESSURIZED water came bursting out of one side (the hot side). The water was warm. This is on the shower #2, the one that WASN'T putting any hot water out. NO water was coming out of the cold side.

1. What is the cause of these two showers with temperature issues?
2. Are the two shower problems connected? Coincidence?
3. Why is pressurized water coming out of the warm side when the main water supply (outside the house) was turned off?
4. Solution?

Any input is appreciated!

1. What is the cause of these two showers with temperature issues? Your cartrdiges need rebuilding
2. Are the two shower problems connected? Coincidence? Yes, indirectly connected but that is not the issue
3. Why is pressurized water coming out of the warm side when the main water supply (outside the house) was turned off? When you should down the main there is still pressure in your pipes and it builds further as cold water is heated and expanded in your water heater.
4. Solution? Buy two rebuilding kits.