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What is a Drainage System?

A drainage system is an underground dewatering system that collects seepage and perched water around a building and channels it away in a controlled manner. It consists of perforated pipes laid in a gravel bed that direct water to a pump sump or outfall. In Germany it is planned to DIN 4095. Drainage relieves the basement walls of seepage water, but it does not lower a high groundwater table. Against groundwater that presses permanently, only a watertight construction helps.

By Jonas Derissen, Managing Director of Drainbee GmbH 3 min read Updated

At a glance

standard for drainage
DIN 4095
probe measuring range
0–1 m
visual check per year
1×
layers: fleece, gravel, pipe
3

How does it work?

The drainage system is typically installed around the basement walls during construction. Perforated drainage pipes collect water accumulating in the soil and channel it by natural gradient to a collection point — the pump sump. From there, the water is pumped away by a submersible pump.

The system consists of several layers: a filter fleece prevents soil particles from washing in, a gravel layer ensures good water permeability, and the actual drainage pipes with slots or holes collect the water.

Drainage systems require regular maintenance. Ochre deposits (iron oxide), root intrusion, or silting can clog the pipes and drastically reduce drainage performance. Professional flushing every few years is recommended.

Where the water may go is set by your municipality's drainage bylaws. As a rule, drainage must not be connected to foul or combined sewers. If it runs into a stormwater sewer, backflow protection makes sense.

What does this have to do with Drainbee?

A drainage system works out of sight — and that is exactly what makes it risky. When the drainage clogs or the pump at the end of the system fails, the water level in the pump sump rises. Drainbee monitors this water level around the clock and detects drainage problems early.

What the shaft mainly reveals is the inflow. If noticeably less water arrives after comparable rain than it used to, while the basement walls get damp, the drainage may be clogged. If the pump runs much more often, more water is arriving, for example because the groundwater is rising. You can see both in the app's rain and inflow history.

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Frequently asked questions

How often does a drainage system need maintenance?
Look at the pump sump and the inspection and flushing shafts at least once a year: is there silt in them, or does hardly any water arrive after rain? How often the system needs flushing depends on the soil. With iron-rich water the pipes clog with ochre much faster, and professional flushing is needed more often.
Can a drainage system be retrofitted?
Yes, retrofitting drainage is possible but requires excavation around the building. That makes it one of the more expensive measures, and it often pays to renew the exterior waterproofing at the same time. Get several quotes and first clarify whether seepage water is really the problem, or groundwater, which drainage won't help against.
How do I know if my drainage system is no longer working?
Signs include damp basement walls and a musty smell, especially if at the same time less water reaches the pump sump after rain than it used to. Then the water is probably backing up against the wall instead of draining away. A monitoring system like Drainbee shows you in the inflow history whether anything is changing.

Sources

  1. DIN Media: DIN 4095-1:2026-06 – Baugrund – Einwirkungen auf erdberührte Bauteile durch Wasser im Baugrund und Dränung zum Schutz der Bauteile – Teil 1 (opens in a new tab)
  2. DIN Media: DIN 18533-1:2026-06 – Abdichtung von erdberührten Bauteilen – Teil 1 (opens in a new tab)
  3. Stadt Regen: Merkblatt über die richtige Rückstausicherung (opens in a new tab)

Related terms

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