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 Unvented Cylinders

What Is An Unvented Hot Water Cylinder ?


Unvented hot water cylinders provide stored hot water to properties in the same way that traditional open vented cylinders do. However, they differ in that they are fed directly by the incoming cold water mains supply. Therefore the hot water is stored under pressure.


As the cylinder is not fed by a tank (a sealed system), the water has to have provision for it to expand when it is heated. This is provided by fitting an expansion vessel to the supply pipe work to the cylinder (along with other safety devices), or in some cylinders this expansion is taken up by internal expansion air. The cylinder then provides stored hot water at mains pressure and flow rates. The pressure & rate of which is determined by the incoming cold water main.


Positives Of Unvented Cylinders


1. Stored hot water at mains pressure & flow. 2. There is no need for cold water storage tanks within loft spaces. 3. There is no need for booster pumps to improve flow rates, removing the noise, maintenance, cost, and inefficiency of booster pumps. 4. Multiple hot water outlets (taps) can be used simultaneously.


Negatives Of Unvented Cylinders


1. Performance is determined by the incoming cold water main, therefore a 22mm incoming cold water main is usually required for optimum performance. 2. An expansion vessel, and safety pressure reducing/relief valves have to be fitted to ensure the cylinder operates safely. 3. The cylinder has to be fitted in an area where the safety pressure relief pipe work can be run to ground level externally.




Vaillant Unistore Unvented Cylinders -


- 2 Year Manufacturer Guarantee.


- 25 Year Manufacturer Guarantee on outer shell.





We recommend, supply, & fit the Vaillant Unistore Unvented cylinder range.


Available in a range of six high grade duplex stainless steel cylinders from 120 to 310 litres, to suit all domestic property requirements.