We have an 8-year-old house and recently, we’ve been hearing a low-pitched humming sound coming from our upstairs guest bathroom. There is no knocking or ticking associated with the sound, just a low hum and vibration. Both the toilet and shower faucet seem to cause the noise. Whenever we flush the toilet (the sound occurs after the tank stops filling) or turn off the shower faucet (regardless of how strongly the tap was running before we turn it off), we get a loud humming that lasts about 15 to 30 seconds. It’s seems to be getting stronger with time, and now it’s gotten so strong that I can feel the vibrations through the floor throughout the second floor of the house.

After we flush the toilet, I can make the hum/vibration stop if I turn on the bathroom faucet during the humming noise. Running the faucet helps slightly with the noise caused by running the shower, but the results are not as consistent. There is generally only a drop in the strength of the hum/vibration, but as soon as I turn the sink faucet off, the humming sound usually intensifies and begins again.

None of the other bathrooms, faucets, dish washer, or washing machine creates this sound. If it helps, I live in an area with hard water and we’ve had water softener for 2 years.

Any advice would be greatly appreciated.

Replace toilet fill valve. If you still have humming sound there is a loose washer in a stop valve on the cold water line to that bath.