If surrounded in a geotextile,
the stored surface water gradually infiltrates back
into the surrounding soil. A BRE365 test is recommended
to establish infiltration rates. These would indicate
the storage volume required.
Naylor MetroCell Units
Geotextile - non woven wrap
Naylor clay, or plastic drainage pipes and
fittings
Silt Trap
Drainage Inspection Chamber
Overflow
For Individual Properties Approved Document H allows a volume to be calculated by the area to be drained, multiplied by 10mm for areas up to 25m2. Above this size BS EN7524:1998 uses a figure of 20mm multiplied by the area to calculate a storage volume.
MetroCell Calculations How many MetroCell units will I need?
To calculate the amount of MetroCell units required for any particular storage volume, carry out the following simple procedure:
Example Only: Storage Volume Required = 150m³
Divide by 0.95/void ration = 157.9m³
Multiply by 3 (MetroCells per m³) = 474 units required for this example
