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Install pressure-balance valves to keep temperature even

QuestionWe have two showers and both have a similar problem. When someone is in the shower and water is used anywhere in the house, the person showering is either freeze-dried or boiled. Do you know what the problem could be? Thanks for your help.

AnswerI just about fell out of my chair when I read your question, as it brought back memories of our old bathroom. The difference is that I couldn't tell if my wife was tossing cold water over the shower curtain or just flushing the toilet—both had the same effect. I know she's done both, but I just couldn't catch her in the act. When she flushed the toilet, I would first get freeze-dried and then experience a hot flash as I danced a jig in the shower—not a pretty picture. I wonder if she was trying to tell me something, like she wanted a new bathroom?

Now that I have remodeled the bathroom, installed a pressure-balance tub/shower valve, and replaced 90 percent of the galvanized pipes with copper, I have eliminated the problem altogether. I even went one step further and replaced the shower curtain with a door so I can keep an eye on my wife when she enters the bathroom.

All kidding aside, several things could be causing the problem. The shower valves may be subject to water restrictions, perhaps caused by galvanized pipes that are rusting shut, undersized water lines, a main water line shut-off valve that is not fully opened, or low water pressure. It's also possible that the tub/shower valves need a tune-up.

My guess, however, is that your shower valves are not pressure-balance valves. Installing one in each shower would help eliminate the problem. The valves balance the pressure on both the hot and cold sides to prevent accidental scalding or cold-water shock due to pressure fluctuations.

In our new bathroom I installed PricePfister's "diaphragm pressure balance valve" instead of Moen's spool-type because it seems, in my experience, to be more resistant to jamming from scale deposits and debris in the water and it allows larger particles to pass through than spool valves. Now when my wife wants to get cute and flush the toilet, I don't worry about pressure fluctuations.

I suggest that you first verify that your main shut-off valve is fully open and then test the showers; if the problem still isn't corrected, have your plumber assess the situation and install pressure-balance valves.

It may be possible to install the valves from the backside of each plumbing shower wall. However, if framing studs block your access, the valves will have to be installed from the front side, meaning that the walls would have to be opened up.

Installation from the backside usually means that wall repairs can be made at minimal expense. Depending where the shower walls are located in your home, you could install pre-made plastic access doors to provide easy access to the shower valves for future repairs. A product such as this also eliminates wall repairs because the wall only needs to be opened up enough to accommodate the size of the access door. Available in different sizes, access doors can be purchased at any home center or plumbing outlet. Please let me know what approach solved the problem.

Copyright © 2004, 2006, & 2008 LAF/C.R.S., Inc. All rights reserved.
Question answered by Leon A. Frechette.

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C.R.S., Inc. · Spokane, Washington · USA

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