Single handle kitchen faucet. Turned to cold water flows fine. Turned to hot the same flow the faucet vibrates a bit. Strange. Changed the handle from hot to cold, cold to hot, turned volume to high and back to low a few times, no difference.

I then looked under the sink cabinet and turned the hot side quarter turn valve on and off a few times, did the same with the cold side. Turned faucet back in same issue.

Then I decided to remove the faucet aerator. Once removed, I noticed some debris on it that is black in color and feels rubbery. Turned faucet back on, to cold to hot no problem. Put aerator back on without the debris and it worked fine.

So it's the black color debris that is blocking flow to the point that it is creating some back pressure to cause the faucet to hum and vibrate.

Any idea what this is?



Could this be some debris coming from the water heater?

Looks too big to be a faucet washer. If that came from the water heater, I don't think it would have been able to pass through the 1/4 turn shut off valve, it would have lodged in the pipe there. If I had to guess, it may be the rubber lining from the flex supply lines. If you have flex supply lines, I would replace them.

Don411 is correct, that's rubber from a flexible stainless supply line. Often used as feed lines to the sink and to the dishwasher, sometimes DIYers use them other places they shouldn't.