My shower control is the single-handle type. Turn it a slightly to get cold water and turn it 180 degrees to get full hot water. I notice that if I connect the cold water line but do not connect the hot water line then the valve does not let any cold water go through regardless of the valve handle angle. Is this valve broken?
If you have a good supply of cold and hot water then it could be broken. Some of those have an anti scald setup but it's hard to tell what you have since you didn't give a make and model.
It is likely a pressure balanced faucet, which restricts flow when the pressure drops on either side to prevent scalding. Hook up the other side and see if you get anything. If it works, it isn't broken.
JK
Sounds like an anti-scald valve. It needs pressure on both sides to work. The object is if there is a pressure drop on one side, it shuts the other side down to minimize big temperature fluctuations. Most are adjustable to the maximum temperature it will allow. No, it is not broken.
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