How to Close Off a Toilet Drain

There might be several reasons a toilet will need to be closed off or capped. In areas of flooding, closing a toilet drain will prevent raw sewage from flooding up and into the toilet, or perhaps the toilet is no longer needed in that particular area of the house. The seal will need to be both air- and water-tight to prevent both sewer fumes and waste water from breaching the drain. Most toilet drains are standardized, but on older or antique houses, there might be a difference in toilet drain circumference that must be accounted for.

  1. Remove the toilet. Turn off the feed valve, drain the water from the tank, unhook the feed line and remove the anchoring bolts with a wrench. Pull the toilet up and out of the way.

  2. Remove the gasket and its remnants from the toilet flange. A rubber gasket pulls out of the flange, but a wax gasket must be scraped out with a small putty knife.

  3. Measure the size of the drain hole across the top. Virtually all toilets will measure either 3 or 4 inches. This measurement will determine what size cap or plug you will use.

  4. Check inside the flange for threads. If there are threads, you will be able to use a threaded cap.

  5. Get the correctly sized fitting cap or plug. A cap will fit over the sides of the flange and a plug will fit inside the flange. Plugs are generally considered temporary whereas caps are considered permanent. Choose the right application for your needs.

  6. Pound a plug into the toilet drain with a rubber mallet. Most plugs are made of rubber but some are wooden. Pound on the top until the plug is firmly seated.

  7. Insert a twist plug into the drain and turn the center screw tight. You will be able to use your fingers to tighten the plug. Tighten the screw firmly for a complete seal.

  8. Turn a threaded screw cap into the drain. Coat the threads with pipe dope to ensure an airtight seal. Turn the cap firmly into place with your hand.

  9. Cap off the drain with a toilet cover. These are generally made of rubber or the cap is PVC with a rubber skirt. They literally cap off the drain while the skirt is clamped around the pipe with hose clamps using a screwdriver or small wrench.

  10. Things You Will Need

    • Wrench

    • Screwdriver

    • Small putty knife

    • Tape measure

    • Pipe dope

    • Rubber mallet

    • Toilet cap or plug


    There are many styles of toilet drains used in homes. Some, like a PVC drain, can be capped and glued on with no clamps at all. On pure copper drain pipes, a cap can be soldered into place. Choose the type of cap and/or plug that works best for your situation.