A weak flow at the taps can have several causes, and a boiler is only one of them. Mains water pressure is a matter for the water company, up to a defined point on the supply, and it is worth knowing what that company must provide before paying for boiler or plumbing changes. This guide summarises the Consumer Council for Water (CCW) pages on low water pressure and on the Guaranteed Standards Scheme, and covers England and Wales. It is general information, not advice on a specific fault.

What the water company must provide

CCW says the Water Industry Act 1991 requires that a household receives water constantly and at a pressure that reaches the upper floor of the house. Ofwat, the regulator, has set that companies should maintain a minimum pressure in the communication pipe of seven metres static head, which is 0.7 bar. The communication pipe comes off the water main, belongs to the company and ends at the outside stop valve at the home.

CCW makes the limits clear. The company has no obligation to meet pressure requirements inside an external private supply pipe, whether shared or not, or inside the property. There is also no regulated upper limit, although CCW says internal plumbing should be able to withstand 10 bar to meet British standards. This distinction matters when a heating engineer or plumber says the problem is “the mains”: the company’s duty stops at the outside stop valve.

Signs and possible causes

CCW lists signs of low pressure: a shower that drops to a dribble when someone flushes a toilet or opens a tap, a bath that takes much longer than about five minutes to fill, and a toilet cistern that takes much longer than about 1 minute 40 seconds to refill. It lists possible causes including a burst on the main, repairs or maintenance in the area, high demand at particular times, cold weather, the company using another water source, a leak on the supply pipe, a shut valve, or a shared supply where others are using water at the same time. Several of these are inside the customer’s side of the outside stop valve, and others are the company’s responsibility.

How a boiler’s own flow rate and pressure affect a shower is covered separately in the guide to combi boiler flow rate and pressure.

What to record and report

CCW recommends recording the times of incidents of low or high pressure over a period, for example two weeks, and reporting them to the water company. It says the company can visit the property to test the pressure. A record with dates and times is also useful when a heating engineer needs to separate a boiler fault from a supply problem, for example before a boiler pressure problem is diagnosed.

Compensation under the Guaranteed Standards Scheme

The Guaranteed Standards Scheme (GSS) sets minimum standards required by Ofwat. If a company fails to meet a standard, CCW says it must make a fixed payment or credit the customer’s water services account. For low water pressure the company must ensure pressure of at least 7 metres head (0.7 bar) in the communication pipe, usually measured at the outside stop valve. If it fails to do this twice for more than one hour within a 28-day period, the entitlement is:

• England: £50, payable up to 5 times a year, and a customer who also experiences ongoing low pressure may be automatically entitled to £250 per year;
• Wales: £25, once per year.

CCW notes there are circumstances in which a GSS payment will not be made and points to Ofwat’s guidance for full information for both nations. It also says additional standards were introduced from 1 October 2025 as part of the GSS review, including for core priority services, customers in debt, meter readings, meter installation and water quality notices.

Other standards that can matter

Other GSS standards can arise around plumbing or heating work. For planned interruptions to supply the company must inform customers in writing at least 48 hours in advance in England (24 hours in Wales). The entitlement if it fails to do so is £50 in England and £20 in Wales, and payments for a late restoration of supply are £50 in England and £20 in Wales, with extra sums for longer interruptions. Appointments are also covered: the company must visit on the agreed day, within the morning or afternoon or a two-hour slot if requested, and give at least 24 hours’ notice of cancellation. The entitlement for failing to keep an appointment is £50 in England and £20 in Wales, except in circumstances such as severe weather.

FAQs

Does the water company have to fix low pressure inside my house?

No. CCW says the company has no obligation to meet pressure requirements inside the customer’s private supply pipe or inside the property.

How much is the low pressure payment?

In England £50, payable up to five times a year, with up to £250 a year for ongoing low pressure. In Wales £25 once per year. The standard is a failure to reach 7 metres head twice for more than one hour within 28 days.

Does this cover Scotland or Northern Ireland?

No. The CCW pages cover England and Wales.

The bottom line

In England and Wales the water company must keep pressure in its communication pipe at 7 metres static head (0.7 bar) or above, up to the outside stop valve, and pays a fixed sum under the Guaranteed Standards Scheme if it fails twice for more than an hour in 28 days. Pressure inside the customer’s own pipework and home is not the company’s responsibility. Recording the times of low pressure helps to separate a supply problem from a boiler or plumbing fault. This is general information, not personalised advice.

Sources

This guide draws on the following primary sources, current as of 25 September 2026:

• Consumer Council for Water, “Low water pressure”
• Consumer Council for Water, “What standards are guaranteed by water and sewerage companies?”

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Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.