Thumping when Sink Running

[satellite_chris]

I get a loud thumping sound after several seconds of water when I open the cold valve on one sink in my bathroom. The hot water is fine as well as the cold water on the other sink, shower, and bath tub. I replaced the entire faucet with no resolve. I tried leaving all valves open slightly, turning off tha main water, and then turning back on minutes later....this didn't do anything....any ideas?

[jimbo]

Is this a single "thump" or a repeated sound when it happens?

Two things to check would be that the stop valve under that sink is fully open, and it is still possible that you house pressure reducing valve is bad, even though only this one faucet is afffected. Connect a gauge to the water line, and watch it as someone opens and closes that faucet.

[satellite_chris]

It is a repeating thumping very fast. Does that change your suggestion on using the guage? Do I do that at the water line entering the sink?

Thanks for the help
Chris

[Randyj]

Possible loose faucet/supply valve washer.... most likely a pipe bumping a stud or something like that...or a combination of those. You might try pulling the cold water valve stem them opening the supply line valve to flush the line. If you have a pressure regulator making adjustments to it might fix the problem. Running at about 45 psi seems to be about right.

[Cass]

Does the water pressure seem to change at all with the noise? It sounds like a loose washer.

[satellite_chris]

Duh, I should have added the most important detail. Once the thumping starts, the water stops coming out at all. Sorry for wasting everyone's time without that very important detail.

[Verdeboy]

Remove the cold water stem. The rubber "bib" washer may have come off completely and is vibrating and blocking the water. If that's not it, then you may have an obstruction in your supply line or shutoff valve.