Stopcocks for UK Plumbers — 15mm, 22mm and 28mm Brass, MDPE and Stopcock Keys

The stopcock is one of the most important components in any water supply system. As the primary means of isolating the mains cold water supply to a property, a reliable stopcock is the first thing a plumber reaches for when a pipe bursts, a fitting fails, or a new appliance needs commissioning. APM Electricals stocks a comprehensive range of Embrass Peerless stopcocks in 15mm, 22mm and 28mm — including traditional brass capillary and compression types, MDPE service pipe variants, and the stopcock keys needed to operate buried boundary stopcocks — covering everything a trade plumber needs for both copper and blue MDPE supply pipe installations.

What is a Stopcock?

A stopcock is a straight-pattern valve with a rising spindle and tapered plug mechanism that controls the flow of mains cold water through a pipe. Unlike a gate valve — which is suited to gravity-fed low-pressure systems — stopcocks are specifically designed for use on mains pressure pipework and must comply with BS EN 1213 for water supply applications. They are approved to WRAS standards for use with potable (drinking) water and are the recognised fitting type for main supply isolation throughout UK domestic and commercial plumbing.

Stopcocks are fitted at the mains inlet (typically where the supply pipe enters the property), under kitchen sinks, before water meters, and at service entry points. They may also be installed on individual branch supplies to allow zone isolation without shutting off the entire property. Every property should have at least one accessible internal stopcock, and identifying its location is one of the first things a trade plumber should establish when attending a callout.

Brass Stopcocks — 15mm, 22mm and 28mm C×C

The most common stopcock for UK residential plumbing is the 15mm brass stopcock with capillary (C×C — copper-to-copper) ends. These are soldered into copper pipework using standard end-feed technique and offer a permanent, corrosion-resistant joint suitable for mains pressure cold water supply.

The Embrass Peerless Trade Stopcock C×C Brass 15mm is the van-stock workhorse for any domestic plumbing installation or replacement. At £4.42, it meets BS EN 1213, is WRAS approved and incorporates a renewable headwork with a jumper valve for easy maintenance. The lead-free brass body conforms to current drinking water regulations and is compatible with Type B copper tube to BS EN 1057. Its compact design allows installation in tight spaces under sinks or in floor cupboards.

For larger branch and distribution applications, the 22mm version at £7.26 handles higher flow rates on main branch runs — typically used where 22mm pipework distributes water across multiple floors or to multiple appliances from a single supply. The 28mm brass stopcock at £13.15 is specified for high-volume commercial or multi-unit residential installations where flow capacity must be maximised.

Embrass Peerless also supply a double-ended compression version for plumbers who prefer a compression connection or where soldering is not practical (e.g. in areas where a naked flame cannot be used). These share the same BS EN 1213 approval and WRAS certification as the capillary range.

MDPE Stopcocks — Blue Service Pipe Connections

Where the external supply is run in blue MDPE (Medium Density Polyethylene) pipe — the standard for underground water service pipes in the UK — a dedicated MDPE stopcock is required. These valves incorporate a compression fitting on one or both ends sized to grip the outside diameter of MDPE pipe, which runs from 20mm to 32mm OD depending on the service size.

Embrass Peerless manufacture a full range of MDPE stopcocks to suit the most common transition points between MDPE service pipe and internal copper or MDPE distribution:

• 15mm × 20mm MDPE Stopcock — £7.10 — internal 15mm copper to 20mm MDPE service pipe. The most common transition at the meter or boundary stop.
• 15mm × 25mm MDPE Stopcock — £6.34 — internal 15mm copper to 25mm MDPE. Standard for typical residential supply connections.
• 22mm × 25mm MDPE Stopcock — £10.82 — for 22mm internal distribution connecting to 25mm MDPE service.
• 25mm × 25mm MDPE Stopcock — £16.33 — full 25mm MDPE to 25mm MDPE for all-plastic installations.

MDPE stopcocks require a separate internal support sleeve (grab ring insert) to be fitted inside the MDPE pipe end before tightening the compression nut. This prevents the softer plastic from deforming under the grip of the compression olive. Always use the correct insert for the pipe OD — inserts are not universal across different pipe diameters.

MDPE stopcocks are approved for below-ground installation in communication pipes and are manufactured in lead-free brass to comply with The Water Supply (Water Fittings) Regulations 1999.

Drain-Off Adaptors

For installations requiring a drain point at the low level, the Stopcock Drain-Off Adaptor at £3.03 converts a standard stopcock into a combined isolation and drain-down point. This is useful in properties where the mains supply enters at a low level and a drain-off point is needed for winterising or pipe replacement without disturbing the main stopcock body.

Stopcock Keys — Operating Boundary Stopcocks

The boundary stopcock (also called the external stopcock or curb stop) is buried in the public footpath or road verge and controls the supply to an individual property from the water main. It can only be operated with a purpose-made stopcock key — a long rod with a fitting that engages the square or crutch spindle of the buried valve.

Having the right key is essential for emergency isolation, particularly when the internal stopcock is inaccessible, damaged or frozen. APM stocks three key types:

• 35" Multi-Purpose Stopcock Key — £16.99 — suits most standard square-head boundary stopcocks to a depth of approximately 900mm. The multi-head design engages both square and crutch patterns.
• 43" Multi Stopcock Key — £19.99 — for deeper boundary boxes where the spindle sits below standard 35" reach. Recommended for any plumber attending emergency callouts across a mixed property stock.
• 42" × ½" Square Pattern Stopcock Key — £18.23 — dedicated square-head pattern for older square-spindle stopcocks commonly found in pre-1970s properties.
• 43" Crutch Pattern Stopcock Key — £18.99 — for crutch-head (T-bar) spindle configurations found on some water utility infrastructure.

A 35" multi-key covers the vast majority of residential callouts. The 43" version is a sensible addition for any trade plumber dealing with older housing stock or properties with deep service boxes.

Regulatory Requirements

Under The Water Supply (Water Fittings) Regulations 1999, all fittings used on the mains supply must be WRAS approved (or equivalent) and appropriate for the working pressure of the supply — typically up to 12 bar in UK domestic systems. Stopcocks used on potable supply must meet BS EN 1213 and must not be manufactured with materials that could contaminate drinking water. Embrass Peerless stopcocks are fully compliant and WRAS listed.

Water Regulations also require that every property has an accessible isolating valve on the mains inlet, and that any replacement stopcock is installed in a accessible position with a minimum 0.5m clear space for operation. Where the original stopcock location is inaccessible, the fitting of an additional secondary stopcock in an accessible location is recommended.

Choosing the Right Stopcock

Stock the Full Stopcock Range

APM Electricals holds 18 stopcock SKUs in active stock — covering every size and connection type from the standard 15mm brass CxC through MDPE service connections to operating keys. For trade plumbers, maintaining a pair of 15mm brass stopcocks on the van avoids the delay of a dedicated supply run when an emergency call-out turns into a planned replacement. Adding a 35" stopcock key ensures that if the internal stop is jammed or inaccessible, the boundary can be shut without waiting for a water authority crew.

Orders placed before 3pm on weekdays are dispatched same-day on a next-day tracked service. Trade account enquiries welcome — contact the APM team for volume pricing on stopcocks and service pipe fittings.

APM Electricals — 24 Western Avenue, Acton, London W3 7TZ | 020 8702 8080

Embrass Peerless Trade Stopcock C×C Brass 15mm

The standard domestic mains isolation stopcock. BS EN 1213, WRAS approved, lead-free brass body, renewable headwork. Van-stock essential for every plumber. 15mm capillary ends.

£4.42 inc VAT

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Embrass Peerless Stopcock Brass 22mm C×C

22mm capillary stopcock for branch and distribution mains. Full-bore brass body to BS EN 1213, WRAS listed, suitable for mains pressure cold water. Higher flow capacity for multi-appliance feeds.

£7.26 inc VAT

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Embrass Peerless Stopcock MDPE Brass 15mm × 25mm

Transitions from 15mm internal copper pipework to 25mm external blue MDPE service pipe. Compression ends, WRAS approved, lead-free brass, suitable for below-ground installation. Standard for residential service connections.

£6.34 inc VAT

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43" Multi Stopcock Key

Operates square and crutch-head boundary stopcocks to a depth of 43 inches. Essential for emergency isolation of deep external stopcocks. Multi-head design suits the majority of UK water authority configurations.

£19.99 inc VAT

View stopcock keys at APM Electricals