Ball Valves: Full-Bore, Standard Port, and Lever vs Keylock — A UK Trade Guide

Ball Valves: Full-Bore, Standard Port, and Lever vs Keylock — A UK Trade Guide

Ball valves are the standard isolation device in modern UK plumbing and heating systems. They replaced gate valves as the preferred choice because they are quarter-turn (fast to operate), reliable when left unused for years, and available in full-bore configurations that cause minimal flow restriction. This guide covers the types, sizes, and correct applications for ball valves in domestic and commercial settings.

How a Ball Valve Works

A ball valve contains a drilled sphere (the ball) rotated by an external handle. When the hole through the ball aligns with the pipe, flow is unrestricted — fully open. Rotating the handle 90° turns the hole perpendicular to the pipe, blocking flow completely. This simple mechanism makes ball valves fast to operate and gives a clear visual indication of position: handle in line with the pipe = open; handle across the pipe = closed.

Unlike gate valves, ball valves do not suffer from galling or seized stems when left in position for extended periods — a significant advantage in heating systems where isolation valves may not be operated for years. When a gate valve seizes, it often fails to close fully; a ball valve that has not been operated in years typically still closes reliably on first use.

Full-Bore vs Standard Port (Reduced Bore)

This is the most important specification difference to understand:

• Full-bore ball valve: The hole through the ball is the same diameter as the pipe bore. A full-bore 22mm ball valve allows the same flow as 22mm pipe. There is negligible pressure drop across the valve when open. Use these on central heating primary circuits, boiler connections, and any application where pressure drop matters — particularly where the valve feeds a pump or the system is margined on pressure.
• Standard port (reduced bore) ball valve: The hole through the ball is smaller than the pipe bore — typically one pipe size smaller. A 22mm reduced-bore valve may have a 15mm bore internally. This creates a pressure drop when open, effectively behaving as a restriction in the pipe. Standard port valves are cheaper and acceptable for low-flow isolation applications (cold supply to a toilet cistern, supply to a garden tap) where flow rate is not critical. Do not use reduced bore on central heating primaries or boiler connections.

Always specify full-bore for central heating systems. The additional cost over reduced bore is minimal, and a reduced-bore valve on a heating circuit can cause pump cavitation, circulation problems, and noise.

Lever Ball Valves

The standard ball valve for UK plumbing and heating — a brass body with a lever handle that indicates position clearly. Available in compression, BSP (threaded), and push-fit connection types. The lever handle can be removed or a handle lock fitted to prevent accidental operation — useful in commercial or semi-public settings.

Standard lever ball valves are available in sizes from 3/8" BSP (10mm compression) up to 2" BSP (54mm compression) and beyond for commercial applications. For domestic heating and plumbing the common sizes are:

• 15mm (1/2" BSP): Cold water supplies to taps, toilets, washing machines; heating connections to radiators and UFH manifolds; outside tap isolation.
• 22mm (3/4" BSP): Central heating flow and return primaries; mains cold water main isolation inside the property; boiler primary connections on small systems.
• 28mm (1" BSP): Larger heating systems, commercial boiler connections, high-flow domestic systems.
• 35mm and 42mm: Commercial and light industrial; main isolation on larger buildings.

Keylock (Lockable) Ball Valves

A keylock ball valve replaces the lever handle with a slotted plug that requires a specific key (usually a flat-blade key or a dedicated T-key) to operate. The valve cannot be opened or closed without the key. Applications:

• Main cold water supply stop valves — prevents tampering or accidental shutdown in commercial premises
• Roof tanks, boiler house feeds, and any plant room valve that should only be operated by authorised personnel
• Outside taps and communal areas in HMOs and flats

Keylock ball valves look identical to a standard ball valve body — the only difference is the operating mechanism. Buy keys in spare sets and store one with the system documentation.

Mini Ball Valves (Service Valves / Isolation Valves)

Mini ball valves — also called service valves or isolation valves — are compact quarter-turn valves used for isolating individual appliances and fittings. The handle is a small flat-blade slot operated by a screwdriver rather than a lever. Common configurations:

• Straight service valve: In-line isolation, 15mm compression both ends. Used under sinks and wash basins to isolate taps, or on tails of ball valves feeding cisterns.
• Angled service valve: 90 degree turn, 15mm compression x 1/2" BSP male. Used where the pipe comes up through the floor or out of a wall and connects to a flexible tap connector — the most common fitting under sinks and basins.
• Radiator service valve: Isolates individual radiators without draining the system. Required by good practice on every radiator for future maintenance.

Service valves must always be installed with the slot position clearly visible — slot in line with pipe = open, slot across pipe = closed. Do not bury service valves behind panels or in inaccessible positions without providing an access hatch.

Drain-Off Valves (Drain Cocks)

A drain-off valve (drain cock, BS 2879) is fitted at the lowest point of a heating system to allow draining for maintenance. Standard fitting is 1/2" BSP male with a hose union outlet. Quarter-turn ball type drain valves are now preferred over the older screw-down type as they drain faster and reseal more reliably.

Connection Types: Compression, BSP, Push-Fit

• Compression ends: Standard for copper pipe. Reliable, demountable, no solder required.
• BSP threaded: For boiler flow/return ports (typically 3/4" or 1" BSP), manifold connections. Use PTFE tape or WRAS-approved jointing compound on all threads.
• Push-fit ends: JG Speedfit, Hep2O compatible. For central heating (up to 95 degrees C) use brass push-fit ball valves — check temperature ratings on plastic push-fit variants.

Gas Isolation Valves

Ball valves for gas isolation are a distinct product category and must be specifically approved for gas service. A standard plumbing ball valve must never be used on a gas line. Gas ball valves carry CE marking and conform to EN 331. Installation of gas isolation valves must be carried out by a Gas Safe registered engineer.

Specification Checklist for Heating Systems

• Full-bore on all heating primaries and boiler connections
• Working pressure: domestic heating typically 1.0–2.5 bar; standard PN10 rated brass ball valves are adequate
• Working temperature: all brass compression ball valves are suitable to 100°C+; verify plastic push-fit variants
• Drain-off valve at lowest system point, accessible with hose union connection

Ball Valves at APM Plumbing & Electrical

APM stocks a full range of ball valves for plumbing and heating applications — full-bore lever ball valves in 15mm, 22mm, and 28mm compression; BSP-threaded isolation ball valves; keylock security valves; mini service valves (straight and angled); radiator isolation valves; and drain cocks. All ball valves are brass-bodied and rated for domestic heating and plumbing temperatures and pressures.

Browse our ball valves and isolation valves or contact the Acton trade counter for project quantities. Trade orders placed before 2pm ship same day across London and the South East.

Products Available from APM Plumbing & Electrical

Key ball valves and lever valves available for trade collection or delivery:

Get It from APM Electricals

APM Electricals, 24 Western Avenue, Acton, London W3 7TZ. Call 020 8702 8080 or visit www.apmi.uk for same-day trade counter collection and next-day delivery across London and the UK.