4.
T
ANK
INS
TALLA
TION
Graf UK Ltd
6
TANK INSTALLATION
Trench
To ensure that sufficient space is available for working, the base area of the trench must exceed the dimensions of
the tank by 500mm on each side; the distance from solid constructions must be at least 1000mm.
The trench embankment must be designed so that slippage or collapse of the embankment wall is not to be
anticipated. The construction site must be horizontal and plane and must guarantee sufficient loadbearing capacity.
The depth of the trench must be dimensioned so that the max. earth coverage (see point 2 installation conditions)
above the tank is not exceeded. To use the system throughout the entire year, it is necessary to install the tank and
those parts of the system which conduct water in the frost-free area. The frost-free depth is usually approx. 600mm
to 800mm; precise information in this regard can be obtained from the responsible authority.
A layer of compacted, round-grain gravel (grain size 10 to 20mm, thickness approx. 150 - 200mm) is applied as the
foundation.
Slope, embankment, etc.
On installation of the tank in the immediate vicinity
(< 5m) of a slope, earthen mound or slope, a statically
calculated supporting wall must be erected to absorb
the soil pressure. The wall must exceed the dimensions
of the tank by at least 500mm in all directions, and
must be located at least 1000mm away from the tank.
Groundwater and cohesive (water-
impermeable) soils (e.g. clay soil)
If it is anticipated that the tanks will be immersed
deeper into the groundwater than is shown in the
adjacent figure, sufficient dissipation must be ensured.
(See table for max. immersion depth).
Dissipation of the drainage water (e.g. via an annular
drainage system) is recommended in the case of
cohesive, water-impermeable soils.
Installation adjacent to surfaces used by
vehicles
If the underground tanks are installed adjacent to
surfaces which are used by vehicles heavier than
passenger cars, the minimum distance away from
these surfaces is at least the depth of the trench.
4
Population Equivalent
5 PE
7 PE
9PE
Tank size
3750
4800 L
6500
Immersion depth
350mm
350mm
350mm
>800<1200
max.
350mm
