I need help determining what is the proper approach to sealing an incoming water line main through a concrete block wall.

The main water line is coming in about 2 feet below ground level. The space between the PVC pipe conduit and the water line leaked water during a heavy storm last night.

My initial thought is to pump silicone sealant into the void space. Any advice?

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(Update: I went with a combination of silicon sealant within the void of the PVC pipe, then Flex Tape around the exterior opening.)

  • 1
    it depends on the space size, if it is 1/4 inch or less use silicone.
    – Traveler
    Commented Jul 14, 2022 at 1:44
  • do you have dimple board protecting your foundation wall? Commented Jul 14, 2022 at 1:49
  • It's a 1 1/2 inch PVC pipe conduit, and a 1 inch water line pipe.
    – Mason T.
    Commented Jul 14, 2022 at 1:51
  • @FreshCodemonger Not dimpleboard, there is a type of waterproof lining though on the concrete wall.
    – Mason T.
    Commented Jul 14, 2022 at 1:53
  • I should note that the waterproofing I found on the water line was a type of rubberized tape that had been wrapped several times around the opening.
    – Mason T.
    Commented Jul 14, 2022 at 1:54

3 Answers 3


When I did my water line passing into my house through a concrete wall I left a square knockout in the form work. After stripping the forms and running the pipe through we filled the void with concrete. After it was filled with concrete the concrete wall was sprayed with damp proofing. After it was damp proofed I installed some rigid insulation and dimple board. Once the dimple board was installed we blue skinned the dimple board to the pipe where it went through the dimple board.

In your case, I'd probably dig a pit where it enters at least 12" lower than the entry point. Take some landscape fabric and make a wall around the pit. Blueskin your water service to the foundation wall. Fill the pit with gravel.

If it rains the ground water will have to come up at least the 12" for it to want to go into the garage. If it isn't too much work then dig the pit down to your perimeter drain where the water will be taken away ( assumes you have perimeter drain ).

Instead of silicone maybe try an epoxy putty.

This one is NSF and suitable for exterior use.


  • Sounds like your approach is similar to the existing waterproofing technique. Would applying a sealant within the PVC pipe then wrapping the opening work as well?
    – Mason T.
    Commented Jul 14, 2022 at 4:35
  • Sure applying some silicone between the pipe and the concrete isn't going to hurt. Commented Jul 14, 2022 at 6:12
  • My plumber used some kind of two part epoxy stick when trying to seal an inlet pipe into a concrete sump well. It reduced the leak but might have worked if we had clean / dry conditions. Commented Jul 14, 2022 at 6:36

I would use a very simple method.

Expanding Foam, that will seal the water leak hole.

Apply on the outside and on the inside of the concrete wall

Use the product that says UV resistant.


Source: Lowes.com

If for some reason you have to remove the pipe in the future, that can be done easily.

  • The foam would be below ground, is that acceptable?
    – Mason T.
    Commented Jul 14, 2022 at 4:35
  • 5
    Spray foam tends to shrink as it ages and cracks. If you do any passive house air sealing you know to avoid spray foam as an air barrier. If it can't block the air over a long time span it isn't blocking water. Commented Jul 14, 2022 at 6:13
  • 2
    If it's below ground, why does he need UV resistance?
    – FreeMan
    Commented Jul 14, 2022 at 18:47

The other answers here are seriously flawed in one way or another. You'll see why by reading this:


Sealing of sleeves can be accomplished several ways, although many practices which are thought to be satisfactory are actually very detrimental to the copper tube.

One such practice that should be avoided is the sealing of the space between the tube and sleeve with silicon caulk. Many silicon caulking materials outgas ammonia and/or methanol during their curing process. The outgassing of ammonia, within the sleeve, can lead to stress corrosion cracking of the copper tube, and eventual failure.

Another often employed practice that should be avoided is the sealing of the sleeve with hydraulic cement. Though no adverse reaction with the copper tube will occur, the fact that the tube is held very rigid at the location of the hydraulic cement may contribute to stress fracturing of the tube at that point. Stress fracturing is caused by overworking the tube at that point through motion from thermal expansion/contraction, movement of the backfill material by freezing and thawing, or settling of the soil or structure around the sleeve and tube by improper compaction of the backfill.

Two inexpensive and easily installed ways to properly seal sleeves, water-tight can be accomplished using Fernco TM elastomeric clamps (Figures 1 and 2 above) and electrician's duct seal (Figure 3). Both of these allow the tube to expand and contract and move within the sleeve and still maintain the water-tight seal.

It only takes one serious flaw in an approach to risk failure and water infiltration.

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