Approved Document H (drainage)

Calculators that use it

• Drain fall calculator

  Example: Drop: 300 mm over the run (1 in 40, 2.50%)

• Soakaway calculator

  Example: Storage depth 1.00 m (0.74 m³ of storage for the critical storm)

• Guttering and downpipe calculator

  Example: Rainwater flow: 1.26 L/s from 60.0 m² of effective roof

• Percolation test calculator

  Example: Infiltration rate f = 3.55 × 10⁻⁵ m/s