NOTE: Older toilets used the force from a greater volume of water to remove waste, while newer toilets require adequate venting to remove waste.
The following symptoms are signs of a clogged waste stack or vent pipe:
- Water rising in the toilet bowl
- Slow flush (bowl water rises quickly, but falls slowly)
- Frequent clogs
- Having to hold the handle down to get a proper flush
- Sounds coming from other drains in the area when the toilet is flushed
- Bubbles coming from the trapway opening during the flush
One way to check the waste stack is to take a large bucket of water and dump it in the toilet bowl. If the toilet flushes well, there may be a restriction within the vent pipe that will need to be cleared. If the water still drains very slowly, there may be a clog in the waste stack.
An alternate way to test for a clog or venting issue is to check the P-trap.
NOTE: This test will not work if the sink's P-trap is not located on the same vertical waste stack as the toilet.
- Locate the P-trap below the bathroom sink.
- Place a bucket below the P-trap to catch any water that may spill.
- Unthread the P-trap at point 1 (Fig. 1).
- Swivel the P-trap pipe at point 2 (Fig. 1) to expose the opening from point 1.
- Flush the toilet five to six times.
- If the toilet flushes better with the P-trap open, the vertical vent pipe is blocked.
- If any debris comes out of the pipe from the wall, there may be a partial or full clog in your waste stack, or you do not have sufficient venting.
- If the P-trap method is not successful, contact a licensed plumbing professional.
1388573-10-B ©Kohler Co.