Low water pressure at home: common UK causes and what to check

"Low pressure" covers several different problems. Some you can check in ten minutes. Some belong to your water company. The first job is to work out which kind of system you have, because what is normal for one is a fault in another.

Pressure and flow

Pressure is how hard the water pushes. Flow is how much comes out in a given time. A tap can have decent pressure but poor flow because of a narrow or partly blocked pipe, and a shower can feel weak for either reason. Plumbers often measure both. You can get a rough idea of flow by timing how long a tap takes to fill a bucket of known size. Compare the result with the same test another day, or ask a plumber what to expect for your system.

Which system do you have?

Gravity-fed (low pressure) system. You will usually find a cold water cistern in the loft and a hot water cylinder in an airing cupboard. The hot taps, and often some cold taps upstairs, are fed by gravity from the loft. Pressure depends on the height between the cistern and the outlet, so an upstairs shower close to the loft can be weak. This is normal for the design.

Mains-pressure system. A combi boiler heats water directly from the mains, with no cylinder and usually no loft cistern. An unvented cylinder stores hot water at mains pressure, typically a sealed cylinder with safety valves and pipework, again usually with no loft cistern. In both cases the hot water pressure depends mostly on the incoming mains.

Mixed. Many homes have the kitchen cold tap on the mains and everything else gravity-fed. If the kitchen cold tap is strong and the bathroom taps are not, that points to a gravity system rather than a supply fault.

Common causes

A stopcock or isolating valve not fully open

After work in the house, the internal stopcock or a small isolating valve under a basin or on a pipe to a shower is sometimes left part-closed. Check that the stopcock is fully open (anticlockwise), then back it off a fraction so it does not stick. Isolating valves with a screwdriver slot are open when the slot lines up with the pipe. See finding your stopcock.

Limescale and debris

In hard water areas, scale builds up in shower heads, tap aerators and filters. If only one outlet is weak, unscrew and clean its head or aerator first. Combi boilers and some valves have inlet filters too, but anything inside the boiler casing is a job for a Gas Safe registered engineer.

Peak-time demand and shared supplies

Pressure can drop in the morning and early evening when everyone nearby is using water. Some older properties share a supply pipe with neighbours, so their use affects yours. If pressure is fine at night and poor at breakfast, that pattern is worth reporting to your water company.

A failing pump

If you already have a shower pump and the flow has dropped, the pump may be failing, airlocked, or its filters may be blocked. Check the maker's instructions. Electrical faults are for an electrician.

A problem on the water company's side

Burst mains, works in the street, or a fault in the company's network can all cut pressure. If the cold kitchen tap (on the mains) is suddenly weak and nothing has changed in the house, check your water company's website for incidents in your area, then contact them. They can also tell you what level of service they aim to provide. We have not quoted a statutory minimum pressure figure here because we could not confirm one from an official source.

A leak

An unexplained drop in pressure, along with a meter that keeps turning when everything is off, can mean a leak on the supply pipe. See finding a leak.

What will and will not help

• Gravity-fed shower that is weak: a shower pump can help, if it suits the system and the shower position. Read shower pump sizing first. A pump is not a fix for a mains-pressure system.
• Combi or unvented cylinder that is weak: a standard shower pump is the wrong product. Start with the incoming supply, the stopcock and the water company. Ask a plumber about the options. Do not try to boost the mains yourself; that can be a regulated arrangement.
• One outlet weak, everything else fine: clean the head or aerator, check the isolating valve, then look at that branch of pipework.

Is low water pressure my water company's fault?

Sometimes. If the incoming mains is weak at the kitchen cold tap with the stopcock fully open and no leak, contact your water company. If only the gravity-fed outlets are weak, it is more likely the design of the system.

Will a shower pump fix low pressure?

Only on a gravity-fed system with a cold cistern and a vented cylinder, and only with the right type of pump. It is not a universal fix.