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Toilet flapper — shut the water off and flush before a swap

Running toilet

Before you replace a toilet flapper, turn off the supply valve and flush to drain the tank, so you can work dry and see how the flapper seats.

diagram of toilet tank parts including the supply pipe and cutoff valve
Photo: U.S. Navy / Wikimedia Commons (Public domain)

Replacing a toilet flapper is easier with an empty tank. Shut the supply valve and flush first so you can see the seat clearly.

Drain the tank before a toilet flapper swap

  1. Turn the supply valve behind the toilet clockwise until it stops.
  2. Hold the handle down to flush and let the tank drain.
  3. Sponge out the last bit of water so you can see the flush valve seat.
  4. Swap the flapper, then open the valve slowly and watch the first fill.

Honest stop: if the valve will not turn or keeps dripping when closed, that valve may need its own repair — do not force it.

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