I need to run a hot and cold water supply line to an outside structure 13' away through my basement block wall. This is in the Northeast US, where the frost line is 42" and the penetration will therefore be that much below grade.

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I plan to use 3/4" PEX-A pipe wrapped in foam self-seal pipe insulation and running through FLEX-Drain corrugated pipe.

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The whole assembly will penetrate the houses basement wall below the frost line on one end and will come up through a concrete slab foundation (to be poured) on the other. The flex-drain pipe would essentially act as the sleeve through both the house wall and the concrete slab foundation. I have a few questions that perhaps someone could comment on:

  1. Is FLEX-Drain a good idea to use for this application? It seems a little flimsy and I'm a bit worried it may eventually crack while regular PVC pipe seems like overkill.

  2. Would FLEX-Drain be a good sleeve or would I need to use a larger diameter PVC pipe as the sleeve and run the flex-drain through it?

  3. Regardless of sleeve options - what is the best thing to use to seal/waterproof between the sleeve and block wall penetration? What about between the pex and the sleeve?

Thank you!

  • 2
    "Regular PVC" is the standard an is fairly inexpensive. Why is it overkill?
    – isherwood
    Nov 15, 2018 at 17:31
  • @isherwood I'm sorry - overkill may have been the wrong word. What I meant was running it the full length (13' away from foundation and 4' up through slab). My other concern is it would require a 90 degree elbow and if I ever needed to replace the pex - not sure how easy it would be to pull it out with the elbow in place.
    – Yev
    Nov 15, 2018 at 17:36
  • 1
    Have you thought about heating the water in the target structure instead of piping it there? You don't mention how long the run is, but if it's long, it may take a while to get warm water.
    – Gary Bak
    Nov 15, 2018 at 17:50
  • @GaryBak I have - the run will be ~17' total (13' horizontal, 4' vertical) so there's no need for heating water at the structure. Taking a while to get warm water is not an issue.
    – Yev
    Nov 15, 2018 at 17:53
  • 2
    @Yev - you can buy sweep elbows for PVC that make a gradual bend rather than a sharp corner. Since it's just a protective sleeve, you could even use schedule 80 conduit, even bigger sweeps are available for that. Nov 15, 2018 at 18:38

2 Answers 2


Uponor Ecoflex is your best bet here. https://www.uponor-usa.com/~/media/uponor/sidebar%20brochures/pips_pg_h460_0113a.ashx?version=012120130317. You will need, as others mentioned, a schedule 80 sweep to sleeve the concrete penetration. Use expanding spray foam to seal the open end of the pvc. Using the foam insulation below grade....will get saturated with water over time and no longer will have any insulating value. Your goal here is to protect the pex from getting torn by rock, etc, below grade. I'd skip the insulation and go deeper and sleeve it all in PVC, or use the Ecoflex, which at the end of the day, will cost you less then the extra time and materials with your original option. Make sure you pressure test before closing things up, and as long you pass that and aren't burying any fittings, you'll never need to replace it.

  • I like the idea of the insulation, I have never used that product but it looks worth an up vote.+
    – Ed Beal
    Mar 19, 2019 at 20:31

4" pvc waste pipe is cheap and strong. You should definitely insulate the pipes so the heat in the hot line doesn't transfer to the cold pipe. 4"pipe will allow for the installation. Where the pipe breaches the foundation wall you need to seal it with hydrolic cement and even a rubberized membrane over that. Don't use spray foam. Make a good clean hole if possible with a core bit. Excavate a good foot or two under the hole and laod the area with 3/4 cush grave to allow water to drop away from the wall. There is almost no such thing as overkill when dealing with concrete and excavation. If you do use 4"pipe use two 45 degree elbows with a foot or so section in between to make your bend.

  • Waste pipe would be a good alternate but I would use sweeps much easier to pull through and the cost might be less.
    – Ed Beal
    Mar 19, 2019 at 20:29

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