Water and sewerage charges for businesses

Understand your water and wastewater bills


Your business may receive a number of bills relating to water and wastewater charges.

Water bills

Factors that affect your water bill charges include:

  • size/diameter of the incoming water supply pipe
  • year - unit costs are reviewed annually
  • the demand placed on the service either through usage or wastage

Metered charges

For customers with a meter, the bill will show the charge based on the volume of water used. A standing charge will be added based on the size of your water supply pipe. When you receive a bill, check the meter serial number to make sure you are being billed for your meter. Measured charges.

Unmeasured charges

Bills may be based on 'estimated', 'actual' or 'read' meter readings. NI Water charge for all water supplied and recorded through the meter, whether used or lost through leakage. Leakage, allowances and costs.

Sewerage charges may appear on your trade effluent bill rather than your mains water bill.

For customers without a meter, the bill will show the charge based on the rateable value of the property and a fixed fee standing charge. Unmeasured charges.

Sewerage bills

Sewerage (domestic wastewater) charges appear on either your water bill or your trade effluent bill and can be based on:

  • incoming water less non-return to sewer allowance
  • incoming water less measured trade effluent volume, less non-return to sewer allowance
  • the rateable value of your premises

If your bill is higher than normal because of a leak, you may be eligible to apply for an adjustment of the sewerage charges on your bill if the leaked water did not return to the sewer. Leakage responsibilities, allowances and costs.

Trade effluent bills

Trade effluent volume may be metered or based on the calculation of water use, less non-return to sewer allowances. These allowances include losses, eg from non-recovered steam, evaporative losses from cooling towers and water used as a product ingredient.

To calculate the amount discharged as domestic sewerage, you may be asked to provide data.

Trade effluent charges are based on the Mogden Formula that relates cost to the volume and strength of the trade effluent discharged. The formula takes into account the facilities at the sewage treatment works that treats your trade effluent.