I suddenly have low pressure on the cold side of a bathroom faucet. All other fixtures in the house have normal cold pressure. I changed the faucet cartridge and that did not fix it.

The shutoff at the fixture is a 12-year old gate valve. Is that the next most likely culprit? Supply pipes are 1/2" copper.

run the cold with the cartridge removed...

Thanks. Before I try this, could you explain why? And also, how exactly would I do that, given that the faucet handle attaches to the cartridge?



Edited 1 times.

you turn the water off and on with the valve under the sinkee
you need to know if there is sufficient water flow into the faucet.

Given that I already replaced the cartridge, I've established that it is not the cartridge - and is thus the faucet, flexible supply, valve or copper supply line. If I were to remove the cartridge and shoot water up out of the faucet making a mess in the bathroom, I don't see how that would narrow anything down. I could see where disconnecting the flex supply under the sink would at least help determine if it is an issue with the faucet or before the faucet ...