Graf STABILUS 3.000L Mode D'emploi page 15

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5. Installation
ü: max. 1000 mm h: 150-200 mm
a = distance between ground level and highest groundwater level (widest point of tank) ≥ ü + d/2
ü = permissible earth cover heights: 1000 mm ≥ ü ≥ 250 mm
h = heights of ballast needed: h ≥ 100 mm + d/5 with very firm or tightly compacted ground, otherwise h ≥
100 mm + d/10
(2) With coarse-grained soils and if you expect the maximum groundwater level to be above the tank
base (in this case up to the widest point of the tank), the minimum soil cover [ü] is 250 mm.
5.3 Trench
To ensure that sufficient working space is available, the base area of the trench must exceed the tank
dimensions by 500 mm on all sides. The distance from fixed structures must be at least 1200 mm.
The embankment should be built in accordance with DIN 4124. The foundation must be horizontal and
even and must offer sufficient load-bearing capacity.
The trench must be deep enough that the maximum earth cover above the tank 1000 mm (see page 2
point 2 - Installation conditions) is not exceeded. For the system to be usable all year round, the tank and
water-carrying parts must be installed in a frost-free zone. The frost-free depth is usually around 800 mm;
for accurate information, please contact the responsible authority.
(1) To produce the bed ballast (thickness approx. 150-200 mm) and the tank surround, use round gravel
with a grain size of 4/ 16 according to DIN 4226-1. Other gradated gravel mixes may also be used if they
are covered by the 4/ 16 grain range (e.g. 4/ 8 mm).
(2) Coarse-grained soil (group 1 or 2 according to ATV work sheet 127) with appropriate properties (no
stones) may be used to fill the area outside the surround.
If the ground is non-load-bearing, a reinforced lean concrete slab approx. 100 mm thick must be made.
5.3.1 Groundwater and cohesive (non-water-permeable) soils
If tanks are installed in groundwater, the water may come up to no more than half the tank height (=600
mm). Soil cover ≥ 600 mm.
If the soils are cohesive and non-water-permeable, ensure sufficient drainage of the groundwater/ seep-
age water. If necessary, the drainage pipe must end in a vertical DN 300 pipe in which a submersible
pressure pump is fitted to pump out the excess water. The pump should be checked regularly.
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