Preliminary aids

Water engineering tools

These calculators and the Excel workbook are educational aids for discussion and first estimates. They are not certified designs. Confirm units, standards, losses, equipment data and site conditions before use.

Download Excel toolkit

Water demand
Pipe hydraulics
Pump energy
Reservoir storage
Solar assessment

On-page calculators

Hazen–Williams pipe hydraulics

Flow (L/s)Internal diameter (mm)Pipe length (m)Hazen–Williams C

Velocity 1.415 m/s · Friction headloss 6.42 m

Coagulant chemical dosing

Plant flow (MLD)Target dose (mg/L)Product purity (%)

Active chemical 250 kg/day · Commercial product 277.778 kg/day

Sedimentation and sand filter

Plant flow (MLD)Clarifier overflow rate (m³/m²/day)Filter rate (m³/m²/hour)

Clarifier surface 333.333 m² · Filter area 83.333 m²

Rainwater harvesting audit

Catchment area (m²)Annual rainfall (mm)Runoff coefficient (0–1)

Estimated annual runoff 48 m³/year

Hazen–Williams headloss uses the SI coefficient 10.67. Chemical dosing treats 1 mg/L at 1 MLD as 1 kg/day. Clarifier and filter areas use the entered flow and ideal rates. Rainwater yield is a gross annual figure, without storage, first-flush, evaporation or recharge losses.