Toilet flapper — set chain slack to about one finger width

A new toilet flapper often still leaves the toilet keeps running if the chain is too tight or too loose. Aim for about one finger of slack between the lever and the flapper at rest.

One-finger chain slack on a new toilet flapper

1. With the tank lid off and water at the fill line, rest the flapper fully on the flush seat and look at the chain path to the trip lever.
2. Adjust so you can slip about one finger under a mid-chain link without lifting the flapper — taut enough to open on flush, loose enough not to hold it ajar.
3. Flush once and watch: the flapper should drop and seal within a few seconds without the chain looping under itself.
4. If the toilet keeps running with correct slack, check the flapper seal and seat cleanliness before shortening the chain again.

For the full walkthrough, including trimming the tail and fixing a weak flush, see how much slack a toilet flapper chain should have.

Honest stop: cracked overflow tubes, stripped lever nuts, or a flapper that will not seal on a clean seat need parts or a plumber — more chain clips will not fix a warped seat.

More help

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