Just recently I've been hearing a thumping sound after I flush my toilet. Usually it happens when the tank is filling up and I am running my sink faucet at the same time. The thumping sound usually goes away after the toilet tank fills up. This happens with at least 2 or 3 of my toilets. The noise does not happen when I only flush the toilet and no other water is running.

I thought this might be a water hammer but according to another website, the hammering would only occur when the water is not running. (not sure if this is accurate or not).

Does anyone have any suggestions on what might be causing this loud thumping noise?

Thanks.

Water hammering occurs while the water is running and for a short time after the water is turned off. You were misinformed.

That's what I thought. I tried to drain the pipes to get rid of the water hammer but I am still getting the noises.

Draining the lines probably will not help. You can get the knocking noise by air that can stay trapped in the lines, or by pipes that are not secured and can move around. Unsecured pipes are hard to find and fix unless they are in an unfinished basement or crawlspace. Anti-hammer devices are available but require basic plumbing skills and tools to install.

Call around and get 5 bids for plumber to install a hot and cold Water Hammer Arrestor.
He will be installing 2 arrestors onto your main water lines in utility room near water heater.(usually)
I had some put in a few houses over time and i think the most i paid was 250 dollars. I'd rather be less 250 than flooded from broken line. Goodluck

This message has been edited. Last edited by: JB Builder,