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Northern Ireland Water (NI Water) supplies water and sewerage services to Northern Ireland businesses. It also sets the charges based on usage or property value.

Types of water charges for businesses

Metered water charges for businesses

If your business has a water meter, you pay a fixed standing charge based on your supply pipe size plus a variable charge depending on the actual water used. For more information, see .

Unmetered water charges for businesses

If you do not have a water meter, charges are based on your property's rateable value plus a standing charge. For more information, see .

Domestic allowance for eligible businesses

Businesses that pay business rates may qualify for a domestic allowance of 100m³ of water every six months. This allowance reduces your metered water bill but cannot be carried over to the next billing period. To apply for the domestic allowance, and provide proof of your rateable status. 

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Assessed water charges for non-metered properties

If installing a water meter isn't possible, you can request an assessed charge. This includes a standing charge and a variable charge calculated from the water-using appliances on your property. Domestic allowance may also apply here if you pay business rates.

Large user tariff

Large water users may qualify for a reduced tariff reflecting lower service costs. Contact NI Water to see if your business qualifies. For more information, see .

Regulation of water charges

The oversees water and sewerage charges in Northern Ireland. It sets limits on price increases, monitors service quality, and ensures fair pricing for all customers.

Using non-mains water sources

If your business uses water from wells, boreholes, or reservoirs, you must notify NI Water. You may need permission from the Northern Ireland Environment Agency to abstract or impound water. This helps ensure your sewerage charges are calculated correctly. See .

How to reduce your water and sewerage costs

Lowering your water use can reduce your bills. You can reduce water use by:

• monitoring your water meter regularly
• identifying and fixing leaks promptly
• installing water-efficient appliances and fixtures
• considering water reuse or alternative sources like rainwater

For further tips and ideas on how to reduce water use in your business, see reduce your water, sewerage, and effluent costs and .

Businesses connected to the public sewer system must pay sewerage charges. These charges cover the cost of wastewater and drainage services. There are two parts to sewerage charges:

• a standing charge is a fixed fee based on your water supply pipe size
• a variable charge is based on the volume of wastewater discharged

Measured sewerage charges

If your business has a water meter, sewerage charges are calculated based on the water you use, minus an allowance for water that does not return to the sewer (standard non-return allowance is 5%). The standing charge depends on the size of your supply pipe.

Non-return to sewer allowance

The standard non-return allowance is 5%, but businesses can apply for a higher allowance if more water is used but not returned to the sewer.

For more information, see .

Domestic allowance for eligible businesses

If your business pays business rates, you may qualify for a domestic allowance of 95m³ every six months. This allowance reduces the volume of water charged for sewerage. To apply for the domestic allowance, and provide proof of your rateable status.

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Unmeasured sewerage charges

If you do not have a water meter, sewerage charges are based on your property’s rateable value with a fixed standing charge. There is a cap on the total charges to protect customers from excessive bills. For more information, see .

Assessed sewerage charges

Where installing a meter is not practical or too costly, NI Water offers assessed charges. These include a standing charge, and a variable charge calculated from the water-using appliances on your property. Domestic allowances may also apply if you pay business rates.

How to reduce sewerage costs

Reducing your water consumption lowers both water and sewerage bills. Simple steps include fixing leaks, using water-efficient equipment, and monitoring your meter regularly. See reduce your water, sewerage, and effluent costs and .

Discharging to surface water drains

If your business discharges anything other than clean water into surface water drains or watercourses, check if you need permission from the Northern Ireland Environment Agency to prevent water pollution. For more information, see preventing water pollution.

If your business discharges contaminated wastewater, known as trade effluent, into the public sewer system, you must get consent from Northern Ireland Water (NI Water). Trade effluent is any liquid waste produced by industrial or commercial processes that is different from normal domestic sewage, which is charged separately.

What is trade effluent?

Trade effluent includes wastewater contaminated with substances such as:

• fats, oils, and greases
• chemicals
• detergents
• heavy metals
• solids
• food waste

How are trade effluent charges calculated?

NI Water charges businesses on both the volume and strength of the trade effluent before it enters the sewer system. This ensures fair pricing that reflects the cost of treating different types of wastewater. For more information, see .

As a business, you may receive several bills related to water supply and wastewater disposal. Knowing how these charges are calculated helps you manage your costs effectively.

What affects your water bill?

Your water bill depends on several factors, including:

• size of your water supply pipe - the diameter affects standing charges
• annual unit costs – charges are reviewed every year
• water usage or wastage – the amount of water your business consumes or loses

Metered water charges

If your business has a water meter, your bill will include:

• a variable charge based on the actual volume of water used
• a standing charge based on the size of your supply pipe

Always check your bill to ensure it matches your meter’s serial number and actual readings. Northern Ireland Water (NI Water) charges for all water recorded on the meter, including losses from leaks. For more information, see .

For more information, see .

Unmeasured water charges

If your business does not have a water meter, charges are based on:

• the rateable value of your property
• a fixed standing charge

Bills may be based on estimated or actual meter readings, where applicable. For more information, see .

Sewerage charges

Sewerage (wastewater) charges may appear on either your water bill or your trade effluent bill. These charges are calculated based on:

• incoming water volume minus a non-return to sewer allowance (standard 5%)
• incoming water minus measured trade effluent volume and non-return to sewer allowance
• the rateable value of your premises if unmetered

If your bill is unusually high due to a leak and the leaked water did not enter the sewer system, you may be eligible to apply for a sewerage charge adjustment.

Trade effluent charges

Trade effluent is wastewater from your business processes that is not domestic sewerage. Charges for trade effluent are based on:

• the volume of effluent discharged (metered or calculated)
• adjustments for non-return to sewer allowances, such as steam losses, evaporation, or water used in products
• the strength of the effluent, calculated using the Mogden Formula, which considers treatment costs at sewage works

You may be asked to provide data to help calculate the domestic sewage portion of your discharge. For more information, see .

Key tips for managing your water and wastewater bills

• Regularly check meter readings and bills for accuracy.
• Report leaks promptly to avoid unnecessary charges.
• Understand your allowances and apply for any you qualify for.
• if you have questions about your charges or need to apply for adjustments.

Reducing the amount of water your business uses is one of the most effective ways to lower your water, sewerage, and trade effluent bills. Since Northern Ireland Water (NI Water) charges both for supplying water and treating wastewater, cutting water use helps save money and reduces your environmental impact.

Practical tips to reduce water consumption

To manage water use efficiently, make sure to:

• check your water supply pipe to ensure it matches your business needs
• monitor your water meter readings and bills regularly to spot unusual usage early
• inspect pipes for leaks, especially during cold weather when pipes are more vulnerable
• invest in water-efficient equipment to reduce water consumption

For more practical steps, see water efficiency: ten top tips.

Water-saving measures by business type

Offices

Office-based businesses can install water-saving devices such as push taps, spray taps, cistern displacement blocks, and sensor-controlled flush systems. For more information, see save water at commercial premises.

Factories

Industrial businesses might reuse process water or greywater from cleaning and washing. They can also explore alternative water sources like rainwater harvesting or other non-mains supplies. For more information, see save water at industrial premises.

Reducing sewerage and trade effluent costs

Wastewater treatment and trade effluent charges can be significantly higher than water supply costs. To reduce these expenses:

• Minimise the volume of wastewater your business produces.
• Lower the strength or pollutant levels in your trade effluent by improving processes or using less harmful substances.
• Reuse wastewater where possible to reduce discharge volumes.