I recently moved to a house and decide to clean the shower drain for the first time. I discovered substantial buildup in the drain.

More concerning, there appears to be a gap between the drain and the pipe below. I believe more of the gap was uncovered as I cleaned, with some of the buildup falling away (note: I am not sure if the material filling the gap is the same as the buildup in the pipe). The build-up makes it difficult to see what is happening.

When I stick my finger in the gap, it feels like the outer edge of the gap is smooth (like plastic).

Is this gap something I need to worry about / repair? If so, how?

View of gap

I believe this drain was installed ~5 years ago, so it is surprising to see this much build-up. At what point is this build-up concerning and should I take care of it it?

view down pipe

  • how is the shower floor constructed?
    – Jasen
    Jul 24, 2021 at 5:12

1 Answer 1


In all likelihood there is no concern here. The drain unit is probably mounted to the plastic (probably ABS black drain piping) in a manner where the lower pipe is glued to a coupler that is on the outside of the pipe. The drain unit mounts inside that coupler from above but its bottom does not meet the top end of the pipe from below. This leaves that gap which has a diameter that matches the inside diameter of the coupler.

I tried to prepare or find a picture but quickly realized that a general answer was better because there is a large variety of shower drains that attach to the piping in various ways.

The crud buildup is probably due to a combination of the type of soaps, shampoos and conditioners used by the previous owner. You will want to do your best to remove as much of that as possible. You will also want to try to investigate if the crud buildup extends beyond the P-trap. If the trap is accessible from below (basement, crawl space or ceiling of next lower level) you should also take that apart and clean that out as well. If the crud extends beyond the trap then you may be in for a sewer line service by a professional with the proper tools to insert a cleaning wand down into the drain system.

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