Moen Shower/Tub Valve Identification / Water temp issue

Question

I am currently redoing the shower/tub surround, and would like to know what valve I currently have.
It is a Moen, and uses the 1225 cartridge (crystal pull out handle, pull for volume twist for temperature).
On the side, it looks like "85811".
The house was built in 2000. High-end materials were not used.
I ask about the current valve, because we are having a terrible time with controlling temperature. Even turning on the sink (hot or cold) will affect the shower temp, and things like dishwasher and clothes washer make the shower useless with all the temperature changes. But from what I understand, this valve is some sort of mixing valve that should be handling temperature fluctuations like this. If this valve does this, then would a fancy thermostatic valve accomplish anything? Or is there some other cause.
We have 2 shower/tub combos, and both behave the exact same way.

Jimmy Fix-it · Accepted Answer

This is neither a pressure-balanced or scald-protecting valve. It is very simple Moen mixing valve that mixes cold and hot and adjusts flow according to your manual input with the knob.
There are various tricks to help reduce the effects caused by other users; the simplest is to install a flow-restricting shower head.
Changing the valve for a pressure-balanced unit will help but only to a point. If you really want to solve the problem you need to take a hard look at your water delivery scheme and investigate options like up/down-sizing parts, adding a hot water recirculating strategy, etc. Maybe consult an expert (licensed and bonded reputable plumber sourced through personal recommendations).

HoneyDo · Answer

What you need is a thermostatic mixing valve. Good ones aren't cheap but they will do the trick. I was having the same problem in my house a few years back and when I remodeled the bath I put in a Danze and it works great. There are a number of good ones on the market but read the reviews. You get what you pay for.

Answered by HoneyDo on February 25, 2021

Moen Shower/Tub Valve Identification / Water temp issue

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