After having replaced ~30' of 4" cast iron w PVC, I'm left with two holes in the cinderblock foundation. The holes are the height of 1 block and about 1/2 the width of a block. These leaves a pretty significant hole around the pipe.

I'm inclined to think I'll need to build a crazy custom form to go around the pipes and be able to access the hole as I work.

But I'm also thinking there has to be a better way.

Both holes have already been backfilled inside from the top. So all work needs to be done on the exterior.

Also note the rubber boot between the PVC and the cast Iron? I've found mixed opinions on the need to surround that with poured concrete. In truth this work (the butt joins not the wall repair) will likely be revisited several years in the future.

Here are pics of both sewer lines. Also note - both lines now have clean-outs and boots. The pic on the second one was taken before that was completed.

Sewer Line 1 Sewer Line 2

1 Answer 1


I would fill the wall around the pipe with hydraulic cement to get a water-tight seal.

Both the PVC and the rubber boot need UV protection. Those should be buried under at least 6 inches of dirt (that was the recommendation of the inspector when I had to do a similar repair).

  • When filling the hole with any kind of cement, would't I need some sort of form to keep it from falling out of the hole until it sets?
    – dwcouch
    Commented Oct 27, 2014 at 18:26
  • Hydraulic cement cures in less than 10 minutes. You can wear gloves and pack it in by hand and use a trowel to smooth it out. I would recommend doing it in several small batches since it doesn't have a long working time. Commented Oct 27, 2014 at 19:07
  • 1
    Ask This Old House has a great video demonstrating the use of hydraulic cement to seal around a PVC pipe. I'll try and find it later.
    – longneck
    Commented Oct 27, 2014 at 19:13

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