The picture shows a 2" ABS cleanout with the cap removed. As shown, there is a white plastic internal plug, apparently glued in place so that I cannot use the cleanout. Why would the plumber have installed this white plastic internal plug? To use the cleanout (the kitchen sink drains slowly even after I cleaned out the traps on the sink side of the clean out) should I just gently punch a hole in the white plastic internal plug?

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1 Answer 1


That's a temporary cap, or "test plug", installed for either pressure testing or debris prevention. You can just knock it out if you actually need to use the cleanout.

Obviously try to recover the parts so they don't become a problem downstream. The outer ring will stay in place as it's cemented in. Since there's no water flow through that section it's not an issue.

  • 2
    Thanks for these clarifications. I drilled a small hole through it, then inserted the bent arm of a hex key to try to pull it back out. The plastic just cracked, but with pliers I was able to pull out the pieces. This is one of those things that should be noted in a user manual for the homeowner.
    – Bompata
    Commented Dec 17, 2023 at 1:46

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