Help! What to do with old drain pipes coming out of floor before repouring concrete

Hi there,

I recently bought an older home, and I am planning on having the basement floor repoured.

Before I do, I want to make sure the plumbing buried in the old concrete is good to go. There is a slop sink in the basement that I would like to keep there. It drains into an old cast iron pipe in the floor. About 2 feet behind the sink is a cast iron cleanout. I am sure it is connected to the sink, because when the sink drains, the water in the cleanout starts moving. There is a plug sitting next to the cleanout but it no longer fits on the old rusty pipe.

I am trying to figure out how these are connected/what the cleanout might be for. I am also trying to figure out if I should excavate and try to have it replaced before pouring the new floor, or just try to use PVC & some kind of coupling to lengthen the drain and the cleanout so they will stay over the top of the new concrete.

I also know that often when there are two cleanouts next to each other, they are part of a whole home trap. I know this is not the building trap as that exists elsewhere.

See my photos attached. Any thoughts? I have had several contractors through and no one seems to be able to tell me what I should do about this...

-Confused new homeowner

Is the cast iron in the floor your 4" main drain? Are there any other cleanouts for the house? Its hard to tell what size pipes are in pics. If its 2" it could be just for the slop sink. If so you could extend the sink drain up with plastic above the floor using a nohub coupling. If no water flows through the pipe unless its from the slop sink I would permanently seal the one in the floor because you can use the sink drain as the cleanout for the line.

I am addressing the cleanout
buy a wire brush, and clean the threads on the clean out
buy a threaded male adapter, thread into clean out
buy a fitting x female adapter
buy a threaded plug
this will extend your clean out above the concrete



for the sink drain,,,if you want to cap it
buy a jim cap,,

Thanks for your early replies. I think the pipes coming out of the floor are bigger than 2 inch--actually looks more like 3 inch. Is that possible? I can measure tomorrow when I am back there to know for sure. See a photo here that gives a little clearer picture.

I am realizing from your suggestions that I may have been mistaken in calling it a cleanout--I think it is actually a trap. I say this because when I first moved in, it was dry, but now when I run the sink it fills with water, and the water doesn't ever fully drain. It just stays sitting in there.

Does that make sense? And does it change your recommendations?

That’s a drum trap you have under ground. Basically that sink is being doubled ptrapped. I would excavate that out. In case you put another sink there in the future, I would take the drum trap out and repipe.

Thank you for this insight! We didn't know what it was, but that makes total sense. There was an old drum trap under the shower upstairs too, so it is consistent with the other plumbing in the house. I feel a lot better going in to excavate with an idea of what I will find underneath. Thank you!