I recently moved into a new condo with 2 kitchen sinks -- a main one and one embedded in an island. There's a lot going on under the main one -- the cold water is split so that it leads to the faucet and the fridge, hot water split to lead to the faucet and the dishwasher.
When I turn on the hot water all the way (so there's no cold water coming out at all) the valve under the sink starts to vibrate very loudly. It sounds like a bad muffler! And if I open up the doors under the sink I can see it vibrate very quickly. It's hard to tell if the noise is coming from the water heater (which is right next to the kitchen) or the valve itself or maybe both. If I twist the handle slightly to let some cold water out of the faucet too, then the vibrating and noise stop.
This does not happen on the other sink (which is on an island and has its own line).
Any idea why this might happen and want I can do to solve it?