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What is a thermostatic valve, what does it do?

Posted by mollyred (My Page) on
Sun, Jan 7, 07 at 22:50

I remodeled my bath a year and a half ago and installed a thermostatic rough-in valve (newport brass model 1-534) in the shower. I thought I knew what it was supposed to do, i.e., keep the shower water temp constant at the chosen temperature. My husband (installed after the plumbing went in)says it doesn't work, and today it didn't even serve as an anti-scald valve. (Guess who was in the shower when I flushed the toilet?)

Perhaps its broken, or perhaps I have it all wrong. What IS a thermostatic valve? What is it supposed to do? How does it do that?

Thanks so much!


Follow-Up Postings:

RE: What is a thermostatic valve, what does it do?

I'm just putting these in -- after rough in (and tile work) -- the instructions say to set the "temperature limit" using a thermometer. On my Kohler its a small ring with a set screw, I believe.

Anyway -- sounds like this might not have been done when the bath was remodeled -- probably easy to do. Get the manual for the valve. On Kohler you have to remove the handle to get to do so.


RE: What is a thermostatic valve, what does it do?

many people confuse pressure balanced and thermostatic valves. Pressure balanced are more common. They keep a constant ratio of hot and cold water when the pressure in either the hot or cold lines fluctuates. All have an "anti-scald feature". This is just some form of a stop to keep you from turning the temp handle all the way to hot. if you change water heater temp, the stop needs to be readjusted. many people just set the stop all the way hot or just remove it. some pressure balanced valves work better than others none are perfect at maintaining temp. all are better than the old plain shower valves.

Thermostatic valves come in two varieties, fancy expensive electronic controls(I am not familiar with this variety) and cheaper(but still expensive) valves that control hot and cold flow with a cartridge containing a heat sensitive material (usualy wax) that expands with heat and slows down the hot water. There is of course some lag in respose to a change in temp so this mechanism won't solve the problem caused by flushing the toilet unless the valve is also pressure balanced. I think most if not all thermostatic valves are also pressure balanced.

A pressure balanced valve is satisfactory for most people. The only advantage to Thermostatic is that you can turn the temp handle to a known position, and in a minut or two, your shower will be at the desired temp without any additional adjustment.

Now at last, too fix your problem. Remove the cartridges and anything else easily removeable from your valve. Soak it in lime away for a few minuts. clean any debrie off the valve. Make sure everything moves freely. let the cartrideges dry off. lubricate everything with silicon grease. reassemble.

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