How Do We Seal an Opening in Our Foundation Wall?
Q: "We upgraded the electrical service in our home, and the new wiring comes into the house through an opening in the foundation wall that was originally used to pipe cistern water into the house. But now when it rains, water seeps through the opening and drips on the service panel in the basement. What should we do?"
We upgraded the electrical service in our 1887 Victorian about 10 years ago. The new wiring comes into the house through an opening in the foundation wall that was originally used to pipe cistern water into the house. But now when it rains, water seeps through the opening and drips on the service panel in the basement, where the circuit breakers are. My son temporarily solved the problem by leaning a piece of plywood against the house to deflect water. I was hoping you might have a better-looking solution.
— Ann, North St. Paul, MN
Noel Williams replies: First of all, don't mess with the panel if it's wet inside; electricity and water are a dangerous combination. It's not a problem to be ignored, either. Water in the service panel means corrosion, which can prevent the breakers from tripping when circuits overheat. Your only choice is to call a licensed electrician. However, you should be able to make the necessary leak-stopping repairs yourself.
First, find out how the water is coming in. If it's seeping in on the inside of the plastic conduit that comes through the foundation wall, the problem might be something as simple as a loose access cover on the pull box; that's the fitting on the exterior of the house where the outside wires make a 90-degree turn and go inside. All you need to do in this case is tighten the screws that hold the cover in place.
But if water is coming in around the outside of the conduit, which is more likely, head to the basement and look for gaps between the conduit and the concrete. For any gap that's less than 3/8 inch or so, stuff foam backer rod into the crack, then seal it with a tripolymer sealant. This is a very flexible sealant and sticks to all sorts of building materials, even when they're slightly damp.
For bigger gaps, hand-pack both inside and out with hydraulic cement. Wear rubber gloves to protect your skin against chemical burns, and work quickly because hydraulic cement sets up in minutes.
While you're at it, do what you can to make sure water doesn't collect near the pull box. Sloping the ground around it away from the house should help a lot. And finally, make sure your gutters aren't dumping water into this vicinity.
Noel Williams is a former electrical contractor and building inspector and the author of several books on electrical codes. He lives in Herriman, Utah.