What causes a hum when we turn on the cold water tap or flush the toilet and how can we get rid of it?
The hum is quite often called the "Moaner" caused by the water level in your toilet tank being a little to high for the filler valve or ball cock valve to regulate the valve to an off position.
When you turn the cold water on at the basin it releases the water pressure allowing the filler valve to fluctuate thus the HUM or MOAN.
HOW TO REPAIR:
1. Remove the tank lid. If the water in the tank is GRUNGY it should be cleaned. First shut off the water at the supply under the tank and flush the toilet this will empty the tank. Pour a warm solution of dish detergent or my cleaning formula into the tank and with a brush clean the inside and valve mechanism. Turn the water back on and flush toilet a few times till tank water is clean.
2. If your filler valve has a float arm grasp the float arm with right hand up close to the float, with left hand grab float arm next to the filler valve. Hold firmly with left hand and bend rod about 1/4" down with your right hand. (don't force the float ball ) This will activate the valve quicker and stop the hum.
3. It's always a good idea to replace the flapper valve at the bottom of the tank when doing this project. Shut the water off under the tank, flush the toilet and remove the flapper (black round flap at the bottom connected to flush lever) and take it with you to the store to get the right replacement.