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Expansion Vessels

Expansion Vessels

Whisper Pumps stock a comprehensive range of Expansion vessels from the globally leading thermo-hydraulic manufacturer Zilmet.

Expansion vessels or pressure vessels are used in pump systems to store water under pressure and are used in conjunction with a pressure switch.

Inside the tank is a rubber membrane: on one side of the membrane is air and on the other side is water. When the pressure switch starts the pump, water is forced into the pressure vessel which causes the membrane to expand, compressing the air on the other side of the membrane. When the set pressure is reached, the pressure switch stops the pump and the non return valve closes, holding the pressure in the system. When water is drawn from the system, the air pressure forces water out until the pressure falls to the lower set level of the pressure switch at which point the pump re-starts and the cycle is repeated.

In heating systems, expansion vessels are used to absorb the thermal expansion and contraction of the fluid in the system.
Please call us on 01777 871100 or contact us through our online form for help in selecting the right  expansion vessel for your application.


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Zilmet Ultra Pro Pressure Vessels
Zilmet Ultra Pro pressure vessels with replaceable butyl membrane are expansion vessels ..
Zilmet Cal-Pro Central Heating Expansion Vessels
Zilmet CAL-PRO - are membrane expansion tanks for closed circuit central heating systems. C..
Zilmet Central Heating Boiler Expansion Vessels
Zimet OEM-PRO replacement  expansion vessels for central heating boilers. The wide ran..
Zilmet Hydro Pro Expansion Vessel
Zilmet Hydro Pro expansion vessels or pressure vessels, with fixed butyl diaphragm and r..
Zilmet INOX Pro Expansion Vessels
Zilmet Inox-Pro stainless steel expansion vessels for aggressive water conditions. ..
Zilmet Intafil
Zilmet's Intafil sealed heating system filling kit including a filling loop, double check valve an..
Replacement Ultra Pro Membranes
Replacement membrane for Zilmet Ultra Pro expansion vessels, in butyl rubber for drinking wat..
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Newark, Nottinghamshire, NG22 9ZD