I just installed a new Kohler toilet. It flushes fine but after the flush the level of water in the bowl slowly drains. Why would this be and is it anything to worry about?

2 Answers 2


More than likely the tank is filling the bowl above the bowl's fill level, and the bowl drains slowly until it's level with the top of the trap (or siphon).

Toilet Cross Section

Unless it's completely draining, there's really nothing to worry about.

  • Nothing to worry about except wasted water (yeah I know global warming yada yada). Try lowering the level in the tank to save this problem from happening. Aug 23, 2015 at 0:08
  • 1
    @Dopeybob435, good advice. I probably should've added that in my answer.
    – BillDOe
    Aug 23, 2015 at 1:30

Could be a venting issue causing the siphon to live up to its name. That will normally result in a very low water level in the bowl. It can also allow sewer gas into the house.

  • A strong wind blowing over the top of the vent stack can cause quite a Bernoulli effect and literally suck the water out of the bowl. I've seen it happen in my own house, though it has never quite emptied it. I'm surprised they don't have a hat on them just to prevent that.
    – BillDOe
    Aug 23, 2015 at 1:40
  • Also, improperly installed back-to-back toilet stalls can suffer from siphoning, doesn't matter how large the stack is, the volume and speed of the water flush pulls more air than can be supplied, siphoning the opposite toilet. Aug 23, 2015 at 3:53

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