Venting, relief drain and emergency overflow

When it rains, the air in the sewer must give way to water. So there must be vent points in the sewer system. New homes usually have a down pipe for this purpose. Old homes lack this pipe. In practice, this means that air escapes from the sewer system through the downspout. If there is no down pipe and the downspout is disconnected from the sewer system, the air looks for another way to escape. This often results in bubbling toilets and sinks.

You can avoid this by constructing an alternative vent pipe. In addition, it is helpful to construct a relief drain near the older stormwater drain. You need to make sure that the rainwater can drain away even when the infiltration facility is completely full during an extremely heavy rainstorm. This is called the emergency overflow.

Description operation vent, relief drain and emergency overflow

• 
  The rainwater (A) coming from the gutter runs through the downspout either above ground or below ground to the infiltration facility.
• If wastewater or rainwater cannot drain quickly enough due to a blockage, the water can drain into the garden via a relief manhole or scrubber (B).
• If the infiltration facility is completely full and the water cannot flow superficially to a lower point, then the stormwater (C) can drain through the emergency overflow (relief manhole or scrub pit) through the sewer system (C).
• The air (D) from the sewer can now escape through a second pipe on the wall connected to the sewer.