Ever heard your sump pump running, and running, and running — but the water level in the basin never seems to drop? Your pump might be airlocked — and that puts your home in jeopardy, as water continues to trickle into the basin with no place to go. It will also risk burning out your pump.
The solution? A weep hole — a tiny hole drilled into the discharge pipe between the pump and the check valve — prevents air lock by allowing air trapped in the system to escape. If your sump pump system doesn’t have a weep hole, you should create one to extend the life of your pump and protect your home from flooding.
What Is an Air Lock?
Sump pump systems are designed to turn on when water in the basin reaches a certain depth, then stop pumping once the float switch indicates there’s no more water to pump. That means that for a brief time, before the system realizes the water’s gone and the pump shuts off, the pump will draw air up into the discharge pipe.
If there’s no way for that air to escape, it will remain trapped in the discharge pipe, between the pump and the check valve. The next time the pump turns on, the air bubble will be “locked” inside the system and compressed by the action of the pump trying to move water through the pipe. The bubble can’t escape through the discharge pipe, and the system will be locked. Though the pump will continue to run — because the float switch is telling it there’s still water to be removed — no water will actually leave the basin.
That creates a dangerous situation for the pump, which could burn out, and for your basement, which will flood as water continues to flow into the basin.
A weep hole — also called a relief hole or vent hole — gives that air bubble somewhere to go. Some sump pumps have built-in weep holes, or the plumber who originally installed your system might have drilled one for you. If your system doesn’t already have a weep hole, that’s OK — installing one is quick and easy.
How to Install a Weep Hole
Installing a weep hole is a simple matter of drilling a small hole in the discharge pipe, using an ordinary household drill. Weep hole size, placement, and angle are key, so before drilling, consult the pump’s owner’s manual for any recommendations.
This video from R.C. Worst & Co. Inc. is an excellent explainer on weep holes and how and why to install one
What Size Should a Weep Hole Be?
A weep hole should be about 3/16” in diameter. This is small enough to not compromise the pump’s power, but large enough that the hole won’t get clogged easily by bits of dirt, gravel, or debris.
Note that the hole could still get clogged — so make inspecting and clearing your weep hole part of your regular sump pump cleaning regimen.
Weep Hole Placement
The weep hole should be made down in the sump basin, between the check valve and the pump itself, and below the water line for your system — the depth at which the float switch triggers the pump to turn on. Placing the weep hole below the water line ensures that the air can escape, but also that any water that sprays from the weep hole doesn’t escape the sump basin and hose down your basement walls or floor.
Don’t drill all the way through both sides of the pipe. The weep hole should be a single hole through just one wall of the discharge pipe.
Weep Hole Angle
Drill the weep hole at a 45-degree angle so that it aims down into the basin, rather than up and out toward the ceiling. This ensures that when water sprays from the weep hole — and that’s going to happen, as you can see in this video — it lands in the sump pump basin instead of all over your basement or crawl space.
Installation Steps
- Determine the best height for the weep hole by filling your sump pump basin with water until the pump turns on. As soon as the pump starts, mark the water level with a marker or pencil.
- Allow the pump to empty the basin. Once the basin is empty, unplug your sump pump, disconnect it from the discharge line, and remove it from the basin before drilling the weep hole. This gives you room to work, ensuring that you can get the proper angle and placement for the hole.
- Using a 3/16” bit, drill the weep hole, making sure to position the hole between the check valve and the spot where the pump connects to the discharge pipe, and below the water level line you drew on the discharge pipe.
- Reposition the pump in the basin, reconnect the discharge pipe to the pump, and plug in the pump.
- Test the system by pouring water into the basin until the pump starts running. Water should spray from the new weep hole into the basin and the pump should empty the basin as normal.