I'm planning to build a 10x8 shed that will house the pipework and electrical equipment for a new well I recently had drilled. I would like the shed to sit on a concrete slab just for the quality of life it provides. My well contractor suggested that I pour the slab first, leaving 1x1 holes roughly 1' in from the corners where I can run pipework through afterwards.

  • Once the slab is finished with the holes, does it compromise the integrity of slab if I were to dig out the dirt between the hole and the edge of the slab to run the pipes?
  • How best to fill/pack dirt back in after the pipes are put in place? Should I fill the holes with concrete, or just pack in gravel to be flush with the surface of the slab?

Rough drawing of what it'll be like: enter image description here

  • Run rope through the pipes befire burying and concreting.
    – Solar Mike
    Jun 1, 2019 at 5:51

2 Answers 2


You could use large Schedule 40 PVC as conduit for the pipes. You'd use large radius bends. Will the pipes be PEX or copper? I think soft copper could be fed through a large radius bend and I am sure PEX could be. This would make replacing piping much easier if you ever needed to replace the piping under the slab.

  • The pipe is going to be poly pipe, so it should be very easy to work with. There will also be an electrical conduit going to the wellhead. I suppose that doesn't need to be in the slab; it can run down the side of the building.
    – atanamir
    May 31, 2019 at 23:55
  • Could you be more specific in your term "poly" pipe? Jun 1, 2019 at 1:54
  • How large conduit are you thinking? 2" or bigger?
    – JPhi1618
    Jun 1, 2019 at 3:13
  • 250PSI rated polyethylene 1-1/4" CTS pipe
    – atanamir
    Jun 1, 2019 at 3:25
  • I am not familiar with the bending properties of 1-1/4" CTS pipe. I suppose normally it goes more or less straight from a water main to a meter in a box or can in the ground and is direct burial. Using PVC as a conduit might not be feasible. Jun 1, 2019 at 10:17

Yes, openings that large and so near the edges will compromise the slab's strength. It will be difficult to support the adjacent corners after excavation in a reliable way and they are much more likely to crack loose. I would install extra rebar or mesh through those areas to make the slab edge essentially self-supporting.

How you fill the openings later is totally up to you. I'd use washed rock if available, otherwise gravel.

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