Backflow blocker
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Backflow blocker

A backflow blocker prevents sewage water from flowing back up through basement drains during heavy rainfall.

A backflow blocker is a device with two valves. The valves serve as a gate which opens when sewage water runs out from the house, but which closes if sewage water is pressed into the house. A backflow blocker is normally placed as close as possible to the building to be protected against flooding.


There are three types of backflow blocker:

  • One which is built into a floor drain; 
  • another which can be fitted on pipes where two floor drains are coupled together; and, finally;
  • a third type, which can be used on toilet drain pipes


The third type of backflow blocker can be used if there is a toilet. In this type of backflow blocker, one of the two valves can be closed electrically. Furthermore, the backflow blocker must be equipped with an alarm device which signals when the backflow blocker is closed, so that you are warned not to flush the toilet.



Illustation: Teknologisk institut

Senest redigeret: 04-02-2014