Water System - High - Pressure - Unvented

Water Systems - High Pressure - Unvented.

Houses built after 1985 in the UK may have a high pressure water system.

The mains water enters the property and flows through a stopcock. The stopcock
can be anywhere but is usually found under the kitchen sink.

Cold water at mains pressure (high pressure) runs to all of the cold taps,
showers, toilet cistern and other services. Water also runs through a pipe to a
hot water cylinder which is usually found in the airing cupboard.
The hot water cylinder stores water at mains pressure. This hot water
runs through pipes to all of the hot taps and showers. The hot water cylinder
is sealed and does not have a vent. The hot water cylinder is said to be unvented.

It is called a high pressure system because all of the pipes contain water at
a high mains pressure. The hot and cold water is at the same high pressure
and so the system is said to be balanced.
A balanced system is particularly suitable for showers.

The advantages of a high pressure system are
1. There is no tank of stored cold water in the loft.
This may give a better usage of the loft space (but see below).
2. The system is balanced which is suitable for showers.
3. The high pressure means that there is no need for a pump.

The disadvantage of a high pressure system is
that there is no tank of stored cold water in the loft.
If the mains water supply stops running due to maintenance
or a fault, then the property has no cold water.

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