How To Increase Water Pressure In Shower With A Combi Boiler

Low water pressure is a problem in many homes that have combi boilers and homeowners frequently seek methods to increase water pressure, particularly for the shower.  If you have a combi boiler, your options for increasing shower pressure are limited, below is an explanation of combi boilers and the various options for increasing the pressure of your shower.

How To Increase Water Pressure In Shower With A Combi Boiler

Because combi boilers work under pressure and are supplied water directly from the mains, water pressure has a big affect on them.  Some ways to increase water pressure include installing a booster pump, clearing blockages, checking the mains water valve, and checking for leaks around the house.

image of a shower with low water pressure
low water pressure with a combi boiler affecting the shower

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What is low water pressure?

According to Ofwat, the UK’s water sector regulator, low water pressure ‘can be caused by sharing a supply pipe from the water main. This can be a problem if the pipe is too small; in poor condition; or if customers sharing a supply frequently use water at the same time.’

Water pressure is measured in bars, and one bar is the amount of force required to force water up 10 meters high.  If water pressure drops below a minimum level, say 1 bar, the water flow rate may be reduced or the boiler will not start so only cold water comes out from the hot tap.

The pressure of water is measured in bars. One bar is the amount of force required to shoot water 10 metres into the air. The minimum pressure a property should have is one bar.  Three to four bars in your plumbing is considered good.

image of a water pressure guage
water pressure gauge

Combi boilers: Problems with low water pressure

The flow of water from your tap depends on the force of water that is pushing through pipes leading to your home.  Low pressure results in taking longer to fill things with water such as kettles and baths. 

Combi boilers and some showers will not work properly if water pressure is low.

If your water pressure becomes too low, you’ll have a barely-there shower and possibly a lack of hot water throughout the house.

Too high, and the pressure from your outlets will be irregular, potentially resulting in leaks and banging in your pipes.

If you’ve got a combi-boiler, it can be a little more challenging to increase the water pressure in your shower.

This is because a lot of methods used with a non-combi boiler (such as installing pumps and boosters) cannot be used with a combi-boiler.

Combi-boilers perform best with flow rates of 12 to 15 litres per minute. Low water pressure can cause low water flow rates so take remember this when picking a new boiler.

photo of combi boiler hot water goes cold
low water pressure causing combi boiler to give cold water to shower

 If you are still in the planning stages of purchasing a boiler, consider your flow rate to ensure that a combi is the best option for you.

How to check water pressure

The most accurate way to measure water pressure is using a mains water pressure gauge showing bars.  Follow these steps:

  1. Turn off all taps, inside and outside in the property.
  2. Attach the gauge to the washing machine or dishwasher cold pipe, or sink taps (as instructed by brand manufacturer).
  3. Turn on tap to full.
  4. Check and make note of reading in bars.

How to increase water pressure with a combi boiler system

Install a booster pump

A quick way to increase water pressure in the house is to install a water pressure booster pump. You put it onto the cold water feed pipe and it will increase water pressure to 12 litres/min, which is satisfactory for an improved performance from the combi boiler.

If you aren’t confident to install it yourself, call a plumber who will check it will work in your property.

Clear blockages

Clogs don’t just form beneath drains. They can also form deep within your piping, and even a minor clog can block the system enough to reduce water pressure.

Start with clearing the aerators of sink faucets and taps of blockages.  Once you have confirmed they are cleared, you may need a plumber to fix other blockages in the house.

image of a kitchen sink faucet
Chrome faucet

Fully open the main water valve

image of a stop tap for mains water pipe

Check the stop tap (also known as the shut off valve) is fully open (turn anti-clockwise to open). Even a partial closure will result in a reduction in water pressure.

Check which taps are affected

Check if it affects all cold water taps in your property or just one.  It will be an internal plumbing issue if only one tap is affected.  Call a local plumber for internal problems that you can’t see.

Look for leaks around the house

Stains on the ceiling or walls may give a clue.  Look for pools of water or damp patches on your floor if there are no visible signs of a ceiling leak.

Smells are also a dead giveaway – underground leaks take longer to emerge, resulting in mould and mildew, both of which have a distinct odour.

To help with finding leaks, use leak detecting devices such as this water leak detector from Resideo, around known trouble spots in the home.  It  monitors humidity and temperature with sensors placed at certain places.

image of water stains on ceiling due to leak
leak stains on ceiling

Ask neighbours if they are affected 

It may be a local area issue rather than anything inside your home.  So, if you are not on a joint supply, ask your neighbours if they are having the same problem. 

Water pressure can get low during peak demand such as in the morning when people are getting ready to get to work.

Contact your local water authority

Check if there has been a leak on the mains.  Low water pressure is commonly caused by a lack of water supply during prolonged dry periods or inadequate pumping facilities.

Here’s the list of the UK’s water companies to contact.

Most powerful shower for a combi boiler

Electric shower systems provide consistent water pressure and work well when combined with a combi-boiler.  You will need purpose wiring for the electric shower so add this to the cost.

Electric showers will be the most powerful option when combined with a combi boiler.  It doesn’t rely on the combi for its hot water.

The thermostatic mixer shower is also regarded as a good option for use with a combi boiler. If someone else in your household tries to use hot water while you’re showering, the mixer shower will regulate and control any changes in water temperature.

As a result, the thermostatic mixer shower like this one, is an ideal companion for the combi boiler. Combi boilers can produce a limited amount of hot water at a time; the thermostatic mixer handles this issue by maintaining a consistent water temperature at your desired temperature.

image of low shower pressure

Fitting a mixer shower with a combi boiler

Mixer showers are compatible with combi boilers. These models connect to both your hot and cold water supplies and provide water at the desired temperature.

Because they require hot water from your boiler and the combi has limited capacity, they may not deliver the pressure you desire, especially if other showers or taps are in use.

Best combi boiler for low water pressure

Incoming mains water pressure has to be a minimum level, usually 1 bar. 

So, boiler manufacturers being aware of this, make their products being capable of working at this pressure so looking at only low water pressure, all combi boilers will work fine.  There is no best one in particular.

Will a combi increase hot water pressure?

A combi boiler generally limits the options for increasing water pressure.  But choosing a powerful combi boiler will help in increasing pressure to the shower. 

You will get a better performance by checking there are no blockages or leaks in the pipework going to the shower.  Also, keep boiler pressure to its recommended level.

Can you increase pressure in a power shower?

It is generally not recommended to increase the pressure in a power shower if you have a combi boiler. Combi boilers are designed to provide hot water on demand and do not have a separate hot water storage tank like a traditional boiler.

If you try to increase the pressure in a power shower connected to a combi boiler, it could potentially cause the water to become too hot or put too much strain on the boiler, leading to potential damage or malfunction.

It is best to consult with a professional plumber or the manufacturer of your combi boiler to determine the appropriate pressure settings for your shower.

Can you fit a shower pump to a combi boiler?

You cannot fit a shower pump to a combi boiler system for a few reasons:  many shower pumps cannot handle mains pressure and there is no tank anywhere on the system to draw hot water from. 

Also, the pump will demand more hot water from the combi than it can possibly heat up, leading to cold water at the shower.

What type of boiler is best for low water pressure?

Conventional boilers, also known as regular boilers, are the best type for low water pressure areas.  This is because they have a cold water storage tank in the loft ready to supply the boiler and can then store the hot water in a cylinder.

A combi boiler that does not have constant water pressure will not be as efficient as it could be. It will heat up the water it gets from the mains, but will be able to send out less amounts of hot water due to the low pressure. has boilers for all types of homes and requirements.  Our recommended page explains why you should choose them when looking to install a new boiler.

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*The information in this article should be used for general guidance only and not as financial or health advice.  Full details are on the link in the footer to our disclaimer page.  Always discuss your requirements with a competent and suitably qualified professional before undertaking any work.