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Water Pressure
Background
Water companies are required to supply water for domestic purposes at a constant pressure that, under normal circumstances (but subject to a number of exceptions to allow for circumstances beyond their control), will “reach the top of the top-most storey of every building” within their area by gravity from a service reservoir or tank from which that supply is taken. This requirement does not apply to buildings that use pumped systems, such as blocks of flats.
What is defined as low pressure?
Since 1990 water companies have been reporting to Ofwat on the number of connected properties that receive pressure below the reference level when demand for water is not abnormal. This was known as the DG2 indicator. The reference level is defined as 10 metres head of pressure at a boundary stop tap with a flow of 9 litres per minute properties. This should be sufficient to fill a one-gallon container within 30 seconds. Over the past 20 years the number of properties at risk of low pressure has fallen significantly, largely as a result of mains renovation work, improved pressure management and some separation of shared supplies.