Why would an internal plug have been glued in place to block a clean out below the kitchen sink?

[Bob Pond]

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

 

[Twowaxhack]

They installed the test plug so they could fill the system with water to test it for leaks.

After the test the plug should’ve been removed bore they installed the clean out. They never removed the plug.

Yes you can use a sharp flat head screwdriver and go around the outside of it to remove the plug. Just dont knock it down the drain.

 

[breplum]

It should have been a 2" cleanout to serve a 2" pipe. Layers of stupid.

 

[Twowaxhack]

The picture shows a 2" ABS clean out with the cap removed. As shown, there is a white plastic internal plug, apparently glued in place so that I cannot use the clean out. Why would the plumber have installed this white plastic internal plug? To use the clean out (the kitchen sink drains slowly even after I cleaned out the trap on the sink side of the clean out) should I just gently punch a hole in the white plastic internal plug?View attachment 43378

That’s 1.5” abs, not 2”.