Shower Power Booster

Easy | Efficient | Effective

Shower Power Booster

Easy | Efficient | Effective

Increase Pressure to or from a Combination Boiler - Shower Power Booster

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You may simply want to boost the flow and pressure of a shower or tap supplied with hot water from a combination boiler or protect the flow and pressure when someone opening a tap elsewhere in your home causes your shower to fluctuate. In more serious cases the combination boiler will shut down and run cold.

There are two reasons a Combi Boiler will shut down and they are:-

1.0 Insufficient hot water flow from the Combination boiler
2.0 Insufficient pressure before the Combination Boiler when water is demanded.

The Shower Power Booster will solve all of these problems and it is legal to fit one before or after a Combination Boiler.

It is perfectly safe to use our ShowerPowerBoosters boost water before and after a Combination Boiler and many hundreds of our customers have done so.

Will a ShowerPowerBooster  work for me

If the Combi Boiler drops out when you increase the flow of a tap or shower or open up a second tap there is a pressure problem, a double boost SP21S fitted before the combi boiler will support and boost a single tap or shower (or the whole house if only one tap or shower is used at any one time).

If the Combi Boiler does not drop out then the problem is after the boiler and a SP2B single boost or a SP21S double boost before or after the Combi Boiler can still solve your problem.

A Shower Power Booster will always work if its a pressure problem but it will not solve a capacity problem. The total output of a Combi Boiler depends on its KW rating:-

A 28 KW Combi Boiler can heat up to 13 litres of hot water a minute
A 36 KW Combi Boiler can heat up to 16 litres of hot water a minute
A 50 KW Combi Boiler KW can heat up to 25 litres of hot water a minute

If the capacity from your combi boiler is compromised because it has a problem in its heat exchanger or a blockage in the Combi Boiler itself, a showerpowerbooster cannot invent water that does not exist. Run multiple taps and showers and add up the total hot water flow in litres per minute hot water flow from each. Alternatively you can check the maximum output from the boiler by allowing the boiler to give an unrestricted flow from the boiler close to the boiler. If in doubt email our customer service team.


Fitting a single SP2B on the hot pipe to the shower only.

It will only boost the shower but it will also protect the hot pressure to the shower when someone opens a tap elsewhere in the house. ShowerPowerBoosters are the only pumps which can be fitted on hot side of a combi boiler. This is a great solution if you want to keep a shower going when the pressure fluctuates after the Combi Boiler. To find the pipe to fit the SP2B on simply run the shower only and find which pipe gets hot – thats the pipe to fit it on.

Click on the link below and go to Fig. 13 of the latest ShowerPowerBooster Information Manual:-

ShowerPowerBooster Information Manual

Fitting a SP21S before the combi boiler
This will boost all the hot in the house but if you use any other tap when the shower is running the tap will steal flow and pressure. Fit the pumps on the cold feed to the combi boiler.


You can protect and boost the pressure and flow to a shower after the Combi Boiler if you fit a ShowerPowerBooster on the hot and cold pipes which feed that shower (or tap). The Shower Power Booster is designed for high temperatures and pressures and is the only pump that is designed to boost on the hot side of a Combi Boiler.

When another tap is opened or a toilet flushed, a pair of ShowerPowerBoosters (one on the hot and one on the cold), can maintain a decent pressure and the shower or tap is not starved of water. Water would rather enter our pumps than leave via a tap so our pumps take priority over the tap and take the water they need and then boost the pressure in a priority greater than a tap.


To increase the pressure to a combination boiler you fit the ShowerPowerBooster on the cold pipe before a combination boiler. Our pumps can stop a combination boiler overheating or cutting out because of low pressure.

When boosting before a Combi Boiler please note that the maximum effective flow boost is up to 6 litres of water (which is the ideal output for a shower).

Combi Boilers have a pressure sensor which cuts out when the pressure is too low. They do this because if it were to heat just a small quantity of water it would ‘Kettle’ the water such that a small trickle of boiling water will be emitted. To avoid this a pressure sensor turns off the heating as soon as the pressure drops below the minimum pressure set by the manufacturer.

We recommend that if there is a problem with a combination boiler cutting out you fit two shower power booster pumps in series before the boiler (SP21S). For boosting taps and showers after a combination boiler a single pump will suffice.

Dependant upon the model of combi boiler the pressure switch will be set at between 1.0 bars and 1.5 bars (10 metres head to 15 metres head).

Unlike a traditional pump a ShowerPowerBooster can never hurt a Combination Boiler and a Combination Boiler can never hurt a ShowerPowerBooster.

You can boost showers or taps in your home up to the maximimum capacity of your combi boiler. 

To boost and protect a single shower the best solution is to boost the hot and the cold with the SP22S (gives you two automatic pumps). Each shower or tap you boost and protect needs an extra SP22S.

Combi Boiler Shower Booster

Buy a Combi Boiler Shower Booster

The WRight Choice micro booster cannot create hot water but it can take enough hot water to create the perfect shower. A good shower needs enough water to wash away the suds and enough pressure to give a nice forceful spray pattern. We aim to give 6 litres a minute and a minimum of 3 metres head to achieve this.


The maximum flow from a Combi Boiler is determined by its KW rating and in winter because water is colder so the output volume is less:
24KW Combi Boiler gives 11.5 Litres a minute (you can independently boost 2 Showers)
30KW Combi Boiler gives 14.5 Litres a minute (2.4 Showers)
42KW Combi Boiler gives 20 Litres a minute (3 Showers)

Combi Boiler – Hot Water Boost
The WRight Choice micro booster is the only pump on the market that can boost the pressure on the hot side of a combi boiler – you must not boost more than the maximum number of showers determined by your boiler.

The WRight Choice micro booster cannot create hot water but it can take enough hot water to create the prefect shower.

A good shower needs enough water to wash away the suds and enough pressure to give a nice forceful spray pattern. We aim to give 6 litres a minute and a minimum of 3 metres head to achieve this.

Combi Boiler – Inlet Pressure Boost

A WRight Choice micro booster on the cold inlet of a combi boiler will help protect your boiler even if your neighbours share a service to your house.


Combi Boilers are designed to switch off if the pressure falls so if you are in a house and someone turns on a tap you might just end up with your hot shower becoming a cold shower. To maximise the benefit of the pressure boost we normally recommend a double boost with the SP21S which will cost £155. If you bought just one pump (the SP2B at £125), you can buy an extra SP1U upgrade to double boost for £55.

The maximum flow from a Combi Boiler is determined by its KW rating and in winter because the water is colder the output is less.

For detailed advice specific to your home please contact our technical team on 01928 620 099 or email during office hours. Out of hours email