Air Source Heat Pump Valves & Parts
An air source heat pump's outdoor unit and pipework are exposed to weather, frost and vibration in a way the rest of the system isn't, so the valves and parts protecting that external run matter as much as the heat pump itself. We stock anti-freeze valves, filters, balancing and bypass valves, hoses, isolators and control units that keep an installation running safely and efficiently, from brands including Inta, Caleffi, Fernox and Primary Pro. Many of these components are fitted as standard practice on a new installation, including an anti-freeze valve to protect against frost damage, a magnetic filter to catch debris, and a balancing valve to set the flow rate. Others, like installer packs and system fluid, cover maintenance and commissioning.
Whether you're a professional installer or a DIY enthusiast, at BES, you’ll find top-quality products designed to meet the demands of modern air source heat pumps. With free next-day delivery and competitive prices, we are a one-stop shop for heat pump installation and maintenance supplies.
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A Full Range Of Air Source Heat Pump Valves, Filters & Parts
The sections below group our range by function, covering the valves, filters and connecting parts most installations need, followed by the mounting and insulation accessories we stock separately in more depth elsewhere on the site.
Anti-Freeze Valves
An anti-freeze valve protects an ASHP's external pipework by discharging water when the temperature reaches a set point, before it can freeze and damage the system. Most models in our range open at 3°C and close again at 4°C. The Inta Zero Anti-freeze Valve - 1" BSP PM and the Caleffi iStop® Anti-freeze Valve - 1" BSP PM are the standard starting points, alongside two Caleffi variants worth knowing apart: the Caleffi iStop® High Temperature Anti-freeze Valve is rated for the higher primary-circuit temperatures used by some modern heat pumps, including R290 refrigerant models, while the Caleffi iStop® Plus Compact Anti-freeze Valve is a smaller-bodied version (H70 x W52mm) for tighter pipework spaces. For a lower-cost option, the unbranded Anti-freeze Valve - 1" BSP PM offers the same 3°C/4°C brass-bodied operation. All of these must be fitted vertically outdoors, with the outlet facing downwards, away from direct rain, snow or sunlight.
Full Bore & Filter Ball Valves
A full-bore ball valve provides unrestricted flow through the system when open, making it well suited to isolation points where pressure drop must be kept to a minimum. The Inta Full Bore Ext. Key Type Ball Valve - 1" BSP F Sw x 28mm Comp. is a straightforward isolation valve, while the Inta Full Bore Ball Valve with Filter Cartridge - 28mm Comp. and its 35mm equivalent combine isolation and filtration in a single fitting, useful where space doesn't allow for a separate in-line filter.
Flow Balancing & Fill/Flush Valves
Balancing valves regulate the flow rate of the heat transfer fluid through the system, which matters for a heat pump's efficiency in a way it doesn't for a standard boiler. The Inta INFSV2850 Heat Pump Flow Balancing Valve - 10 to 50 l/min sets the flow rate on its own, while the Inta INFBV28 Heat Pump Flow Balancing Valve with Fill & Flush - 4 to 40 l/min combines balancing with a fill and flush point in one valve. Where a dedicated fill and flush point is needed on its own, the Inta Fill and Flush Valve - 28mm allows the system to be filled, flushed and pressure-tested without disturbing other components.
Automatic Bypass Valves
An automatic bypass valve opens to maintain a minimum flow rate through the heat pump when other parts of the system restrict flow, protecting the unit from running dry or short-cycling. The Inta Automatic By-Pass Differential Valve - 28mm Angled suits a pipe run that changes direction at the valve, and the 28mm Straight pattern suits an in-line run, so the orientation can be matched to the pipework layout.
Heat Pump Filters & Air Separators
Magnetic filters protect a heat pump by trapping ferrous debris and sludge before they can reach and damage internal components, and air separators remove trapped air that would otherwise reduce flow and cause noise or corrosion. The range spans the intaKlean HP Heat Pump Magnetic Filter and the larger intaKlean HP XL, the CURA Heat Pump Magnetic Filter - 28mm, the Fernox Heat Pump Filter - 28mm, and the Sentinel Eliminator Vortex® 700 Heat Pump Magnetic Filter. For air removal, the Inta-vent Automatic Air Eliminator - 28mm is fitted at the system's highest point to vent trapped air automatically.
Heat Pump Hoses & Flexible Hoses
Pre-insulated heat pump hoses connect the outdoor unit to the system pipework while cutting down on heat loss at the connection point. The Intaflex Pre Ins. Heat Pump Hoses – 1" BSP F Swivel x 28mm Comp x 750mm Pair and the Caleffi Pre Insulated Heat Pump Hoses - 1.1/4" BSP F Sw x 35mm Comp x 500mm Pair, both available in swivel and elbow patterns across several lengths. Where pre-insulated hose isn't needed, the uninsulated Flexible Hose - 1" BSP F Swivel x 28mm x 1000mm, Pair, with stainless steel overbraid and plated end connections, is a lower-cost alternative.
Control Units
Rather than plumbing and wiring several separate valves and controls together on site, the Inta Hydra range packages them as one pre-built unit. The Inta Hydra Air Source Heat Pump Control Unit - Standard Assembly covers the base setup, and the version with 1 Actuated Valve adds motorised zone control for systems that need it.
Rotary Enclosed Isolators
A rotary enclosed isolator provides a local means of safely isolating the heat pump's electrical supply for maintenance or emergency shut-off. The Rotary Enclosed Isolator - 20 Amp and 32 Amp versions cover different circuit ratings - electrical installation and connection work should always be carried out by a qualified electrician.
Adaptors & Installer Packs
Where thread sizes need to be stepped up or down, the Inta Heat Pump Adaptor - 1.1/4" BSP PF x 1" BSP PM, Pair bridges the two most common heat pump connection sizes. For a complete starting point, the Inta Heat Pump Installer Pack - 28mm bundles two insulated heat pump ball valves, two Zero anti-freeze valves with insulation and guard protectors, two heat pump hoses, adaptors and a tube of Condensate Pro bond and seal sealant in one box, with a 35mm version also available. The Altecnic Heat Pump Pack takes a different combination, pairing two 1" BSP anti-freeze valves with an adjustable differential bypass valve (10 to 60 kPa) and a 28mm composite Dirtmagplus filter with strainer.
System Fluids & Maintenance
Where the system uses a glycol-based heat transfer fluid rather than plain water, the Fernox HP-EG Concentrated Heat Transfer Fluid - 20 Litres is diluted with mains water to the concentration needed for the required frost protection - for example, roughly 30% concentration protects to around -14°C, rising to around -33°C at 50% concentration, so check the product's full dilution table against your system's requirements before mixing. For sealing and upkeep, the Condensate Pro Bond & Seal Sealant - 290ml, Black creates a waterproof seal at insulation joints and wall penetrations, and the Condensate Pro Maintenance Coat - 250ml Tin is applied after fitting insulation or during an annual service to help protect it. A Condensate Collection Tray is also worth having on hand to catch condensate during commissioning or servicing work.
Protecting Heat Pumps From Freezing
Frost protection on an ASHP installation usually comes from more than one component working together: an anti-freeze valve to discharge water before it freezes, insulation on the exposed pipework and valves to reduce how quickly heat is lost in the first place, and, in some systems, a glycol-based heat transfer fluid instead of plain water for an extra margin of protection. None of these should be treated as a substitute for the others - check the heat pump manufacturer's own installation requirements for which combination applies to your system.
Wall Brackets & Drip Trays
Wall-mounted units are supported on brackets rated by weight, such as the Heat Pump Wall Bracket, 660mm 250kg with a matching drip tray underneath to catch condensation. See our full wall bracket range for every weight rating we carry.
Floor Mounting & Flexi Frames
Ground-level installs typically sit on a Flexi Frame Base or an AV Slab to reduce vibration and keep the unit level. Our full floor mounting selection has the complete size range.
Diamond Core Bits
Pipework routed through an external wall generally needs a core drilled first. Our installation accessories page lists the Diamond Core Bit - 91mm and 78mm sizes we stock.
Pipe & Valve Insulation
For the pipe run and valve insulation, joint covers, sealing rings, wall sleeves and backplate that finish off the job, our Primary Pro brand page walks through the full system in detail, including which Primary Pro insulation fits which specific anti-freeze or ball valve. A couple of items sit outside that range: the Primary Pro Elbow Insulation Joint Cover and Straight Insulation Joint Cover finish off insulated joints, and the Rubber Lined Clip - 68 to 74mm secures insulated pipe without crushing the covering.
Why Shop Air Source Heat Pump Parts At BES
With over 50 years supplying the heating trade and a broad stockholding across Inta, Caleffi, Fernox, Primary Pro and other established brands, we help installers source the specific valve, filter or fitting a job calls for rather than a generic substitute. Next working day delivery is available on qualifying orders, and our team can help track down a part if you're not sure which one you need.
For the wider selection of components used across an ASHP installation - buffer tanks, cylinders, pipe fittings and system fluids - browse our full Air Source Heating System Parts range, or head back to AC Installation Equipment for other supporting products such as condensate pumps, controls and ducting.
FAQs
What does an anti-freeze valve do on a heat pump?
It protects exposed external pipework from frost damage by automatically discharging water when the temperature drops to a set point, typically around 3°C, closing again once it rises slightly above that. It must be fitted vertically outdoors, with the outlet facing downwards.
What's the difference between the standard, High Temperature and Plus Compact Caleffi iStop valves?
The standard iStop suits typical installations. The High Temperature version is rated for the higher primary-circuit temperatures used by some modern heat pumps, including R290-refrigerant models. The Plus Compact version has a smaller body for tighter pipework spaces. All operate on the same 3°C/4°C discharge principle.
Do I need a magnetic filter on a heat pump system?
A magnetic filter isn't always mandatory, but it's widely fitted to protect the heat pump and other system components from debris and sludge. Some manufacturers require one to maintain their warranty. Check your heat pump's installation manual to confirm.
What's the difference between a balancing valve and a bypass valve?
A balancing valve sets and maintains a specific flow rate through the system, while an automatic bypass valve opens only when needed to maintain a minimum flow rate if other parts of the system restrict it. The two often work together rather than replace each other.
Can I use plain water instead of a glycol-based heat transfer fluid?
Many systems run on plain water with an inhibitor, but a glycol-based fluid such as Fernox HP-EG offers extra frost protection where the system is at greater risk of freezing, at a concentration matched to the protection needed - check your heat pump manufacturer's requirements before choosing between the two.
Do I need to insulate the pipework as well as fit an anti-freeze valve?
Yes - an anti-freeze valve and pipe insulation address different risks and work best together. Insulation reduces ongoing heat loss and slows how quickly exposed pipework cools, while the anti-freeze valve protects against the pipework actually freezing.
Can I install the electrical isolator myself?
No. Any electrical work on a heat pump's isolator or supply should be carried out by a qualified electrician in accordance with current wiring regulations.