Plumbing Valves: The Complete Guide to Radiator Valves, Ball Valves, Gate Valves, Stopcocks and Isolators

Valves control, isolate, regulate, and direct water flow throughout a plumbing installation. Choosing the wrong type — a gate valve where a ball valve is needed, or a standard radiator valve where a TRV is required — creates problems that are expensive to rectify once the system is live. This guide covers every valve type in the Embrass Peerless range stocked at APM, with guidance on where each type is used and why.

Radiator Valves — Manual and Thermostatic

Every radiator requires two valves: a flow valve (which regulates or shuts off the water entering the radiator) and a lockshield valve (which balances the circuit and provides isolation for maintenance). For new domestic heating installations under current Building Regulations Part L, thermostatic radiator valves (TRVs) are required on all radiators except one — which must be in the same room as the room thermostat.

EDEN Thermostatic Radiator Valves (TRVs)

TRVs have a thermostatic head that responds to room temperature: as the room warms, the valve closes; as it cools, it opens. This gives room-by-room temperature control without additional wiring. All EDEN TRVs fit standard 15mm radiator tails with ½" or ¾" union nuts.

• EDEN TRV Angled White Head 15mm — £8.06 — angled body for side-entry radiator tails
• EDEN TRV Angled Chrome Head 15mm — £13.99
• EDEN TRV Straight White Head 15mm — £10.99 — straight body for bottom-entry tails
• EDEN TRV Straight Chrome Head 15mm — £12.99

Manual Radiator Valves (Flow Valves)

Where a TRV is not specified — radiator in the thermostat room, bathroom towel rails, electric heating — a manual radiator valve provides simple on/off isolation with a handwheel.

• Embrass Peerless 15mm Radiator Valve Angled ¾″ Nut — £4.89
• Embrass Peerless 15mm Radiator Valve Angled c/w Drain-Off ¾″ Nut — £7.33 — drain-off allows the radiator to be emptied without draining the full system
• Embrass Peerless 15mm Radiator Valve Reversible Angled ½″ Nut — £5.99
• Embrass Peerless 15mm Radiator Valve Reversible Straight ½″ Nut — £3.99

Towel Rail / Derwent Radiator Valve

• Embrass Peerless 15mm Derwent Towel Rail Radiator Valve Chrome Angled — £4.99 — slim-profile chrome valve designed for heated towel rails, where a conventional valve body would protrude awkwardly

Isolating Valves — Under Taps and Appliances

Isolating valves are fitted on the supply pipes to taps, toilets, dishwashers, and washing machines to allow individual appliances to be turned off and serviced without draining the system. The slot-head quarter-turn design requires a flathead screwdriver to operate — not hand-operable — which prevents accidental operation.

• Embrass Peerless Isolating Valve CP 15mm — £1.49 — standard service valve for basin, toilet, and kitchen tap supplies
• Embrass Peerless Isolating Valve CP 22mm — £3.38
• Embrass Peerless Isolating Valve Flat Faced CP 15mm × ½″ — £1.64 — flat-faced for direct connection to ½″ BSP tap tails
• Embrass Peerless Isolating Valve Flat Faced CP 15mm × ⅜″ — £2.64
• Embrass Peerless Isolating Valve Full Bore CP 15mm — £2.75 — full bore gives lower flow resistance; for supplies where flow rate is critical
• Embrass Peerless Isolation Valve Angle CP 15mm — £3.68 — angled body for tight spaces
• Embrass Peerless Service Valve Angle CP 15mm × ½″ — £1.37

Lever Ball Valves — Full Isolation and Zone Separation

Lever ball valves provide full-bore isolation with a quarter-turn handle — quicker to operate and easier to confirm open/closed status than screwdriver-slot isolators. Used for zone isolation on heating circuits, boiler service valves, and any point where a full-bore, hand-operable shutoff is needed. The lever position makes the valve state immediately visible.

Blue handle = cold water and general plumbing applications. Red handle = hot water and heating circuits. WRAS-approved versions required for potable water supplies.

Compression end (15mm–54mm)

• Embrass Peerless Lever Ball Valve Blue Handle 22mm — £5.90
• Embrass Peerless Lever Ball Valve Blue Handle 22mm WRAS — £8.67
• (same model, red handle) 22mm Red WRAS — £8.67
• Embrass Peerless Lever Ball Valve Blue Handle 28mm — £13.54
• Embrass Peerless Lever Ball Valve Blue Handle 28mm WRAS — £13.77
• Embrass Peerless Lever Ball Valve Red Handle 28mm — £13.26
• Embrass Peerless Lever Ball Valve Blue Handle 35mm WRAS — £35.23
• Embrass Peerless Lever Ball Valve Red Handle 35mm WRAS — £23.07
• Embrass Peerless Lever Ball Valve Blue Handle 42mm WRAS — £31.33
• Embrass Peerless Lever Ball Valve Blue Handle 54mm WRAS — £56.37

Female BSP threaded (¼ turn, full bore)

• Embrass Peerless Lever Ball Valve Female ½″ Blue Handle — £3.99
• Embrass Peerless Lever Ball Valve Female ½″ WRAS Blue — £5.06
• Embrass Peerless Lever Ball Valve Female ½″ Red Handle — £4.01
• Embrass Peerless Lever Ball Valve Female ¾″ Blue Handle — £6.70
• Embrass Peerless Lever Ball Valve Female ¾″ Red Handle — £6.93
• Embrass Peerless Lever Ball Valve Female 1″ Blue Handle — £10.96
• Embrass Peerless Lever Ball Valve Female 1″ Red Handle — £10.23

Butterfly handle / compact

• Embrass Peerless Butterfly Ball Valve Red Handle 22mm — £6.18 — compact butterfly-lever for installations where the standard lever would foul an adjacent fitting

Press-fit (Pegasus)

• 22mm Pegasus PressFit Lever Ball Valve — £8.96
• 35mm Pegasus PressFit Lever Ball Valve Red Handle — £20.22
• 42mm Pegasus PressFit Lever Ball Valve Red Handle — £35.67

Gate Valves — Full Bore, Low Resistance

Gate valves use a wedge-shaped gate that rises fully out of the flow path when open, giving zero flow restriction. They are slow to operate (multiple turns) but ideal for applications where the valve is normally open and the pressure drop across it must be minimal — pump suction lines, zone isolation on gravity heating systems, and CWSC ball valve bypass lines. Gate valves must be either fully open or fully closed; partially throttled, the gate vibrates and wears.

• Embrass Peerless 15mm Gate Valve Brass C×C — £3.99 — BS 5154, WRAS approved
• Embrass Peerless 22mm Gate Valve Brass C×C — £6.41
• Embrass Peerless 28mm Gate Valve Brass C×C — £11.29
• Embrass Peerless 22mm Pump Valve Gate Type — £6.90 — for boiler pump isolation; gate design minimises head loss across the pump
• Embrass Peerless 28mm Pump Valve Gate Type — £12.99

Check Valves (Non-Return Valves)

Check valves prevent reverse flow — critical on hot water cylinders to prevent cold back-siphonage, on boiler primary circuits where pump failure could cause gravity circulation in the wrong direction, and on combination boiler filling loops. DZR (dezincification-resistant) brass is required for hot water and heating applications.

• Embrass Peerless 15mm Single Check Valve Brass C×C — £1.80
• Embrass Peerless 22mm Single Check Valve Brass C×C — £3.99
• Embrass Peerless 15mm Double Check Valve DZR C×C — £3.09 — double check valves meet Water Regulations requirements for fluid category 3 backflow prevention (e.g. on filling loops, garden hose connections)
• Embrass Peerless 22mm Double Check Valve DZR — £6.21
• Embrass Peerless 28mm Double Check Valve DZR C×C — £9.47

Stopcocks — Mains and Service Isolation

Stopcocks are the standard valve for mains water service entries. Clockwise to close. Unlike a gate valve, the stopcock has a washer-and-seat mechanism that can be reground or re-washered in-situ without removing the body from the pipework — essential for service isolation valves that may not be operated for years.

• Embrass Peerless Trade Stopcock C×C Brass 15mm — £4.42
• Embrass Peerless Trade Stopcock C×C Brass 22mm — £7.26
• Embrass Peerless Stopcock Brass 28mm — £13.15

MDPE Stopcocks — Underground Mains

For terminating MDPE supply pipe at entry to the building, the MDPE stopcock transitions from polyethylene to copper in a single fitting.

• MDPE Brass Stopcock 15mm C×C × 20mm MDPE — £7.10
• MDPE Brass Stopcock 15mm C×C × 25mm MDPE — £6.34
• MDPE Trade Stopcock 15mm × 25mm MDPE — £6.97
• MDPE Brass Stopcock 20mm × 20mm MDPE — £11.95
• MDPE Brass Stopcock 22mm × 25mm MDPE — £10.82
• MDPE Brass Stopcock 25mm × 25mm MDPE — £16.33

Zone Valves and Gas Valves

Motorised Zone Valve

• Embrass Peerless 22mm 2-Way Motorised Zone Valve — £49.99 — electrically actuated, for use in mid-position 3-port or 2-zone heating controls. Connects to a Honeywell or Drayton zone control wiring centre. Essential for separating heating and hot water circuits where a 3-port valve is not used.

Gas Isolation Valves

• Embrass Peerless 15mm Lever Ball Valve Compression Yellow Handle — £9.99 — yellow handle denotes gas service. For LPG and natural gas isolation at appliance connections.
• Embrass Peerless 22mm Tesla Gas Isolating Valve c/w Test Nipple — £7.69 — test nipple allows gas tightness testing without disconnecting the fitting

Washing Machine Valves

• Embrass Peerless 15mm × ¾″ Self-Cutting Washing Machine Valve — £6.99 — drills into an existing 15mm pipe without cutting; no soldering required. For adding a washing machine connection to an existing supply.
• Embrass Peerless 15mm × ¾″ Angled Washing Machine Valve — £1.86
• Embrass Peerless 15mm × ¾″ Tee Washing Machine Tap — £3.20 — tee-pattern for adding a washing machine connection at an existing 15mm run

Flexible Tap Connectors with Isolating Valves

Pre-assembled flexible tap connectors with built-in isolating valve save time on kitchen and bathroom tap connections — one fitting provides both the flexible connection to the tap tail and the isolation point.

• Flexi Tap Connector c/w Isolating Valve 15mm × ½″ 300mm — £3.14
• Flexi Tap Connector c/w Isolating Valve 15mm × ¾″ 300mm — £3.94
• Flexi Tap Connector c/w Isolating Valve 22mm × ¾″ 300mm — £6.15

Boiler Filling Loop

• Embrass Peerless 15mm Filling Loop Straight — £9.68 — for re-pressurising sealed heating systems. Double check valve built in for Water Regulations compliance. Disconnect and store after use — the filling loop must not remain permanently connected.

The full Embrass Peerless valve range is stocked at APM's Acton trade counter — same-day collection available on all sizes.

APM Plumbing & Electrical | 24 Western Avenue, Acton, London W3 7TZ | 020 8702 8080 | apmi.uk