Sizing tools: gravity pipes, flows, attenuation, first flush

Diameter, gradient or flow capacity of a partially full PALADEX gravity pipe, with velocity, filling ratio and self-cleansing checks.

What would you like to calculate Diameter Gradient Flow capacity Filling ratio

Sewer type

Design flow

l/s

Gradient

‰

Minimum flow (optional)

l/s

Optional: the low (e.g. dry-weather) flow, to check self-cleansing. For foul sewers usually 20–50% of the average flow.

Formula

Operational roughness kb

Allows for manholes, joints and slime layer: under DWA-A 110 it applies to any pipe material.

Peak stormwater runoff using the rational method and the local rainfall depth–duration curve.

Catchment surfaces

m²

Rainfall curve coefficient a (mm/hⁿ)

Rainfall curve exponent n

h = a·tⁿ for the chosen return period: in Italy the a and n values are published by ARPA and the River Basin Authorities for each rain gauge or grid cell. For times of concentration under one hour use the a, n pair of the sub-hourly branch.

Time of concentration (min)

min

Time of entry into the network (5–15 min) plus time of flow in the sewers. Minimum 5 minutes.

Average and peak domestic foul water flow for any population.

Storage volume required for hydraulic invariance, using the rainfall-only method and the minimum volumes set in Lombardy (Italy).

Volume and flow rate of the first-flush runoff to be separated and treated.