shower not mixing enough cold water

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DIYGST

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Normally we have to turn the valve to 80% to get perfect temperature for our toddler using the hand shower. Today I noticed it was running extra hot like it is as hot as the water heater. I had to turn the handle about 20% to get some regular warm water.

Does anyone know if a valve can suddenly do this, hopefully the cold water is not leaked behind the wall. I didn't hear or see a leak, so it seems the valve is not letting enough cold water through. This shower valve was working perfectly for years. I checked the cold water pressure of other fixtures nearby it is the same. The hot water just go a lot hotter at the shower? (but the heater dial has not changed!)

I know the pfister valve can usually have an adjustment, or if I need to replace the cartridge.. does anyone know how this handle comes off?
 

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hj

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You pull the black plastic bar off and the screw is underneath it. It has a pressure balancing spool and if that is sticking, it could affect the temperature.
 

DIYGST

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Thanks, I got the cover off and screw removed, but the handle won't budge when I pull it outwards, is it just stuck?

Also, I found out this is called the body guard model. I have seen your post on other forums a bit of info about the guts.

The symptom seems to be that it will turn to as hot based on how much you turn the handle, but it will not cool down when dialing back. It has to be completely off to reset, to get warm water now, we have to set it about 30-50% and wait for the water to get warm but be sure not to make it hotter after it has heated up.

Is there a spool I can adjust or need to replace the cartridge.. etc? I am going to call PF tomorrow and see if they have replacement kit for it, it's actually the most precise valve I have used as far as dialing in hot water.
 
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DIYGST

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Just did a bit of investigation, the cartridge seems to be
974-491

made by aftermarket?
Generic Price Pfister 974-491 Faucet Cartridge -By Plumb USA 34400

on another site, it says it's been replaced by this
974-042

http://www.homedepot.com/p/Price-Pf...974-042-131765/205383569?N=5yc1vZc68oZ1z13yyx

all included one piece just need to attach the 4 screws.

Anyway, after looking at the design of the cartridge, it seems there is a diaphragm and a tube sliding left and right, I guess it has trouble moving back after the hot side has been pressurized. I feel a little better understanding how this balancing mechanism works and thinking less about water blowing behind the walls. But will talk to PF tomorrow to confirm part numbers.
 
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Jadnashua

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A pressure balance spool valve needs to move freely in the valve body, otherwise, it can disrupt the water flow and hot/cold adjustments. But, pressure differences between the two supplies can also be affected by your supply pipes, especially if any of them are old galvanized steel pipes. Those can rust up internally, making the flow volume quite small. OFten is worse with the hot water supply. Any time you try to open that valve when you have one supply off, it will push (or try to) the spool valve to the max. If that doesn't happen often, there may be some crud accumulated in there that makes it stick. Most cannot be taken apart, and when this happens, you have to replace it.
 
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