Rapidfire hammer noise

[cmw]

About a year ago I replaced a 4" centerset with a new 4" centerset (cartridge design) on the bathroom sink and has been troublefree until now.
Now, when I turn on the cold water more than 1/3 open, I get a rapidfire hammering noise which stops if I reduce the flowrate. This problem doesn't exist with the hot water. Is this an early warning of the cartridge failing?

[Verdeboy]

It sounds like a rubber washer has come loose. You'll need to pull the cartridge to check. If there is a "bibb" washer on the bottom of the cartridge, you'll need to tighten or replace it. It may be another seal that is failing, however, since only the cold water is affected. Replacing the cartridge would be the surefire cure.

[Terry]

You can also check to see if the cold supply is open underneath the counter.

[cmw]

Right on target. Thankyou.
The cold supply was only partly open. I opened it more & the problem went away. Why did this "partly open" result in the hammering noise??

[markts30]

Loose washer on the shut off was banging against the stem/seat in the valve and vibrating the pipes...

[cmw]

Thanks for the info.