Inspect the bottom of the flapper and also the top of the flush valve for embedded dirt. A whining noise when the tank is filling is often caused by restricted water flow to the refill valve. How To Sanitize Rv Water Tank Cleaning Rv Water Tank Rv Water Rv Water Tank Water Tank Adjust the trip arm bracket and flange so they are parallel with the top of the tank. Noisy water tank filling . Googling the issue suggests that it could be a noisy floatinlet valve that needs replacing. Turn off the water to the toilet tank. A I assume it is the sound of water filling into the tank that you hear as opposed to water hammer which can cause the pipes to clang and clatter. Clean the fill valve seat or replace the fill valve. Metal pipes can make similar noises in situations where the water is heated beyond about 125 degrees. Check that your main shutoff valve connected to the toilet is fully open. The noise goes as soon as the float rises and starts to reduce the flow. Water ...