Water & Wastewater Industry Glossary (A–Z): Valves, Pipelines, and Treatment Terms Explained

Water and wastewater projects are full of abbreviations, standards, and specification language that can confuse even experienced teams when moving between sites, councils, contractors, and OEMs. This Water & Wastewater Industry Glossary is designed as a practical reference for engineers, operators, and procurement teams — explaining the everyday terms you’ll see on datasheets, drawings, tenders, and commissioning documents.

Use it to sanity-check specifications, align terminology across stakeholders, and make valve selection and package quoting faster and more accurate.

A–Z GLOSSARY (WATER & WASTEWATER)

A – Actuator
A device used to operate a valve automatically. In water sites this is commonly electric (remote control) or pneumatic (fast acting), often paired with position feedback for SCADA.

A – Air Valve (Air Release / Air Vacuum Valve)
A valve installed on pipelines to release trapped air and admit air during draining or negative pressure events. Correct sizing is critical because air pockets can cause flow restriction, noise, and surge.

B – Backflow Prevention
Methods and devices used to stop contaminated water flowing back into a clean supply. Includes check valves, reduced pressure zone devices, and air gaps. Backflow protection is fundamental for potable water safety.

B – Butterfly Valve
A compact quarter-turn valve used widely on large diameters. Often chosen for water distribution due to low weight, simple operation, and cost efficiency.

C – Chamber
An access structure (often concrete) housing valves, meters, and fittings below ground. Good chamber design improves maintenance access and reduces failure risk.

C – Check Valve (Non-Return Valve / NRV)
A valve that allows flow in one direction and closes automatically to prevent reverse flow. Used to protect pumps, prevent contamination pathways, and reduce system instability.

C – CIP (Clean-In-Place)
More common in hygienic sectors, but can appear in water facilities for certain cleaning regimes. Refers to cleaning internal pipework without dismantling.

D – Ductile Iron (DI)
A common material for water valves and fittings due to strength and toughness. Often supplied with protective coatings to combat corrosion in buried or wet environments.

D – Double Eccentric / Double Offset
A butterfly valve geometry that reduces seat wear during operation. Used where tighter shut-off or higher duty cycles are needed.

E – Effluent
Treated wastewater leaving a plant. Requirements vary by discharge consent and receiving environment.

E – Erosion
Wear caused by abrasive solids, grit, or high velocity flow. Erosion can damage seats and trim, leading to leakage and reduced control.

F – Flow Control
The ability to regulate flow rate through a system. Achieved using control valves, pressure reducing valves, or variable speed pump control.

F – Flange (Flanged Connection)
A bolted pipe connection used for reliable sealing and ease of maintenance. Common standards include PN flanges. Correct gasket selection and bolt torque matter.

G – Gate Valve (Sluice Valve)
A linear isolation valve used to fully open or fully close flow. Favoured in distribution networks for low headloss when fully open.

H – Headloss (Pressure Loss)
The reduction in pressure as water moves through pipework, valves, bends, and fittings. Valve choice impacts headloss and therefore pumping costs.

I – Isolation Valve
Any valve used to shut off a section of a system for maintenance. Isolation points are essential for safe plant operation and minimising downtime.

J – Jetting
A cleaning method used in sewers to clear debris using high-pressure water jets. Often referenced in maintenance planning.

K – Knife Gate Valve
A valve designed to cut through slurries and solids. Common in wastewater, sludge handling, and screenings applications where standard valves may clog.

L – Level Control
Controlling tank, wet well, or process levels. Achieved using sensors and modulating valves, or by pump control with valve protection.

M – Modulating Valve
A valve that can position anywhere between open and closed to regulate flow or pressure. Requires an actuator and often a positioner.

M – Meter (Flow Meter)
Measures flow rate (and sometimes total volume). Common types include electromagnetic (mag), ultrasonic, and turbine meters. Accurate metering supports compliance and leak detection.

N – Nominal Bore (NB / DN)
The nominal internal size of pipework and valves, used for standardisation. DN is metric sizing used across water infrastructure.

O – Odour Control
Processes to manage hydrogen sulphide and other odours in sewage networks and treatment plants. Can influence material selection and corrosion risk.

P – PN Rating
A pressure rating system used in Europe (e.g., PN10, PN16). It indicates the valve/flange pressure class at a reference temperature, not a guarantee at all temperatures.

P – Potable Water
Water suitable for human consumption. Components in contact with potable water often need WRAS approval or equivalent compliance to protect water quality.

P – Pressure Reducing Valve (PRV)
A valve that reduces downstream pressure to a set level. Used to protect assets, stabilise networks, and reduce leakage levels in distribution.

Q – Quarter-Turn Valve
Valves operated by a 90-degree turn (e.g., ball and butterfly). Favoured for quick operation and compatibility with compact actuators.

R – Rising Stem / Non-Rising Stem
Stem movement style in gate valves. Rising stem provides visible position indication; non-rising stem is common in buried installations with limited space.

S – SCADA
Supervisory Control and Data Acquisition. The remote monitoring and control layer used by water companies and plants. Valves with actuators, limit switches, and feedback integrate into SCADA for status and alarms.

S – Sludge
Concentrated solids removed during wastewater treatment. Sludge handling requires valves designed for abrasion, clogging resistance, and chemical exposure.

S – Surge (Water Hammer)
A pressure spike caused by sudden changes in flow, such as pump start/stop or fast valve closure. Managing surge is critical to prevent pipe bursts and equipment damage.

T – Throttling
Partially closing a valve to restrict flow. Some valves are suitable for throttling; others will wear rapidly if used this way.

T – Treatment Works (WWTW / STW)
Wastewater treatment works / sewage treatment works. A site where sewage is processed through screening, settlement, biological treatment, and final discharge handling.

U – Ultrasonic Metering
A non-intrusive flow measurement method used in clean water and some wastewater applications. Useful where minimal pressure loss and low maintenance are priorities.

V – Valve Seat
The sealing surface that prevents leakage when a valve is closed. Seat materials must match the media and duty cycle; poor seat choice is a common cause of leakage.

W – WRAS
Water Regulations Advisory Scheme approval. Indicates products meet requirements for use with potable water systems in the UK, helping ensure materials don’t contaminate water.

W – Wet Well
A collection sump where wastewater accumulates before pumping. Wet well level control and anti-backflow protection are key design considerations.

X – Xylem / OEM References
You may see OEM names in specifications indicating preferred suppliers or “or equivalent” requirements. Always match performance, ratings, and compliance rather than brand alone.

Y – Y-Strainer
A filter fitting used to protect downstream equipment (PRVs, meters, control valves) from debris. Regular cleaning is critical to avoid pressure drop and control problems.

Z – Zone Management
Dividing distribution networks into zones (often DMAs) to control pressure, monitor flow, and reduce leakage. Valves and PRVs are core tools in zone management.

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