Water Consumption / Discharge Calculator

Calculates water supply cost, estimated sewerage/wastewater discharge volume and cost, and overall water balance, using the standard "Return-to-Sewer" billing method used by most water utilities.

Water Consumption

Water Consumption (m³) From your water meter reading for the billing/reporting period.

Water Supply Rate ($ / m³)

Discharge / Sewerage

Return-to-Sewer Allowance (%) Most water utilities assume 90–95% of supplied water returns to sewer as wastewater by default.

Sewerage / Wastewater Rate ($ / m³)

Trade Effluent Surcharge ($ / m³, optional) Additional charge for non-domestic-strength discharge (e.g., high COD/BOD), commonly assessed via a Mogden-style formula. Leave at 0 if not applicable.

Optional — Water Intensity

Number of Employees (optional)

Units Produced (optional)

Water Supply Cost

Sewerage / Discharge Cost

Total Water Bill

0 m³

Est. Discharge Volume

0 m³

Non-Return (Lost/In-Product)

Formula Reference

Water Supply Cost = Consumption × Water Rate
Estimated Discharge Volume = Consumption × (Return-to-Sewer % ÷ 100)
Non-Return Volume = Consumption − Discharge Volume (evaporation, in-product water, cooling tower losses, etc.)
Sewerage Cost = Discharge Volume × Sewerage Rate + Discharge Volume × Trade Effluent Surcharge
Total Water Bill = Water Supply Cost + Sewerage Cost

About the Return-to-Sewer Allowance

Most UK water and sewerage wholesalers apply a default Return-to-Sewer (RTS) assumption of 90–95% to metered sewerage billing, recognizing that not all supplied water reaches the sewer (evaporation from cooling towers, water incorporated into product, off-site tankering, etc.). Businesses that lose significantly more water than this default can apply to their water retailer for a non-return-to-sewer allowance, usually verified by sub-metering. This assumption is a billing convention, not a fixed physical constant — always check your own water/wastewater contract for the actual percentage applied.

Return-to-sewer billing conventions vary by country, utility, and site-specific agreement — the 90–95% default reflects common UK water industry practice and should be adjusted to match your actual water/wastewater supplier's tariff. Trade effluent strength charges (e.g., the Mogden Formula, which factors in COD/BOD/suspended solids) are only approximated here as a flat surcharge; contact your wastewater provider for an exact trade effluent consent calculation. For customized calculators tailored to your organization, please contact Impact Tech Solutions.