Vent, Valve & Volt
Toilet flush is weak or won't flush all the way

You can fix this

Likely cause: a flapper that closes too soon, or the wrong size

If the flapper drops before the tank empties, only part of the water reaches the bowl. Adjust it, or replace it with the right size.

Why this happens

HomeTips lists a flapper closing too quickly as a common cause of a weak flush. Korky notes some flappers have adjustable bands or dials that control how long they stay open, and that the wrong size flapper gives an incomplete flush. Standard flush valves take a 2 inch flapper and larger ones a 3 inch.

How to fix it

  1. Look for an adjustment dial or float band on the flapper. If there is one, set it to stay open longer and test.
  2. If there is none, turn off the toilet's supply stop, flush to drain the tank, and check the flapper size against the flush valve opening.
  3. Replace the flapper with one that matches, 2 inch or 3 inch, and clip the chain with 1 to 2 links of slack.
  4. Turn the water on and test-flush.

If this does not fix it, tell the plumber

  • The flapper drops shut before the tank empties.
  • The flapper size, and whether you replaced or adjusted it.

Build the full list: what to tell the plumber.

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. HomeTips: Toilet has a weak flush
  2. Korky: Slow or weak flushing toilet

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