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Plumbing in the Home/mysterious screw below shower valves


mysterious screw
mysterious screw  

3 handle controls
3 handle controls  
"I'm trying to change out shower valves to stop a leak.  I have 2 questions: Could you tell me what this screw (see photos) is for?  There's one just below each shower/bath valve...the hot and the cold.  There may be one below the middle diverter but, if so, it's behind the tile so I can't tell.  I have a 3 handle  control (the middle one is the diverter) by Price Pfister. I'm attaching a photo of the 3 valve stems and second photo with a clear view of the hot water valve stem and the screw below it.    

And question #2: I turned the main water supply to the entire condo complex off and also I turned off the one in my unit just above the water heater in my unit.  The leak stopped.  Then I turned the main water supply to the entire condo complex back on but not the one in my unit above the water heater.  The leak started again.  The water that leaks feels cold.  Can I assume the problem is with the cold water valve stem?"

Hi Pat,
Sounds like your diagnostic skills are good. The leak is probably on the cold side.

The screws are called "apartment stops" and they are a way to turn the water off locally at the valve without turning off the whole building. Common in multi-unit buildings.

Since the valve and the associated stems and seats are all the same age, i would recommend replacing the washers and seats on all three valves. Hot, Cold and diverter at the same time since you will have the water off anyway. The "seats" are a replaceable metal ring in the valve body that the compression washer seals against. If the seat is worn or damaged, replacing the washer is only a short-term fix.

Good Luck,

Plumbing in the Home

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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