What is a Window Well?

Window wells are prefabricated plastic or concrete units fixed to the wall in front of the basement window. A grate sits on top; at the bottom, the rainwater that falls through the grate has to go somewhere. There are two solutions:

• Soakaway: the bottom of the well is open or filled with gravel, and the water seeps into the ground. That works on permeable soil. On clay or with high groundwater, the water stays put.
• Drain with a connection: a drain in the floor of the well leads into the drainage system or the underground pipe to the sewer.

The second option has a catch that many people overlook: if the floor of the well is below the backflow level and the drain is connected to the sewer, sewage can rise into the well from below during sewer backflow. That is why the German federal flood protection guide explicitly calls for backflow protection in the drain of flood-resistant window wells.

The German insurance association GDV explicitly lists window wells as one of the ways water gets into a building during heavy rain. These are the typical cases:

• Surface water runs over the rim: the top edge is too low, or the ground slopes towards the house.
• The drain is blocked: leaves, soil and small animals clog it. The well then fills up just from the rain falling through the grate.
• Backflow through the drain: sewage rises into the well from below when the drain is connected below the backflow level without protection.
• Overflow from the roof: an overflowing gutter above the well pours extra water in.
• Leaky joints: water pushes through between the well and the wall, or at the window itself, as soon as it stands in the well.

Once the well is full, the basement window usually doesn’t hold for long. Ordinary windows aren’t built for this; even flood-resistant windows have a maximum water height, according to the federal flood protection guide. A single blocked window well can be enough to flood a basement room.

• Drain test: pour a bucket of water into the well. If it’s empty after a short while, the drain is clear. If a puddle stays, it needs cleaning.
• Height: measure how far the top edge sits above the ground, and watch where rainwater flows on the lawn, terrace or driveway.
• Drain connection: ask or check the plans to see where the drain leads. If it goes into the sewer and the well sits below street level, backflow protection is a must-discuss.
• Joint and window: cracks between well and wall, brittle window seals, damp patches inside below the window.
• Roof: is there a gutter or downpipe directly above the well?

Good times are after the leaves fall in autumn and before the thunderstorm season. You need a professional if the drain goes into the sewer unprotected, the well has sunk, or the wall below the window gets damp.

Drainbee doesn’t hang in the window well. The probe measures the level in a pump sump or lifting station. If water runs through the window onto the basement floor and doesn’t find its way into the sump, Drainbee sees none of it. A water leak detector under the window is the right choice for that.

It’s different if your basement has a pump sump that the room or the drainage drains into. The BBK recommends such a sump with a submersible pump at the lowest point. If the level there rises faster in heavy rain than the pump can lower it, or the power goes out, Drainbee reports it by push notification or call-style alarm in the app.