0

Preface

The proper way to seal any kind of water leakage in a concrete wall is from the outside. That is not always practical, as in this case. This question is about alternatives to solve the problem, and alternatives do exist. Solutions such as interior surface coatings, and apparently hydraulic cement, are not effective. However, some other solutions are available, and I'll mention a couple that I know about below.

Background

About a year ago, I posted the question How to seal a pipe pass-through in a basement wall. The gist of that question was two pipes passing through a poured concrete foundation wall (one an iron sleeve, one a PVC sleeve). Foam had been used to seal the gaps between the sleeves and the wall. After 15 years, ground water had started to leak in around the sleeves.

My fix included hydraulic cement (recommended on how-to sites as the proper solution). However, the hydraulic cement appears to be water permeable. So I'm back for phase 2.

Previous Solution

The typical contractor solution at construction is to fill around the pipes with spray foam. The foam is not rated as water submersible or even waterproof (probably why the old foam failed), so replacing it wasn't a solution. I ended up cleaning out all the old foam, cleaning and sealing the surface of the iron sleeve with neoprene-based adhesive, and then packing the voids with hydraulic cement. The cement has adhered well, but after 10 months, water is seeping through it. Apparently, the stuff is porous.

Current Condition

A picture of the current condition (click on it for a larger image):

enter image description here

Below the iron sleeve on the right (the original issue), the hydraulic cement is darker from the moisture and you can see some efflorescence. The bigger problem is the PVC pipe on the left, which I didn't think would be a problem to seal. The hydraulic cement around that pipe is visibly wet, and enough water gets through to drip.

Constraints

  • This can't be sealed from outside. The exterior of that wall is not accessible without significant destruction and reconstruction, which would be cost-prohibitive.
  • The walls are 8" thick poured concrete, so common solutions for tapping cinderblock walls aren't applicable.
  • Relieving the water pressure from the inside may not be practical (busting up the basement floor, tunneling under the footer, and creating a drain channel to an existing sump pump). The house is located next to a community water catchment field, so the water table is high. A sump pump would need to drain ground water from several acres to stay ahead of the water table, and the discharge goes back into that same field.

So this is a candidate for an alternate solution designed for when an exterior fix isn't practical.

Potential Solutions

I am aware of several possible solutions:

  • Injecting sealant into the wall: This is commonly used for structural cracks and leakage problems. Epoxy is injected into cracks for structural repairs, Polyurethane is injected into cracks and pipe pass-throughs to seal water leaks. These are injected the full depth of the wall and are supposedly stronger than the concrete, itself.

    In my case, I would need to break up the hydraulic cement and then seal the gaps with an injected polyurethane system (professionally done high-pressure injection or a DIY kit like this; short video of the DIY process here). There are a few brands of such DIY kits. The kits aren't cheap ($100 for each pass-through), and professional injection is several times that cost.

  • Control and direct the water flow rather than trying to seal it out: This is commonly done with cinderblock walls. The cores are tapped so water has an easy path to a collection system and goes to a sump pump for discharge. Sometimes the interior walls are then lined with a waterproof membrane to control humidity.

    In my case, the basic idea would be to drill a channel in the hydraulic cement directly below each pipe so water has an easy path to drain and is not under pressure. Connect these to tubing that runs down to a nearby floor drain.

Question

Has anyone had experience with these (or other) solutions and can share how successful it was long term?

4
  • What makes this task difficult, if not impossible, is the requirement, "This can't be sealed from outside." Successful methods of sealing require application from the side with pressure, i.e., ground water infiltrating from outside. You might think of a way to do this from outside. Jun 11 at 2:17
  • @DrMoishePippik, That is the right way to do it, but there isn't a way to access the exterior of that wall without massive destruction and reconstruction. The cost would be prohibitive.
    – fixer1234
    Jun 11 at 2:30
  • There are epoxy compounds that can be injected under pressure to seal cracks and leaks in poured concrete walls from the inside. I had that done (or the builder did) to a newly constructed home. This was done by a 3rd party, not the builder, but at the builder's expense. That held up fine, no leaks in the 20 years we lived in the home.
    – SteveSh
    Jun 11 at 11:39
  • @SteveSh, now that you mention it, I recall that technique. It's worth investigating. Thanks.
    – fixer1234
    Jun 11 at 15:58
2

I fixed the problem successfully, and cheaply. I'll post the solution for other people in a similar situation.

As mentioned in the question, the problem needed to be fixed on the inside. Injecting sealant into the wall would have been expensive. I'm not aware of another practical way to seal concrete from the inside against water pressure. So I solved it by letting the water in and controlling it.

If you let the water drain through the wall, it never builds up pressure under normal conditions. There will be some water in contact with the concrete inside the wall, so there may eventually be some efflorescence. However, a small, occasional trickle of water won't produce the amount of efflorescence as water under pressure sitting against the concrete for long periods of time, and it will be localized to a small area.

Details of the solution

I drilled several inches into the concrete directly under the pass-through sleeve. A drain tube was sealed in the hole. The seal needs to be water-tight, but there is no strain on the tube and the water isn't under pressure, so you only need to prevent capillary action from allowing water around the seal.

To ensure that water has a path into the drain tube, leave a tiny gap between the tube/sealant and the back of the hole rather than pushing the tube and sealant tight against the back of the hole.

Ensure that the hole is located where the water has a good path to it. I verified that water was draining from the hole using a temporary fix, then waited for a dry spell to make the permanent fix.

If it is a water table issue, the water drainage may not be while it's raining. It may take up to several days for surface water to raise the water table and seep to your house. If water appears while it's raining or soon after, look for a problem like clogged rain gutters, downspouts dumping water next to your house, or bad grading, and fix that, which is likely to solve the problem.

Sealant

The initial solution was to use butyl rubber as the sealant. That worked. The concrete needs to be dry, free of dust, and warmed with a heat gun. Force the rubber deep into the hole around the drain tube. It sticks well to the concrete as long as the concrete is dry. Once it sticks, the seal will be waterproof. Warming the rubber makes it soft and sticky, and helps to establish a good seal.

I probably could have left that alone. The rubber firmed up at room temperature and made a good, water-tight seal, but I wasn't sure whether the seal would last forever, and was concerned that the rubber might eventually sag. So I pulled out the plug, scraped the hole clean of rubber, and replaced it with something more permanent.

You could use epoxy, or something like a moldable silicone putty like Sugru. I opted for plastic that is moldable when warmed in hot water. There are many brands of this material, so I won't promote a particular product. They are similar to nylon at room temperature, but melt into a putty when warmed above about 140°F. In the soft state, it bonds like hot melt glue with a number of materials, including concrete, metal, and some plastics (i.e., the wall and the drain tube), and doesn't appreciably expand or contract with temperature, at least in the ranges used.

The concrete was warmed with a heat gun to minimize rapid cooling and hardening at the seal surface, and a heat gun kept the plastic warm while forming and sealing the plug. Pipe cleaners were stuffed into the drain tube during installation to ensure it didn't get plugged with sealant.

Water control

Plastic tubing runs from the drain tube to a nearby floor drain. If you don't have a floor drain, you can use a condensate pump to send the water to a sink or outside.

Results

The solution works well. There is no leakage or signs of damp concrete at the wall, and water drains out. It required just a few dollars worth of material. I expect the fix to last "forever", but should it ever fail, it will be easy enough to remove and replace.

1

The problem is that it can only be sealed form the other side.

On this side the water pressure will tend to blister or spall any sealing compound you apply, applied on the other side the pressure will tend to push it against the wall.

If the conduits are sealed into the wall and you can keep the other side dry (perhaps using a de-watering pump) it may be possible to clean them out and get a seal in there and then back the seal with cement or sand-filled epoxy once it has cured.

on the other hand it may be possible to dill a hole through the wall and inject a large quantity of some sealing compound and have that block the leak

4
  • 100% agree with sealing this from outside. Why do you say you can't do that? A good sealing compound to use on the outside is Bentonite clay which is available in many locations. Check your local Vermeer or Ditch Witch dealer. Just dig a hole past the bottom of the pipe and dump enough Bentonite, dry, into the hole. Then backfill.
    – jwh20
    Jun 11 at 12:47
  • @jwh20, I also agree with sealing this from the outside, but digging a hole implies digging through soil, which isn't the case. See comment on the question.
    – fixer1234
    Jun 11 at 15:54
  • @fixer1234 All I see is the statement "exterior of that wall without massive destruction and reconstruction". I'm not clear why you cannot explain what is in the way.
    – jwh20
    Jun 11 at 16:02
  • @jwh20, it's always good to question the assumptions when those can stand in the way of a proper fix. In this case, the cost and practicality of accessing the exterior of that wall is something I'm familiar with. Getting into a discussion of that is really a different question, and I don't want to sidetrack this thread when there are potential nondestructive solutions that can be accomplished from the inside, like injecting a sealant into the wall, or letting the water in and routing it to a floor drain.
    – fixer1234
    Jun 11 at 16:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.