Why your window well fills with water

A window well is supposed to be a drain, not a container. When it holds water after a storm, you are looking at a few inches of standing water pressed directly against a window frame that was never built to hold it back.

This is one of the most common calls we get in Edmonton, and it is also one of the cheapest problems to fix if you catch it before the water finds its way through.

How a window well is supposed to work

A properly built well has gravel at the bottom, and under that gravel a vertical drain that connects down to the weeping tile at your footing. Rain and melt land in the well, pass through the gravel, drop into the drain, and leave with the rest of your groundwater.

Nothing about that system is visible from the yard. Which is why most homeowners find out it stopped working the same week their basement carpet gets wet.

Five reasons Edmonton wells fill up

1. The vertical drain is plugged

Leaves, silt and shingle grit wash into the gravel year after year and pack the top of the drain solid. The well still looks fine. It just stopped draining. This is the single most common cause we find.

2. There was never a drain to begin with

Plenty of wells around the city are a steel liner pushed into clay with a few inches of rock in the bottom. In sandy soil that can work. In Edmonton clay it does not, because the clay under the gravel holds water instead of taking it.

3. The weeping tile it connects to has failed

A vertical drain is only as good as the pipe it empties into. If the original weeping tile at your footing is crushed, clogged or clay tile that has shifted, the well drain has nowhere to send water.

4. Grading sends the yard into the well

The ground should fall away from your house. On a lot that has settled, or where landscaping was added over the years, the slope reverses and the well becomes the low point of the yard. Now it is not just catching rain, it is catching the yard.

5. The downspout empties beside it

A single downspout can move hundreds of litres off a roof in one storm. If it discharges within a few feet of a well, that entire volume goes into a hole against your foundation.

How the water actually gets into the basement

Three routes, in order of how often we see them. Through the joint where the window frame meets the concrete, because that seal was designed to shed rain and not to resist a column of water. Through the gap where the well liner is fastened to the wall, which lets water run down the outside face of the foundation behind the liner. And through the wall itself, where the fasteners that hold the liner have punched into the concrete.

If your basement only leaks near a window, stop looking at the wall. The well is the problem.

What you can check yourself this week

Pour five gallons of water into the well slowly and watch it. If it drops away within a couple of minutes, your drain is working. If it sits there, it is not.

Then look at the gravel. If you see soil, roots or a layer of packed silt on top of the rock instead of clean stone, the drain below it is almost certainly choked.

Last, check where the nearest downspout lets out and whether the ground slopes toward the well or away from it. Both are free to fix.

What the repairs cost

Clearing and rebuilding the gravel and drain in an existing well is the low end, and it is usually the right first move. Installing a new vertical drain and tying it into working weeping tile costs more because it means excavating beside the well. If the weeping tile itself has failed, you are into exterior work, which runs $300 to $400 per linear foot in Edmonton.

A well cover helps once the drainage works. It does nothing on its own, because it stops rain and not groundwater or melt running along the ground.

What to do next

Do the five gallon test. It takes two minutes and it tells you which of the two situations you are in.

If the water sits, send us a photo of the well from directly above and one of the window from inside. We will tell you what we are seeing at no cost, and if it needs work you will get the number before we come out.

Related reading: why your basement only leaks during spring melt and what weeping tile replacement costs.

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