Water pressure

What is water pressure?
Pressure is the force that pushes water through pipes. Water pressure determines the flow of water from the tap. If pressure is not sufficient then the flow can reduce to a trickle and it will take a long time to fill a kettle or a cistern.

What causes low water pressure?
For some customers, the problem is caused by sharing a supply pipe from the water main. This can be a problem if the pipe is too small; in poor condition; or if customers sharing a supply frequently use water at the same time. Householders are responsible for the supply pipe from their property to the external stop tap (X on the diagram below).

The diagram shows householders’ responsibilities:

Houses B and C have a shared supply pipe
Houses B and C have a shared supply pipe and have joint responsibility for maintenance of any part of the pipe that is shared.

Houses D, E and F are terraced houses with a shared supply pipe. They share responsibility for maintenance of the pipe.

In some cases pressure problems are caused by the customer’s own pipework. For example a damaged or leaking pipe or a partially closed internal stop tap. In other cases, customers’ pipes are old and have become corroded, restricting the water flow. In these cases the water company is not responsible for solving the problem.

Other causes of low pressure can be the responsibility of water companies, such as:
Short-term reductions in pressure caused by routine maintenance and improvements of water mains.
In-adequate pumping facilities
The water main too small; or
reduced pressure from the water main caused by leakage, equipment failures or
blockage of the service pipes.
Pressure can also be affected by the height of a customer’s property, i.e. properties at the top of a hill may receive lower pressure than properties which are at the bottom of the hill.

Pressure varies during the day depending on the demand for water placed on the supply system. When demand is high (for example in the morning and early evenings), pressure can be lower than during the rest of the day. There can also be problems during dry spells when people are using sprinklers and hosepipes to water their gardens.

What standard are the companies legally obliged to meet?
Companies are required to supply water constantly and at a pressure which will reach the upper floors of houses. This does not apply to buildings that use pumped systems, such as blocks of flats.

Who monitors performance on water pressure?
The water companies collect information on water pressure to identify pressure and supply problems and the need for leakage control.

We require companies to report annually on their performance. This is measured against a standard set by us. The standard is called a level of service indicator (known as DG2). This measures the number of properties at risk of experiencing water pressure below the standard.

The DG2 measure is ten metres head of pressure, at the external stop tap, at a flow of nine litres per minute. This should be sufficient to fill a one-gallon (4.5 litre) container in 30 seconds. This level of pressure does not override the duty to supply water constantly at a pressure to reach the upper floors of properties.

How many properties suffer from low pressure?
Company data supplied to Ofwat in 2003 shows that under 15,000 properties suffer from pressure below the reference level.

Since privatisation companies have made significant reductions to the number of properties suffering from low pressure. In 1990-91 around 380,000 properties suffered from low pressure.

What action can companies take to improve pressure?
Renovate the water main by scraping away any corrosion and putting in a new lining.
Replacing the main with a larger one.
Installing pumps to boost the pressure.

What should you do if your water supply has poor pressure or an inadequate flow.?
The first step is to check that there is not a problem with your plumbing, such as a partially closed internal stop tap (if fitted) or a water leak. If the problem cannot be resolved you should contact your water company who can take pressure and flow measurements and determine whether the problem lies with them or your pipes or the water companies’ pipes

Can I claim compensation for low pressure?
You are entitled to a payment if the company fails to maintain water pressure. Customers affected by low pressure on two occasions, each lasting an hour or more in a period of 28 consecutive days, are eligible for a sum of £25. The company must either pay you or credit your account.
Claims for compensation must be made to the company, in writing, within three months of the last of the two occasions of low pressure.

What else can affect your water pressure?
Some modern heating appliances and showers will not work below certain pressure levels. It is important that customers seek advice from the water company before this type of equipment is installed to check whether the pressure in their area is sufficient for these systems to operate efficiently.

For further information
e-mail: enquiries@ofwat.gsi.gov.uk