Guide to shower pumps

Installing a shower pump is the perfect way to boost the power of a shower that produces a disappointing flow of water. But deciding which shower pump is best for your needs can be hard. This shower pump buying guide will help.

It explains what a shower pump is, how it works and how to decide whether you need a shower pump. It also looks at the different types of shower pumps in detail and gives advice on installation and maintenance. Finally, it highlights some key things to consider before buying a shower pump and answers some frequently asked questions. 

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A shower pump is an electrical device used to increase the volume of water pumped through a property’s pipes to boost water pressure. It increases the pressure and flow rate of the water that comes through a shower head. A shower pump is used in homes with low water pressure.

There are a few factors to consider when determining whether a shower pump is needed:

• The water system:
  A shower pump can only be installed in properties with a gravity-fed (also called open vented) water system. This type of system is easily identified as it has a cold water storage tank (usually in the loft) and a hot water storage cylinder (usually in an airing cupboard).
  A shower pump must not be installed in a property with a combi boiler (no water storage) or an unvented water system (hot water storage only). This is because both systems use mains-fed water, and under British regulations, you cannot connect a shower pump to the mains water supply. These water systems generally have no issues with water pressure anyway, but if there is a problem, you can fit a booster pump (also called a whole house pump) which boosts the water pressure throughout the home.

• The type of shower installed:  
  Shower pumps can be used with manual and thermostatic mixer showers and electric showers. You won’t need one for a power shower as they have a built-in pump. And you may or may not need one for a digital or smart shower depending on whether the installed model includes a built-in pump.

• The water pressure:
  Although most gravity-fed water systems are low-pressure, the amount of pressure supplied can vary. And the amount of pressure needed can differ from one shower to another. For this reason, shower pumps are available to suit different water pressures and showers.

How to test water pressure

If you’re unsure whether the water pressure coming from an existing shower is low or high, there is a simple test you can do:

• Get a one-litre measuring jug and a stopwatch

• Place the jug under the shower head

• If it takes longer than six seconds to fill the jug, the water pressure is low, and a shower pump is needed.

• Turn the shower on and start the timer at the same time

• Time how long it takes to fill the jug to one litre

All shower pumps work on the same principle and have the same key parts. They consist of a box containing a motor and one or two internal impellers (another word for the pump) with water inlets (connected to the water supply) and outlets (connected to the shower). When the shower is switched on, water is fed into the inlet and through the impeller, which spins quickly and fires it out of the outlet hose. From there, it travels through the shower unit and then to the shower head.

For the water to go up against gravity, water pressure is needed. The amount of pressure gained (measured in bars) will depend on several factors, such as the distance the water needs to travel and the power of the pump and shower. Shower pump types can vary to serve different purposes and situations, which we cover in the next section.   

Due to the potential risks of mixing water and electricity, shower pumps must be fitted by a qualified plumber and electrician. The installation will take around an hour if the new pump is replacing an old one. It may take two to four hours if a new pump is installed, depending on the job's complexity and whether new pipework is needed. 

Where to install a shower pump: the best place is in the airing cupboard, at the base of the hot water cylinder. But if that’s not possible, it can be installed in the loft near the cold water tank.

Once the shower pump has been installed, it’s important to periodically carry out checks to ensure it’s working correctly and keep it well maintained. A broken shower pump isn’t just inconvenient; it can also lead to burst pipes and flooding causing severe damage to the home. And a clogged pump will reduce water flow and make more noise.

Shower pump checks and maintenance tips:

• Remove and clean the reservoir and filters with an anti-bacterial solution to remove limescale and sludge

• Descale the shower head

• Remove air locks (check the user manual to find out how to bleed a shower pump)

Note: Always ensure the electricity supply to the pump is switched off before carrying out cleaning and maintenance tasks.

The information above should help you decide whether you need a shower pump and which shower pump is best for the property. But there are a few more things to consider before making your final choice: 

1. Where do you want to fit the shower pump?
   The location of a shower pump, in relation to where the cold water storage tank and shower are, can significantly affect how well it boosts the water pressure and noise levels. For example, in a home with a loft, a positive head shower pump can be fitted in the airing cupboard next to the hot water storage cylinder or near the cold water storage tank. A negative head pump will be needed in a flat, where the pump will be on the same level as the water tank. If the pump is fitted in an airing cupboard, care must be taken to ensure it doesn’t get covered with towels or linen, as this will cause it to overheat and could cause serious damage. 

2. Which bar shower pump do I need?
   Water pressure is measured in bars, and every shower pump has a bar rating to indicate the pressure it can deliver. The higher the bar rating, the higher the pressure. The bar rating you need will depend on the size of the home, the size of the shower head and the hot water cylinder capacity. As a guide, install a 1.5-2.0 bar pump for a small flat or small shower head, a 2.0-3.0 bar pump for a two-bed house and large shower heads, a 3.0 bar pump for a three-bed home and a 3.6 bar pump for a house with four or more bedrooms with multiple showers. However, if the home has a small hot water cylinder, avoid installing a pump that’s 3.0 bar or above, as the hot water will run out very quickly.

3. What shower type do you have installed?
   If you’re fitting a shower pump to use with an existing shower, the type of shower installed will affect the type of shower pump you can have. If the shower is a manual or thermostatic mixer shower and you only want to boost the pressure of one water supply, fit a single impeller shower pump. But if you want to increase both the hot and cold water supply, install a twin impeller shower pump. An electric shower only uses a cold water supply, so you’ll need a single impeller pump. 

4. What pipe size do you have installed?
   The standard size for pipes in the UK is 22mm. However, some older homes may have 15mm pipes. Most shower pumps can only be fitted where there are 22mm pipes, but there are pumps available that cater to 15mm pipes. It’s essential that the right pump is installed, as 15mm pipes should never be connected to a pump designed for 22mm pipes.

5. What size shower pump do you need?
   Shower pump size comes down to the bar rating it can deliver rather than its physical size. And the size needed will be determined by the requirements of the home. For example, consider how much pressure is used to drive water to the taps and shower and how many water outlets are likely to be used simultaneously. If multiple showers and taps are used at one time in a large home with multiple occupants, the pressure requirements will be much higher than in a small house with two occupants.

6. What about the noise of the shower pump?
   Some shower pumps can be quite noisy, generating upwards of 70-80 decibels, this is because the vibrations produced by the shower pump’s mechanism and the way water is being moved at a high speed through the pump. However, shower pump products have improved over the years and there are now some shower pumps that make considerably less noise (from as little as 48 decibels) and are highlighted as having a ‘quiet operation’. There are also ways to reduce the noise by creating a stable shower pump platform, ensuring there are no loose floor boards beneath the pump, and using a pump mat and/or enclosure to absorb some of the noise.