A flow test introduces a measured volume of water into a drainage system to confirm that the installation is hydraulically capable of carrying its design flow without surcharge or backing up. Engineers run the test from a known source at a defined rate, observing downstream chambers, fittings and outfalls. The method is particularly relevant for large commercial schemes, SuDS designs and high-rise residential developments across Greater London where calculated flows under BS EN 752 and Building Regulations Part H must be demonstrated in practice. Findings inform sign-off of new drainage, support adoption applications under Sewers for Adoption with Thames Water, and provide reassurance for clients and insurers. The work is carried out by qualified engineers using calibrated flow meters and a clear written record forms part of project handover.
Flow test (drainage capacity)
Test introducing measured flow into a drain to confirm hydraulic capacity meets design.
