Graf 380050 Notice D'installation Et D'entretien page 24

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5. Installation
5.4.1 Positioning on a slope, embankment etc.
If the tank is installed in immediate proximity (less
than 5 m) to a slope, mound or embankment, a
statically calculated supporting wall must be con-
structed to bear the pressure of the soil. The wall
must exceed the tank dimensions by at least 500
mm in all directions and must be at least 1000 mm
away from the tank.
5.4.2 Groundwater and cohesive (non-water-permeable) soils (e.g. clay)
Sufficient drainage of the groundwater / seeping
water should be ensured if groundwater occurs
occasionally and if the soils are cohesive and
water-impermeable (e. g. clay) so that the tanks
never stand in more groundwater than is stated in
the table. If necessary, the drainage pipe must
end in a vertical DN 300 pipe in which a submers-
ible pressure pump is fitted to pump out the ex-
cess water. The pump should be checked regu-
larly. If the tanks are expected to be immersed
deeper, sufficient drainage should always be
ensured.
Covering heights with ground water
>800<1500 mm.
Tank size
all tank sizes
We generally recommend laying a drainage pipe
because the ground water level may rise unex-
Submersion depth
1275 mm
pectedly during long periods of rain.
5.4.3 Installation next to driven-on surfaces
If the underground tanks are installed next to
roadways used by heavy vehicles of more than
40 t, the minimum distance from these surfaces
must be at least the depth of the trench.
5.4.4 Connecting multiple tanks
Two or more tanks are connected via welded DN
250 pipe connections (twice the nominal diameter
of the intake pipe). The pipe connections should
be positioned as far down the tank as possible.
Ensure that the distance between the under-
ground tanks is at least 600 mm.
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