In an unvented central heating system, water is stored at mains pressure in unvented hot water cylinders before it is distributed around the home. This pressure is maintained due to the system being unvented – so no pressure can escape.
Vaillant’s hot water cylinders work by cold water being fed through a pressurised tank, inside which it is heated. This hot water is then forced into the hot water cylinder at mains pressure by the incoming cold water – from here it is then supplied directly to any outlet that requires it.
The storage of this hot water at mains pressure has many advantages in a domestic property:
It is important that the correct size of hot water cylinders are installed in domestic properties so that they best meet the requirements of the occupants. The average person uses between 35 and 45 litres of water per day, so based on this a 200 litre tank should be adequate supply for a four person family each day.
This does not take into account other factors though, such as some family members taking longer in the bathroom than others, some family members that may prefer to take a bath every day rather than a shower and the installation of a dishwasher or power shower. The simple act of taking a bath rather than a shower could double your daily ‘average’ usage.
It is therefore important that when looking at hot water cylinders you carefully consider the size. It may be beneficial to install a cylinder that may seem too large for your property rather than installing one that is too small and then having to replace it.