The hot water in my bathroom is leaking from the faucet. I've shut off the valve below the sink, but it continues to dribble out. Also, there appears to be some rust build-up. Could that account for a failing valve?
You have a broken seal in the hot side of the faucet. The reason the faucet still leaks when you turn of the hot supply valve is because it is coming from the cold side. Just turn off both valves to the faucet. Then remove the handle to the hot side. There should be a nut underneath that. remove the nut and pull the assembly out. It may seem hard at first but it pulls out. Look down in the hole where the assembly. There may be a rubber gasket there. Remove it and look at it. If it is torn, replace it. Make sure you get the repair kit for the faucet first. If it is just a cheap brand faucet, it will be better then to just buy a new one. The rust build up I would assume is because you may have galvanized water piping.
It sounds like you have some lime build up in the valves if you can't shut them off or the rubber gaskets inside the valves are worn. Valves are made of brass which doesn't rust. only steel and iron rust. Try tightening the packing nut. That's the nut just below the shut off valve handle. If that doesn't work shut the warter off at the water heater and take the valve apart. First remove the handle from the stem with a screw driver, next remove the packing nut (usually 7/16) then put the handle back on a turn it counter clockwise. Inspent the valve stem, valve seat and the rubber gasket or washer for wear. If you see any lime build up (it will be a hard white substance) remove it with Lime Away or one of those brands. It the valve is very old you may have to replace it. If you own the house replace the valve with a quarter turn ball valve, They are more expensive, but will last a lot longer.
In some homes where the sink is mounted to the wall, as in your case, there may be shut off valves in the basement directly under the bathroom. If there are none there then you will most likely need to shut off the main water the open the bath room sink faucets to drain off excess water. Good luck.
It sounds like your shutoff valve is not working properly. You need to shut off the hot water at the main valve where it comes out of the water heater (this will shut off all hot water in the house); drain the line (there's a little knob on the main shutoff valve you can twist that will allow the water in the pipe to drip out), then replace the shutoff valve. The shutoff valve is probably threaded pipe and can be loosened using two wrenches (hold the pipe with one wrench and twist the nut with the other - you want to conteract the twisting motion on the pipe so the pipe does not weaken and burst, which is why the one wrench needs to hold the pipe). once the valve is removed, clean the pipe threads with a wire brush and cleaning solvent to remove the rust and install the new valve. Be sure to read the manufacturer's directions to see if you need to wrap the threads with teflon tape first. When the valve is replaced, you can turn on the main hot water valve at the water heater; then use the new shutoff valve when you prepare to repair or replace the faucet. I would expect the faucet is leaking due to worn out washers, you can take it apart and tell. I susupect the rust you see is a result of the leak and not the other way around.
