Leaks at Pipe and Conduit Penetrations: A Guide for Mechanical and Electrical Rooms

It usually starts as a dark ring on the concrete around a pipe. Then there’s a drip, then a small puddle on the floor of the mechanical room. Sometimes it’s a conduit, and the water is turning up in a room full of panels and switchgear.

A pipe penetration leak in a concrete wall is a common below-grade leak in commercial and strata buildings, and it shouldn’t wait. These rooms hold the equipment that keeps the building running, and water next to it is a problem that tends to get worse as the wet season goes on. Here’s why penetrations leak, where to look, and how they’re sealed from the inside. When you’re ready for a site look, see our concrete leak and penetration repair page.

Why pipe and conduit penetrations leak

Every pipe, sleeve or conduit that passes through a concrete wall creates a joint between two different materials: metal or plastic on one side, concrete on the other.

Those materials don’t behave the same way. They expand and contract differently as temperatures change. Pipes vibrate with pumps and flow. Buildings settle. Over time, the grout, sealant or concrete packed around the penetration shrinks, cracks or pulls away, and a gap opens up. It may be too small to see, but it’s big enough for water.

On a below-grade wall, groundwater is pressing on the outside. When it rises in November and stays high through the Lower Mainland’s wet season, it pushes into the weakest spot it can find, and the gap around a penetration is often the first one.

Where a pipe penetration leak in a concrete wall usually starts

Around a sleeve or core-drilled hole

Many pipes pass through a sleeve cast into the wall, or through a hole cored after the concrete was poured. Either way, there are two joints: one between the pipe and the sleeve or hole, and one between the sleeve and the concrete. Water can follow either. Cored holes in particular can leave a rough, uneven edge that was never fully sealed.

At abandoned or unused penetrations

Old lines get removed, services get rerouted, and the hole stays behind, sometimes with a cut-off pipe stub, sometimes plugged loosely with whatever was on hand. These are easy to forget and easy to miss on a walk-through, but they’re a direct path through the wall.

Conduit runs, where water can also travel inside the conduit

Electrical conduit is a special case. Water can come in around the outside of the conduit, where it meets the concrete, and it can also get inside the conduit itself and travel along it to a junction box or panel. That’s why a conduit leak through a foundation wall can show up well away from the wall.

Clusters of pipes through one opening

Where several pipes or conduits pass through a single opening, the packing between them is hard to do well. There are more joints, more movement and more places for water to get past.

Why it matters more in electrical and mechanical rooms

A wet patch in a storage room is a nuisance. An electrical room water leak is more serious, because of what’s in the room.

• Water near electrical equipment. Panels, switchgear, transformers and controls don’t belong near water. If any electrical equipment is wet, or water is near it, keep people away and have a qualified electrician assess it before anything else.
• Pumps and mechanical gear. Pumps, valves, boilers and controls often sit right beside the wall where services come in.
• Corrosion. Constant moisture rusts sleeves, pipe supports, conduit and fittings.
• Staining and damage to equipment pads. Water spreading across the floor stains and undermines the concrete pads that equipment sits on, and makes the room harder to keep clean and safe to work in.

Signs to look for

Walk your mechanical, electrical and service rooms during or after heavy rain and check every pipe and conduit that goes through an exterior or below-grade wall:

• A damp ring or tide mark on the concrete around the pipe or sleeve.
• White crusty deposits at the entry. That’s efflorescence, minerals left behind as water moves through; see our post on white mineral deposits at the pipe entry.
• Rust staining on the sleeve, pipe or supports.
• Drips that get worse in storms and slow down in dry weather.
• Water inside conduit or a junction box, or moisture at a panel. Treat this as an electrical issue first.
• Puddles on the floor directly below a penetration.

Sump pits have their own version of this problem; see our post on pipe entries into sump pits.

How pipe penetrations are sealed from the inside

On an existing building, the outside of the wall is usually buried. So we do pipe penetration waterproofing from the inside face of the wall, against the water pressure. That’s negative-side repair, and it can often avoid excavation.

The general sequence for sealing a pipe through a concrete wall:

1. Clean back to sound concrete. Old, failed packing, loose grout and sealant are removed from around the pipe or sleeve, and the opening is cut back to solid concrete so the repair has something sound to bond to.
2. Stop running water. If water is flowing, we stop it with Krystol Plug, a rapid-setting hydraulic cement made to stop active leaks.
3. Treat the joint. The joint around the penetration is packed and treated with Kryton crystalline materials, including Krystol T1, which reacts with moisture to seal the pores of the concrete itself.
4. Inject where the gap needs it. Where the gap’s size or movement calls for it, we use compatible injection.

We’d rather see a penetration while it’s leaking, because the running water shows exactly where the path is.

You may also hear about other approaches, such as mechanical or link-type seals fitted around the pipe, re-piping, exterior excavation or a new exterior membrane. Ask us whether any of them suits your building, and we’ll give you our view after a site look. Our leak repair for strata and commercial buildings page has more on how we work.

Coordinating the repair with your trades and building

Penetration repairs happen in rooms that are busy with services, so a little planning helps.

• Keep services running where possible. Many repairs can be done with the pipes in service. Where a line needs to be isolated, your mechanical or electrical trade should confirm that and handle it.
• Electrical first. If the leak involves conduit or is near electrical equipment, have your electrician check and make it safe before the repair starts.
• Arrange access. Mechanical and electrical rooms are often locked. Tell us who holds the keys and who needs to be on site.
• Clear space at the wall. Move stored items away from the penetrations so they can be reached.
• Photograph and date the leak. Record where it is, when it leaks and how it changes, for the strata or owner’s records. Our fall below-grade walk-through has a simple logging format.

Common questions

Why does water come in around a pipe through a concrete wall?

A pipe through a wall is a joint between two materials that move differently with temperature, vibration and settling. Over time the packing around the pipe shrinks or cracks and a gap opens. When groundwater rises in the wet season, it pushes against the outside of the wall and finds that gap before anything else.

Can a pipe penetration leak be sealed from the inside?

Often, yes. We clean the opening back to sound concrete, stop any running water and treat the joint with crystalline materials, with compatible injection where the gap needs it. It’s negative-side repair, so excavation can often be avoided. Every penetration is different, so ask us whether it suits your building after a site look.

Do the pipes have to be shut down for the repair?

It depends on the line. Many penetrations can be repaired with the pipe in service, but some situations call for isolating it. Your mechanical or electrical trade should make that call and handle any shutdown. We’ll plan the work with them once we’ve seen the penetration.

Is caulking or spray foam around the pipe enough?

Usually not on a below-grade wall. Caulk and foam tend to fail on a wet joint that moves with temperature and vibration, and once water is pushing from behind, it gets around them. They also hide the evidence of where the water was getting in. Have the source looked at and treated in the concrete instead.

What if water is coming out of a conduit?

Treat it as an electrical issue first. Keep people away from the equipment and call a qualified electrician to assess and make it safe. Once that’s done, the entry point where the conduit passes through the wall can be sealed, so water stops getting in at the source.

Book a free penetration leak inspection

If water is showing up around pipes or conduit in your mechanical or electrical room, call us while it’s leaking. We repair penetration leaks from the inside for strata councils, property managers and facility teams across Vancouver, Burnaby, Richmond, Surrey and the Fraser Valley. See our concrete leak and penetration repair and strata and commercial leak repair pages, then call (778) 686-2221 (Mon–Sat, 8:30 AM–5:00 PM) or book a free inspection.