Hi, for the past week there have been knocking sounds coming in the area of the drain in the guest bathroom. Most likely air. We have opened all faucets and let water flow for 15 minutes as advised by city water board. Has not helped. The noise is not constant but comes and goes throughout the day and night. What can we do? House is soon 6 years old and this is the first time. There is no clogging so we do not think that is the problem as the water runs out without trouble. Thanks for whatever advise you have.

Hi, for the past week there have been knocking sounds coming in the area of the drain in the guest bathroom. Most likely air. We have opened all faucets and let water flow for 15 minutes as advised by city water board. Has not helped. The noise is not constant but comes and goes throughout the day and night. What can we do? House is soon 6 years old and this is the first time. There is no clogging so we do not think that is the problem as the water runs out without trouble. Thanks for whatever advise you have.

There may be an air vent that is clogged. (bird nest)