How to Fix a Toilet That Fills When the Sink Is On


If your toilet fills when you run your sink, you probably have a clog in either the toilet or the sink. Unless your sink or toilet is backing up septic or sewage water, you can try removing the clog yourself by using a plunger. Never use a chemical drain clearer, such as Drano or Liquid Plumbr, in a toilet. If the water is dirty or foul-smelling, do not attempt to fix the clog yourself. Instead, contact a plumber as soon as possible.

Things You'll Need

  • Old washcloth
  • Bell-shaped plunger
  • Rubber plunger
  • Wet an old washcloth and place it over the sink drain.

  • Make sure there is enough water in your toilet to cover at least a few inches of a bell-shaped plunger. Position the plunger over the toilet drain, press down to ensure a good seal, and then pump the plunger vigorously 15 to 20 times.

  • Remove the plunger. If the water swirls down the drain, you are done. If not, repeat plunging until the drain is clear.

  • Remove the washcloth and set it aside.

  • Position the rubber plunger over the sink drain and press down to ensure a good seal. If you have trouble getting a good seal, fill the sink with a few inches of water and then place the plunger over the drain.

  • Pump the plunger vigorously 15 to 20 times.

  • Turn on the taps and flush the sink’s pipes with water for several minutes.

Tips & Warnings

  • A snake, or hand auger, can be used to remove a large or particularly stubborn clog. Use a 20-foot-long snake in a three-eighths-inch diameter to snake down the toilet and sink drains to remove any obstructions.

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