I just installed a new toilet flapper, and there is a thud that now occurs when the flapper closes (not water hammer; rather, it seems to be the result of the immediate stop of water flow from tank to toilet).

My assumption is that the flap is not staying open long enough, but adjusting the float to allow more water is causing the toilet to double flush. If i hold the flusher down longer, the flapper closes more gently with no thud.

I've also tried reducing the amount of water in the tank by lowering the fill valve, but that made for a weak flush.

The thud did not occur prior to replacement, and I can live with it provided that this thud is not going to cause damage down the road.

I am ultimately looking to know if the thud is cause for concern and if there are any recommendations/tips/tricks to get a forceful flush without double flush and flap slamming shut.

  • This is a water saving feature in some brands so if it’s yellow it stops the flush and saves water, if it’s brown to flush it down you have to hold the handle for 3 seconds. The 3 seconds was what I remember reading it may be different for different brands. – Ed Beal Jan 2 at 7:55

As long as the thud is indeed coming from the flapper (not the fill valve), I can't imagine this causing any problems. You're good!

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