FAQ

Welcome to our UK Water Utilities Glossary, a comprehensive A–Z guide to the terminology, acronyms, and technical language used across the water industry. Whether you’re a utility professional, consultant, regulator, developer, or simply looking to better understand the sector, this glossary provides clear and concise definitions of common water utility terms. From AMP, Ofwat, and WRMP to leakage, abstraction, wastewater treatment, and smart metering technologies such as AMR and AMI, you’ll find straightforward explanations to help you navigate the complex world of UK water and wastewater services.

A

Abstraction
The removal of water from rivers, reservoirs, lakes, or groundwater sources for public supply, industry, or agriculture.

Abstraction Incentive Mechanism (AIM)
An Ofwat incentive that encourages water companies to reduce abstraction from environmentally sensitive water sources.

Abstraction Licence
Permission granted by the Environment Agency allowing a company to take water from a natural source.

Active Leakage Control (ALC)
The process of proactively finding and repairing leaks in the water network.

ADD (Average Daily Demand)
The average volume of water supplied or consumed per day over a year. ADD is calculated by dividing total annual demand by the number of days in the year and is commonly used for long-term planning and forecasting.

ADPW (Average Day Peak Week Demand)
The average daily demand during the highest demand week of the year. ADPW is a key metric in water resource planning as it reflects sustained periods of elevated demand, typically occurring during warm, dry weather.

AMI (Advanced Metering Infrastructure)
A more advanced form of smart metering that allows two-way communication between water meters and utility systems. AMI supports near real-time consumption data, leak alerts, remote diagnostics, and customer usage insights.

AMP (Asset Management Period)
The five-year regulatory planning and investment cycle for UK water companies.

AMR (Automatic Meter Reading)
A technology that enables water meter readings to be collected remotely without requiring a meter reader to visit the property. AMR systems typically transmit consumption data via radio signals to utility systems, improving billing accuracy and operational efficiency.

Aquifer
An underground layer of rock or gravel that stores groundwater.

Aquifer Storage Recovery (ASR)
A process of storing water underground for future use.

Asset Health
A measure of the condition and reliability of infrastructure assets.

Asset Inventory (AI)
A record of utility assets, including condition, size, age, and replacement value.

Available Headroom (AH)
The difference between available water supply and forecast demand.

B

Baseline Demand Forecast
A forecast of future water demand based on current policies and trends.

Baseline Supply Forecast
The forecast of future water availability using existing infrastructure and licences.

Best Value Planning
A planning approach balancing cost, resilience, customer value, and environmental outcomes.

Biodiversity Net Gain (BNG)
An environmental requirement ensuring developments improve biodiversity overall.

Biosolids
Treated sewage sludge suitable for recycling, often used in agriculture.

Borehole
A deep shaft drilled into the ground to extract groundwater.

C

CAMS (Catchment Abstraction Management Strategy)
Environment Agency plans that manage water resources within a catchment.

CAPEX (Capital Expenditure)
Money spent on new infrastructure, assets, and major improvements.

Catchment
An area of land where rainfall drains into a common river, reservoir, or groundwater system.

Catchment Management
Activities undertaken to improve water quality and environmental performance at source.

CBA (Cost Benefit Analysis)
A method for comparing the costs and benefits of different investment options.

CCW (Consumer Council for Water)
The independent body representing water customers in England and Wales.

CHP (Combined Heat and Power)
Technology that produces electricity and heat simultaneously.

Climate Change Adaptation
Actions taken to prepare for future climate impacts.

Climate Change Mitigation
Actions taken to reduce greenhouse gas emissions.

Combined Sewer Overflow (CSO)
A structure allowing excess sewage and rainwater to discharge during heavy rainfall to prevent flooding.

Communication Pipe
The pipe connecting a water main to a property’s boundary.

Conjunctive Use
The coordinated use of surface water and groundwater resources.

Consumption
The volume of water used by customers.

Customer Side Leakage
Leaks occurring on private pipework after the utility’s responsibility ends.

D

Defra
Department for Environment, Food and Rural Affairs.

Deployable Output (DO)
The reliable amount of water available from a source or treatment works.

DG2
A performance measure relating to customers at risk of low water pressure.

DI (Distribution Input)
The amount of treated water entering the distribution network.

Distribution Main
A pipe that transports water to customers.

Distribution Losses (DL)
Water lost through leakage from mains, reservoirs, and associated infrastructure.

DMA (District Metered Area)
A defined network area where water flows are monitored to identify leakage.

D-MeX (Developer Services Measure of Experience)
An Ofwat metric measuring developer satisfaction.

DMUU (Decision Making Under Uncertainty)
A planning method used to assess future water resource risks.

DO (Deployable Output)
The reliable quantity of water that can be supplied under specified conditions.

DPC (Direct Procurement for Customers)
A process allowing third parties to deliver large infrastructure projects.

Drought Order
Government authorisation for exceptional drought measures.

Drought Permit
Environment Agency permission allowing temporary drought-related abstraction changes.

DWI (Drinking Water Inspectorate)
The regulator responsible for drinking water quality.

DWQ (Drinking Water Quality)
The safety and quality of public drinking water supplies.

DWF (Dry Weather Flow)
Wastewater flow measured during dry conditions.

DY (Dry Year)
A year where water resources are under significant pressure.

DYAA (Dry Year Annual Average Demand)
The average daily water demand expected during a dry year. This measure is used in Water Resources Management Plans (WRMPs) to assess the balance between water supply and demand under drought conditions.

DYCP (Dry Year Critical Period Demand)
The highest demand expected during the most critical period of a dry year, usually during prolonged hot and dry weather. DYCP is a key planning metric used to test the resilience of water supply systems under stress conditions.

E

EA (Environment Agency)
The environmental regulator for England.

EBSD (Economics of Balancing Supply and Demand)
An approach used to compare supply and demand-side solutions.

Economic Level of Leakage (ELL)
The point where the cost of reducing leakage exceeds the value of water saved.

Effluent
Treated wastewater discharged back to the environment (read more here).

Environmental Flow Indicator (EFI)
A flow threshold used to assess environmental impacts of abstraction.

Environmental Performance Assessment (EPA)
The Environment Agency’s performance ranking system for water companies.

ERI (Environmental Risk Index)
A measure of risk from drinking water quality failures.

F

Final Effluent
Fully treated wastewater discharged from a treatment works.

Flood and Coastal Risk Management (FCRM)
Management of flooding and coastal erosion risks.

G

Groundwater
Water stored beneath the Earth’s surface in aquifers.

Guaranteed Standards Scheme (GSS)
Standards requiring compensation when service levels are not met.

H

Hands Off Flow (HOF)
A minimum river flow below which abstraction must stop.

Habitats Regulations Assessment (HRA)
Assessment of impacts on protected habitats and species.

I

I&I (Infiltration and Inflow)
Groundwater or rainwater entering wastewater networks.

INNS (Invasive Non-Native Species)
Species that may damage ecosystems or infrastructure.

Integrated Water Resources Management (IWRM)
A holistic approach to managing water resources.

Interruption to Supply
A temporary loss of water service.

L

Leakage
Water lost from the distribution network before reaching customers.

LPD (Litres Per Person Per Day)
The average amount of water used by an individual each day. LPD is widely used to measure household water consumption and assess the effectiveness of water efficiency programmes.

M

MDD (Maximum Daily Demand)
The highest volume of water demanded in a single day during a defined period, usually a year. MDD is used by water companies to assess network capacity, treatment works performance, and infrastructure resilience during peak demand events.

Managed Aquifer Recharge (MAR)
The deliberate recharge of groundwater supplies.

MCA (Multi-Criteria Analysis)
A method for comparing options against multiple objectives.

Megalitre (Ml)
One million litres of water.

Meter Optant
A customer who chooses to have a water meter installed.

Minimum Residual Flow (MRF)
The minimum flow required in a river after abstraction.

MOEO-RDM (Multi-Objective Robust Decision Making)
An advanced planning approach used in regional water resource planning.

MOSL (Market Operator Services Limited)
Operator of England’s non-household retail water market.

N

Natural Capital
Environmental resources that provide benefits to society.

Natural Capital Assessment (NCA)
Assessment of environmental assets and ecosystem services.

Net Zero
Achieving a balance between greenhouse gas emissions and removals (read more here).

Non-Revenue Water (NRW)
Water supplied but not billed because of leaks, theft, or metering errors.

Nitrate Vulnerable Zone (NVZ)
An area designated as being at risk from nitrate pollution.

O

ODI (Outcome Delivery Incentive)
Financial rewards or penalties linked to company performance.

Ofwat
The economic regulator of the water sector in England and Wales.

Operational Expenditure (OPEX)
Day-to-day operating costs.

P

PCC (Per Capita Consumption)
The average volume of water consumed per person per day, typically expressed in litres. PCC is one of the most important performance indicators used by UK water companies to monitor customer demand and support demand reduction strategies.

PDD (Peak Daily Demand)
The highest short-term daily demand observed or forecast within a specific period. PDD is often used interchangeably with MDD, although some organisations use it to describe exceptional peak demand events.

Performance Commitment (PC)
A target agreed between Ofwat and a water company.

Potable Water
Water that is safe to drink.

Pressure Reducing Valve (PRV)
A valve used to manage network pressure.

PR19 / PR24
Ofwat price reviews setting performance and investment requirements.

R

Raw Water
Untreated water from natural sources.

Reservoir
A storage facility for water.

Resilience
The ability to withstand and recover from disruptions.

Rising Main
A pressurised wastewater pipeline.

S

SCADA (Supervisory Control and Data Acquisition)
Systems used to remotely monitor and control assets.

SEA (Strategic Environmental Assessment)
An assessment of environmental impacts of plans and programmes.

Service Reservoir
A treated water storage facility.

Sewer Flooding
Escape of wastewater from the sewer system.

SPS (Sewage Pumping Station)
A facility used to pump wastewater.

Storm Overflow
A permitted discharge point operating during heavy rainfall.

T

TOTEX (Total Expenditure)
Combined capital and operational expenditure.

Treatment Works (TW)
A site where water or wastewater is treated.

Turbidity
A measure of water cloudiness.

U

Unaccounted-for Water
Water losses not reflected in customer billing.

Unplanned Outage
Treatment capacity unavailable because of equipment failure.

W

Water Framework Directive (WFD)
Legislation protecting and improving water environments.

Water Recycling Centre (WRC)
Modern term for a wastewater treatment works.

Water Resource Zone (WRZ)
An area where water resources and demand are managed together.

Water Resources Management Plan (WRMP)
A long-term plan showing how a company will balance supply and demand.

Water Stress
A situation where water demand exceeds available resources.

Water Treatment Works (WTW)
A facility treating raw water to drinking water standards.

Wastewater
Used water from homes, businesses, and industry.

Wastewater Treatment Works (WwTW)
A site treating sewage before discharge.

WINEP (Water Industry National Environment Programme)
Environmental improvement obligations placed on water companies.

Z

Zone Metering
The measurement of flows within defined sections of the water network to monitor performance and identify leakage.

 

Still Not Following Our Water Utilities Glossary?

If reading through this Water Utilities Glossary is giving you a headache, you’re not alone. From AMP and TOTEX to WRMPs, leakage targets, and regulatory frameworks, the industry is packed with terminology that can quickly become overwhelming. That’s exactly why we’re here.

We’ve created this Water Utilities Glossary to help demystify the language of the water industry, but understanding the terminology is only the beginning. Our job is to cut through the complexity, translate technical concepts into clear actions, and help organisations navigate an ever-changing regulatory and operational landscape.

So while we’ve documented the jargon here, you don’t need to become an expert in it. Leave that to us. We’ll handle the acronyms, regulations, and technical detail—so you can focus on the decisions that matter.