Toilet flapper — hold it closed to confirm a leak
Running toilet
If a toilet keeps running, hold the toilet flapper closed by hand to confirm a flapper leak before you replace parts — one beat.
When a toilet keeps running, guessing at the fill valve wastes parts. Lift the tank lid and gently hold the toilet flapper closed on the flush valve. If the run stops while you hold it, the leak is at the flapper seat — not a mystery in the supply line.
Hold the toilet flapper closed to confirm the leak
- Remove the tank lid and watch whether the water line slowly drops or the fill valve chatters on again after a flush.
- With clean hands, press the flapper flat onto the flush-valve seat and hold it closed for about thirty seconds.
- If the tank stays quiet and the water line holds while you hold the flapper, plan a flapper clean or replace — the seat path is the leak.
- If water still drops or the valve still runs with the flapper held closed, look at the fill valve and overflow next — do not only swap flappers.
Honest stop: if the flush valve seat is pitted or the tank has a hairline crack, holding the flapper closed is only a test — the seat or tank may need a plumber.
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- Related fixes elsewhere: Toilet keeps running — flapper check first · Toilet still runs after a new flapper