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2. Installation
General instructions for installation of backwater valves
According to DIN EN 12056 it is not allowed to connect all drainage fix-
tures from a building (including those located above the backwater level
– ground level) through a backwater valve. The reason being that when
the backwater flap is in the closed position due to backwater / flooding
no wastewater will be able to flow through the backwater valve meaning
that the building’s own wastewater will flood out of the lowest drainage
fixture connected (normally in the basement) to the backwater valve.
Incorrect installation of a backwater valve
Correct installation of a backwater valve
DIN EN 12056 specifically states that only drainage fixtures below the
backwater level may be connected to a backwater valve. All drainage
fixtures above the backwater level should be drained through a sepa-
rate pipe directly into the sewer (not through the backwater valve). This
means that the home / building must be equipped with separate drai-
nage pipes. A building’s wastewater from above the backwater level
(above ground level) can drain freely into the sewer at all times. During
backwater the higher head / pressure of wastewater above the back-
water level will force its way into the surcharged sewer and will not flood
the basement / lower levels. Rainwater drainage pipes must not be
connected to a backwater valve.
Wrong
Right:
Backwater valve
Sewer
Backwater valve
Sewer
Backwater
level
Backwater
level
