How to Increase Water Pressure in a Shower with a Combi Boiler

Showering should be a completely stress-free experience. On top of keeping you clean, you might also shower to wash away the worries of the day, relax, and unwind. You don't want anything to disrupt that, including low water pressure.

If you're experiencing low water pressure and you have a combi boiler, you're in the right place. We put this guide together to explain why your electric shower might have low water pressure, whether your combi boiler is to blame, and what you can do to increase the flow of water. 

What are combi boilers?

Combination (or combi) boilers combine a water heater and central heating boiler in one compact casing. This means they provide both hot water and heating directly from the main water supply. Gas combi boilers are by far the most common boilers in the UK.

We have a comprehensive guide on what a combi boiler is and exactly how they work here if you'd like to know more.

Why can showers have low water pressure?

There are several reasons you might be experiencing low water pressure in your shower, ranging from blocked shower heads or accidentally shut-off valves to more serious problems, like blocked pipes or a leak. Low water pressure can also be due to a combination of these problems.

1. Mains pressure

If you have a combi boiler system, the most common reason for low water pressure (if it hasn't occurred suddenly after months or years of having high water pressure) is your main water pressure being low.

Your appliances heat water directly from the mains water supply and deliver it to your shower at the same pressure. If you have strong water pressure in your home and there isn’t too much demand for hot water, they can provide the powerful showers you want.

However, if your mains water pressure is low or you have multiple taps and showers running from your boiler at the same time, the flow of water will suffer.

2. Clogged shower heads

If your shower is the only outlet encountering water pressure issues, it could be because your shower head is clogged. This happens particularly in hard water areas where limescale can build up in the nozzles and stop the water getting through. You’ll find products in your local supermarket that will dissolve limescale, so you won't always need to contact a plumber.

Alternatively, if you have had your shower head for a long time, it may be completely blocked. If this is the case, it probably means it’s time for a new one. 

Browse Plumbnation’s range of shower heads and buy online for express delivery across the UK.

3. Leaks anywhere in your home’s plumbing

Any time there is a leak in your pipes, it will cause your water pressure to decline because the water is draining out and not reaching your shower. If you notice a sudden, drastic decrease in water pressure from just one or two appliances, check for leaks. Walk around the house and listen for bubbles, hisses, or drips in the walls. There may also be damp patches or visible puddles.

Even if your water pressure has been low for a while, it could be a sign of a smaller leak.

4. Corroding pipes

If you live in an older house with iron, copper, or steel pipes you might experience a form of corrosion that doesn't happen with PVC pipes. Corrosion occurs when minerals in the water react with the materials of your pipe and produce a gunky, rock-like substance, which builds up inside of the pipes and reduces their diameters. The restricted water flow results in low pressure. 

How to increase the water pressure in a shower with a combi boiler

1. Choose a powerful combi boiler

Choosing a powerful combi boiler with a good flow rate (at least 12-15 litres per minute) will help you to optimise hot water pressure around your home. The flow rate refers to how much water can pass through your appliance in a given amount of time to feed taps and showers.

It's worth noting, however, that if your boiler's maximum flow rate exceeds your mains water supply, your new appliance won't be able to reach its full potential.

2. Avoid using taps while the shower is in use

You might find that water flow is weak when other showers or taps are being used, or that your shower suddenly runs too cold or hot. If you're living with others, it's best to make sure nobody's doing the washing up or using a different shower if you're wanting to take a shower, as the increased demand will cause the water pressure to fall.

If your low water pressure is part of a wider problem in your area, your options are slightly limited when it comes to increasing water pressure with a combi boiler, but there are a couple of steps you can take:

  • Get in touch with your local water provider, who can offer guidance on the next steps and send out an engineer to investigate your boiler and pipes if necessary. 
  • Another option might be to get a flow restrictor fitted to your shower. This pushes the water supply through a smaller space and increases the pressure as a result. A bonus benefit of this is that it helps you use less water when showering because it reduces the flow rate from 12 to 8 litres per minute.

When is it time to call a plumber?

If your water pressure has suddenly dropped and nobody is using other taps or showers at the same time the shower's running, you may be encountering a different issue to the common water pressure combi boiler issues.

You can check whether there are problems that may be affecting the water pressure in your area by contacting the water provider in your area: 

  • Anglian Water – East of England
  • Dŵr Cymru – Wales and parts of western England that border Wales
  • Hafren Dyfrdwy – North East and mid Wales
  • Northumbrian Water – Northumberland, Tyne and Wear, Durham, and parts of North Yorkshire
  • Severn Trent Water – Midlands and Wales
  • South West Water – Devon, Cornwall, and small areas of Dorset and Somerset
  • Southern Water – Hampshire, the Isle of Wight, West Sussex, East Sussex, and Kent
  • Thames Water – Most of Greater London, Luton, the Thames Valley, Surrey, Gloucestershire, north Wiltshire, and far west Kent.
  • United Utilities –  North West England
  • Wessex Water –  Bristol, most of Dorset, Somerset and Wiltshire, and parts of Gloucestershire and Hampshire.
  • Yorkshire Water – West Yorkshire, South Yorkshire, the East Riding of Yorkshire, part of North Lincolnshire, most of North Yorkshire, and part of Derbyshire.

If your area isn’t experiencing water pressure problems, then it’s likely one of the household issues mentioned, whether that’s your mains pressure, a clogged shower head, a leak, or corroding pipes.

Calling a plumber for a clogged shower head

If you’ve tried unclogging your shower head using limescale dissolvants but are still experiencing difficulties then it might be time to contact a professional plumber for support. They will be able to take your shower head and hose apart and inspect for any blockages.

If you’ve decided to replace an old shower unit, but would rather let a professional install it, your plumber can do that quickly and easily.

Calling a plumber in the event of a leak

If you think a leak is why you're losing pressure, but it isn’t coming from an easy-to-reach place or you don’t feel confident patching it yourself, you should contact a professional plumber who'll take a look for you.

In the meantime, in order to keep the puddle from growing, it’s a good idea to stop the water supply to the boiler. You can do that by turning off the internal stop tap. The stop tap is a spoutless tap or lever that sits between two lengths of pipe acting as a connector. It’s usually located under your kitchen sink, but can also be found in your kitchen cupboard, downstairs bathroom or toilet, garage or utility room, cellar, or under the stairs.

Calling a plumber about corroding pipes

If you have noticed any corrosion in your pipes, you should ask a plumber to investigate the problem before it becomes more serious, or you can end up with more expensive damage on your hands.

If you spot signs of corroded pipes, your plumber can tackle pipe replacement or cleaning before things get worse.

Find a top-quality shower or combi boiler with Plumbnation

If you think it might be time to buy a new shower or invest in a more powerful combi boiler to increase your water pressure, look no further. Here at Plumbnation, we stock the highest quality appliances at affordable prices.

FAQs about combi boiler water pressure

Do y​​ou get good water pressure with a combi boiler?

If you have a combi boiler, the cold water coming into your house will be at mains pressure, which should usually be at a nice, high pressure. They can struggle if there's more than one shower running at one time, though, due to their compact size.

Can I have a combi boiler if my water pressure is low?

All combi boilers have a minimum working pressure, below which they will not function correctly. If the mains water pressure is too low, the minimum operating pressure for a combi boiler won't be achieved and can stop the boiler from firing, give you poor hot water delivery, or hot water delivery will come and go.

If you believe your water company isn't providing you with sufficient water pressure, contact an expert. The Water Services Regulation Authority (Ofwat) guarantees the minimum standard of service from your local water company, so you might be entitled to compensation.

Can you use a shower pump with a combi boiler?

Unfortunately no, you can't use a shower pump with a combi boiler to increase water pressure. Shower pumps are connected to hot water cylinders, which is a feature that combi boiler heating systems lack.

This is because many shower pumps can’t handle mains pressure and there’s 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 heat up, leading to cold water at the shower.

What types of showers have the best water pressure?

If you have a combi boiler, the water pressure will usually be high and a mixer shower should work well. On the other hand, if you have low water pressure, an electric shower might be a better option for you.

We have a guide that takes every possible factor into consideration when choosing the right shower for you and your home.