What is Basement Drainage?

1. Drainage – perforated pipes in a gravel bed around the foundation collect seepage and stratum water before it builds up against the basement wall. Design and sizing are governed by DIN 4095; a new edition of Part 1 was published in June 2026.
2. Pump sump with submersible pump – the lowest point, where drainage and seepage water collect. A float switch starts the pump, which lifts the water through a pressure pipe.
3. Floor drain – takes in water in the basement, for example from the washing machine or floor cleaning.
4. Lifting station – pumps wastewater from toilets, showers or basins below the backflow level into the sewer. The requirements are set out in DIN EN 12056-4.
5. Backflow protection – stops water from the public sewer pushing back into the house.

The difference between pump sump and lifting station matters: the sump usually collects clean ground and seepage water, the lifting station handles wastewater with or without faeces.

In heavy rain the sewer can fill up so much that water in the connecting pipes rises to the backflow level – usually the top of the road at the connection point, unless the local drainage bylaw sets something else. Under DIN 1986-100, every drainage point below that level must be protected against backflow.

There are two ways to do this: a lifting station pumps the water through a backflow loop above the backflow level and keeps the basement usable even during backflow. A backflow stop (backflow valve) closes when the sewer backs up – but while it is closed, nothing drains out of the basement either. The Verbraucherzentrale points out that owners are liable for backflow damage themselves if they have not installed protection contrary to the municipal drainage bylaw.

Whether drainage water may go into the sewer is decided not by technology but by the drainage bylaw of your municipality. Connecting it to the foul sewer is often not allowed or only with a permit; alternatives are the stormwater sewer, infiltration or a watercourse. Ask the local wastewater utility when planning or converting.

Just as important: if the pump in the pump sump discharges into a sewer, the pressure pipe needs a loop above the backflow level. Otherwise sewer water can flow back through the pump line into the sump during backflow.

• Pump and inflow: flow rate and delivery head must match the largest expected amount of water and the height to the outlet. An undersized submersible pump loses the race in heavy rain.
• Sump volume and switching points: a shaft that is too small makes the pump start very often for short runs, which wears out the motor and the float switch.
• Check valve in the pressure pipe, so the pumped water does not run back.
• Power outage: no power, no pump. If you live in groundwater or in a dip, consider a second pump, a backup power solution or at least an alarm.
• Access: shaft, pump and backflow stop must be easy to reach and service.

For wastewater lifting stations, DIN EN 12056-4 sets fixed intervals for servicing by a qualified person: yearly in a single-family house, every six months in an apartment building, quarterly in commercial premises. According to the Verbraucherzentrale, lifting stations and backflow stops must be checked and serviced regularly – otherwise you risk your insurance cover if damage occurs.

What you can do yourself:

• Fill the pump sump with a bucket of water and check that the pump starts, empties the sump and switches off again.
• Remove sludge and sand from the shaft and keep the float free to move.
• Operate the backflow stop as the manufacturer specifies and check that it seals.
• Open the drainage inspection chambers; have silted pipes flushed.

If water enters the basement through backflow from the sewer or after heavy rain, standard residential building insurance does not pay. For that you need natural hazard insurance – according to the GDV, around 41% of residential buildings in Germany had no such cover at the end of 2025. A burst pipe inside the house, on the other hand, is pipe water damage (see pipe burst).

Keep the service records for the lifting station and backflow stop. After a loss, they are often your proof that you met your obligations.

Most components fail silently: a stuck float or a broken pump only shows itself when the water comes. Drainbee uses a pressure probe to measure the level in the pump sump or the lifting station shaft, records pump cycles and inflow, and alerts you through the app when a threshold is exceeded, the power fails or the Wi-Fi drops out.

Drainbee does not control the pump, and it only sees what happens in the monitored shaft. It cannot tell whether a backflow stop closes or whether water is standing on the basement floor – that is what servicing and water leak detectors are for.