Mains booster pumps for low water pressure

When every tap in the house is weak, including the kitchen cold tap on the mains, people start looking at booster pumps. A whole-house mains booster is a pump, often with a storage tank or a pressure vessel, that raises the pressure and flow of the cold supply to the whole property. It is a bigger, more regulated job than most people expect. It is also not the first thing to try.

A booster is not a shower pump

A shower pump is made for a gravity system. It takes water from a loft cistern and a vented hot cylinder and pushes it to one shower or one bathroom. Shower pump sizing and shower pumps compared cover those. A standard shower pump is the wrong product for a combi boiler or an unvented cylinder.

A mains booster works on the cold supply coming into the house. It is aimed at homes where the incoming mains itself is the problem. Boosting the mains feeds everything after it: taps, toilets, a combi boiler or an unvented cylinder, and appliances. That is why it is a different product, sized and installed differently, and why the water company has an interest in it.

Before you look at a booster

Low pressure has many causes that a pump will not fix and may hide. Work through these first, using low water pressure:

• The stopcock. A stopcock that is only partly open, or an outside stop valve that has been half-closed, can throttle the whole house. See stopcocks and water meters.
• A leak. A leak on the supply pipe can steal flow and pressure. A pump would just push more water out of it.
• A pressure reducing valve. If one is fitted, it may be set low or partly blocked. See pressure reducing valves.
• Old or narrow pipework. A long run of small or furred-up pipe can limit flow even when the mains is good. Replacing it can be a better fix.
• The water company. If pressure has dropped suddenly, check for problems in your area and contact the company. It can tell you what level of service it aims to provide.

A pressure and flow reading helps you and a plumber see whether the incoming supply is genuinely poor. Water pressure testing explains how to take one and what it can and cannot tell you. Flow, how much water arrives, matters as much as pressure. A booster cannot create flow that the mains does not deliver.

Tank-fed and direct boosting

There are two broad ways to boost a supply.

Tank-fed (break tank) systems. Mains water fills a storage tank through a float valve, and the pump draws from the tank, not from the mains. The tank breaks the connection between the pump and the public supply, so the pump cannot pull water away from neighbours or push water back. It also gives a reserve to draw on at busy times. These systems need space for the tank, often in a garage, utility room or loft, and the tank must be covered and suitable for drinking water.

Direct boosting. The pump is connected to the incoming supply pipe and draws straight from it. This takes less space, but drawing directly from the mains can reduce pressure for others nearby, and the water company may restrict it or set conditions. Some systems sense the incoming pressure and only boost when it falls.

Which is suitable depends on the supply, the house and the water company's view. A plumber familiar with boosting, ideally one in an approved contractor scheme, should design it.

Notification and the rules

Regulation 5 of the Water Supply (Water Fittings) Regulations 1999, as made, lists "a pump or booster drawing more than 12 litres per minute, connected directly or indirectly to a supply pipe" among the installations for which the installer must give notice to the water undertaker and not begin work without its consent. That is the text as originally made; check the current version and ask your water company before buying anything. Scotland and Northern Ireland have their own water fittings rules. Backflow protection is also part of the design, covered in check valves and backflow.

Noise, space and power

Boosters run whenever water is used, sometimes for a moment when a toilet refills at night. Ask where it will go, how it is mounted and what noise the maker states. A pump in a cupboard next to a bedroom can be a nuisance. Tank systems need space and access for cleaning the tank.

A booster needs an electrical supply. Connecting it is for a qualified electrician. In England, Approved Document P explains when electrical work must be notified. We do not give wiring instructions.

If the house has a combi boiler or an unvented cylinder, raising the incoming pressure affects them too. Their makers set limits for incoming pressure. Anything on a gas boiler is for a Gas Safe registered engineer, and an unvented cylinder needs a competent installer; see when to call a Gas Safe engineer.

Is a mains booster the same as a shower pump?

No. A shower pump boosts water from a loft cistern to a shower on a gravity system. A mains booster raises the pressure of the incoming cold supply for the whole house, and has to meet the water company's requirements.

Do I have to tell the water company before fitting a booster?

Regulation 5 of the 1999 Regulations, as made, lists a pump or booster drawing more than 12 litres per minute from a supply pipe among the installations that need notice and consent. Check the current rules with your water company before work starts.

Will a booster pump fix low pressure from a leak?

No. A pump will push more water out of a leak and can hide the real problem. Find and fix leaks, check the stopcock is fully open, and talk to the water company first.