Level of water rises in floor drain a bit and then goes back down when basement toilet is flushed. Would this be normal. Thanks

  • You should really revise to tell us more about your plumbing (type, age, relevant quirks). The question is quite broad otherwise.
    – isherwood
    Feb 15 '19 at 15:51
  • Thanks for the reply. The floor drain was put in original in 1957. But a previous owner cut the stool in the floor at sometime. And wondered if the fluctuateing in the floor drain level after a flush, could indicate a problem with their work. The water does not leave floor drain during flush. Just rises a couple inches approximately and falls back. What would be your first guess to cause this. Thanks isherwood for the reply on this matter.
    – Kerry
    Feb 15 '19 at 22:30
  • Please revise to tell us....
    – isherwood
    Feb 18 '19 at 13:37

If your plumbing is up to modern standards you should see very little movement in the floor drain's trap water level. The fact that you do probably indicates poor or blocked venting, resulting in a vacuum situation. It's not really a problem, though, unless the flush pulls the water completely out of the trap, allowing sewer gas to escape into the room.

It's possible that there's a partial blockage downstream, but unless this is a new development it would be my second guess at the cause.


Some old homes have a trap where the waste pipe exists the building. A little mushroom vent on the lawn would indicate that. Unfortunately in most cases, someone at some point cuts them down and covers them. If that's the case, the pressure from the water traveling down pipe would cause the water in the floor drain to rise and then level off. If it's a bad or blocked vent it would usually suck down and then level off.

  • Thanks to both of you for your knowledge, and quick responses.
    – Kerry
    Feb 16 '19 at 17:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.