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BES carry a wide range of correctly sized expansion vessels to meet your needs, including our new range of Robokit compact vessels for when space is tight. Both types are 8, 12, 18 litre capacity vessels with the standard range having 24, 35, 50, 80, and 105 litre capacity.

And if you are looking for safety relief valves, mounting brackets, filling loops or sealed system filling kits, we’ve got those too! Shop now for next-day delivery on central heating expansion vessels from top brands.

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An unbeatable range of expansion vessels

Expansion vessels, also known as expansion tanks, are found in most domestic pressurised heating systems – they are used to protect water heating systems from excessive pressure.

At BES, our expansion vessel range includes:

Expansion Vessels

Ranging from 0.16 litres to 105 litres, our top-quality expansion vessels are easy to install, with most having wall mounting options. Mini expansion vessel shock arrestors are also available in the selection.

Expansion Vessels Kits

Available in 8, 12, 18 and 24 litres, the expansion vessel and filling kits in this range include the expansion vessel, a wall mounting bracket, a 4-way manifold with washer, a safety relief valve, a pressure gauge and a filling loop with isolating valves. Robokit Compact Vessels and Filling Kits are also available in 8, 12 and 18 litre options.


Available in plastic, aluminium or acetal plastic, our range of tundishes come in various sizes, including 15x32mm, ½”x3/4”, ¾”, 15mmx22mm, 15mmx22mm compression and 22mmx1”. Combined tundish and non-return valves are also available.

Expansion Vessel Service Kits

The Pressure Vessel Service Kit we have available in this selection comes from Arctic Hayes, a top manufacturer of central heating parts.

Expansion Vessel Fixing Kits

Insta Safe-Group Vessel Fixing Kit and Insta Safe-Group Vessel Fixing Kit with NRV are among the most popular service kits available.

Expansion Vessel Adaptors

Our range of expansion vessel adaptors includes pressure vessel hand pump flexible adaptors and hand pump angled adaptors.

Byelaw Kits

The most popular kit in the collection is our Byekaw 30 Kit Complete, which contains a screened breather, a screened warning pipe unit, a dip tube bend, and a rubber grommet for vent/expansion pipes.

Filling Loops and Filling Kits

Our most popular filling kit for expansion vessels contains all the components required for a sealed system installation. Various straight and remote filling loops with valves or gauges are available in the range too.

Expansion Vessel Hand Pumps

Pressure vessel hand pumps from Hayes are available in our selection. The most popular hand pump is the heavy-duty pressure hand pump with a digital display, 0 to 8 bar gauge, suitable for Schrader valve connectors.

Cold Water Storage Tanks and Tank Lids

Rectangular cold water storage tanks in 18L and 114L options are available – made of plastic, out storage tanks are for feed and expansion and manufactured to BS 4213:2004 and WRAS approved.

Expansion Vessel Service Valves

Service valves for sealed heating system expansion vessels are available – the Expansion Vessel Service Valve ¾” BSP Union x BSP PM being the most popular among our customers.

Adjustable Hydrostats

Adjustable hydrostats, also known as water pressure switches, protect a sealed heating system’s components from operating when the pressure drops below a pre-set level  

Expansion Vessel Backplates

Water storage tank backplates are included in the range – with the most popular option being this tank backplate, which fits all cold water storage tanks.

Expansion Vessel Mounting Brackets

Mounting brackets for expansion vessels are available as separate parts. These can generally be used on expansion vessels of up to 25 litres – any vessel larger than that should be floor mounted.

Pressure Vessel Inflators

Our Cordless Expansion Pressure Vessel Inflator, the Vessel Jet 2, is the most popular hand-help cordless high-pressure air compressor we have in our selection.

The right central heating products for the job

At BES, we like to ensure our customers find every central heating fitting, part and accessory they may need. Our central heating fittings include valves, heating pumps, boiler equipment, heating controls, central heating filters and vents & more to suit a wide number of heating applications.

Expansion vessels delivered quickly

With over 15,000 products in stock and ready to ship for next working day delivery, you won’t have to wait around too long for your expansion vessel.

If you need help finding the right expansion vessel or any central heating product, contact our team, who will help you in no time.

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