Slab level cast iron drain? Best way to cap / seal?

[n0sleeves]

Hi all. I have a 4" cast iron drain hole that's level with a slab. Right now, I have a capped 3" PVC pipe in going into it, but there's some wiggle room between the cast iron and PVC. A 4" adapter didn't fit. Need to seal it to keep out the gases and prevent leaks if there's ever a backup. The iron isn't threaded, and I don't want to mess with the slab. There is a raised floor that will going over it and will not accessible without demo.

What's the most peace of mind / best way to seal this up? Liked the idea of the PVC to have as an option for later use, but I'm open to filling it if I have to. Need to figure something out because it's holding up my project big time

Love the forums here and looking forwarding to contributing. Thanks everyone!

 

[cdherman]

Well, no one gave you advice, so I'll just tell you what I did. I shoved a wad of plastic bags down the hole, to plug it, then used some insulating foam to make a close to liquid tight seal, and then mixed quart of fiberglass resin/hardner and then shoved some glass fiber into the hole and poured the resin in and let it harden. This is in a setting where I knew we would never need to open it up.

The also make plugs like this one. This one would stick up, BUT, you could used a nut instead of the thumbscrew and cut off the threaded rod so that its all flush with your floor.

 

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[wwhitney]

That type of mechanically expanding rubber plug is also available in a flush variety. E.g. RealTite plugs or PROPLUS 301162. Those are just the first two options I turned up by searching, no particular recommendation.

Cheers, Wayne