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    Open vent boilers

    Summary: Open vent boiler guide, advantages of an open vent boiler and disadvantages of an open vent boiler.

    Open vent boilers

    This older type of boiler system has become quite dated and as a result people opt to adapt the open vent system into the similar, yet more effective sealed boiler system. The open vent boiler consists of a hot water storage cylinder, plus two water tanks located usually in the loft space. One of the tanks is fed water from the mains supply which in turn is sent to the hot water cylinder and is heated by the boiler. This heated water is sent from the cylinder to the taps in the house requiring hot water.

     Open vent Boilers - lets-do-diy.com


    • This system allows for a good flow of Domestic Hot Water (DHW) which is beneficial for larger homes in particular. Due to the fact that the water is stored and heated before it is needed, means that when it comes to being used, there is hot water in abundance. Other types of boiler such as the combination boiler have a reduced flow because the water is being heated as it is being used.
    • More than one hot tap or shower can operate at the same time without one or more running cold.


    • When the storage cylinder runs out, the user will have to wait for it to be resupplied and reheated. This takes some time.
    • Space is required for the hot water cylinder. This is normally located in an airing cupboard.
    • A lot of loft space is required for the two water tanks (feed and expansion tanks) that receive the supply from the mains water system. This is undesirable, particularly in smaller sized properties. The system of having tanks located in the loft can also cause problems if you wish to convert the loft into a living space. This is why many people convert the system into a more modern sealed boiler system which does not require tanks.

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