Serving parts of North West London and the Home Counties.

 

 

Low Pressure


 

Low Water Pressure

Water pressure is not constant and demand during busy morning and evening periods may reduce water pressure in the mains network. Low pressure can occur when the pressure in the water main is not enough for water to reach the top of the house. This is very rare and may only happen in the event of an emergency e.g. a burst water main.

No matter what the pressure is in our mains network, the plumbing of the water pipes in your home may substantially reduce that pressure by the time it gets to your taps.

Any reduction in pressure inside your home , which is not affecting the cold kitchen tap could be caused by plumbing issues on your water pipes. Properties that have a shared supply are more likely to experience low water flow.

We are legally required to supply a minimum water pressure of 1 bar to your boundary stop tap. Pressure is measured in bars and 1 bar will push water to a height of 10 metres to your home. Water pressure is measured at the point where it leaves our pipework and flows through your outside stop tap or property boundary.

If you are not on a joint supply, your neighbours should have the same water pressure as you, provided your houses are of very similar height and the same distance from the point where our water main is located. Your water flow is individual to your property and may differ from your neighbours.

 

Low Water Flow

Sometimes low pressure could be confused with low water flow at your tap or shower. It is possible to have a low flow with a high pressure, or a good flow with a low pressure.

The water main pressure will be the same for all houses in a street that it is connected to it (give or take any differences in ground level; 1 meter higher in ground elevation equals 1m less pressure). However, the flow to your property depends on the condition of your private supply pipe.

Your water pipes may be restricting the flow of water to your taps. In other words, the maximum amount of water your pipes can carry will be affected by:

  • the diameter of the pipe

  • corrosion in the pipes and/or on appliances

  • the demand for water in your home at a particular time

  • the length of the supply pipe

  • if you have a leak on your supply pipe

  • The pressure in the water main

  • The number and type of fittings along the pipe e.g. ferrules, stop taps, meter, bends, stop tap etc.

  • Any inconsistencies in the pipe e.g. a stop tap that is partly shut, grit obstructing a ferrule, stop taps or meter, a section of pipe that has been squashed nearly flat, internal corrosion.

 

How to test your water pressure

*please note this is only for properties that have a single supply pipe*

Using the first tap off the supply pipe (usually the kitchen tap)

1. Fill a 4.5 litre (1 gallon) bucket with water

2. Make sure all other taps and appliances using water are turned off.

3. It should take 30 seconds to fill the bucket with water.

If it takes longer to fill then it’s likely you have a water pressure or flow issue. Click here to find out the common causes of water pressure and flow problems to help you track down the issue.

 


 

What could affect your water pressure

 

 

 

Heating appliances and showers

Sometimes installing new appliances like washing machines, dishwashers or power showers can affect your water pressure. If you operated the internal stop tap to install the new appliance, please check it is fully open again.

The layout of the water pipes in your home may reduce the water pressure or water flow to your taps and your shower. Many new showers will need a minimum level of flow and pressure to work effectively, which can vary by manufacturer.

If you are planning to fit a new shower or heating system soon, please make sure you check with your water industry approved plumber that it will work efficiently at our minimum target of 1bar pressure and check your internal pipework will deliver the water flow necessary for the best performance.

If you are planning to carry out some plumbing work in your home, it is a good idea to check that your internal stop tap is working properly so you can turn off the water in an emergency. In many homes, the stop tap can be found in the kitchen, near the sink. For help finding your stop tap watch our how to guide.

Please note: You are required by law to have a working internal stop tap, so you can turn off your water in an emergency.

Once your works are completed please remember to fully open your stop tap, it is surprising how often this can cause an issue.

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Tank SystemHomes with a water tank

The water from our mains flows through your underground supply pipe straight to your kitchen tap. The water then flows to a storage tank, which supplies water to all your taps including the hot water.

Water pressure is lost the higher water has to be lifted, so how high your water tank is positioned above your underground supply pipe will affect how quickly it refills. The position of the tank above the taps will affect the water pressure to the taps.

We are legally required to supply a water pressure of 1 bar to your boundary stop tap. Pressure is measured in bars and 1 bar will push to water to a height of 10 metres to the pipes in your home. If your cold water tank is above this height you may want to consider fitting an internal pump to push the water up to the storage tank in your loft.

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Homes with a combination boiler

The water from our mains flows through your underground supply pipe and the water goes to your combination boiler. The boiler then supplies all the hot taps inside your home. Combination boilers will not work below certain pressure levels.

We are legally required to supply a water pressure of 1 bar to your boundary stop tap. Conventional boilers can run on as little as 0.5 bar, but the pressure for combination boilers may need to be above 1 bar for them to run effectively. If your plumber has assessed the water pressure inside your property to be below 1 bar, it is likely that this is due to the condition of your pipework. Where possible, ask a water industry approved plumber to also assess the pressure at the boundary stop tap. If this is not possible contact us to carry out the check.

Some combination boilers are only capable of supplying water to one hot tap at a time. Also the pressure at your cold water taps may reduce if they are run at the same time as a hot tap.

If you are planning to install a new boiler soon, please make sure you check with a water industry approved plumber that it will work efficiently at our minimum target water pressure of 1 bar and your internal pipework will deliver the water flow necessary for the best performance.

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Megaflows

Megaflows are another system for heating your water and often require an increase to your supply pipe diameter to increase the flow of water to the cylinder. Megaflows operate differently to conventional heating systems because they are directly fed from the water mains instead of the cold water tank, which can make them more sensitive to fluctuations in the mains water pressure.

Water pressure to a property can fluctuate depending on customer demands especially during the busier times such as mornings, early evening and during the summer. High demand may reduce the water pressure in our water mains network.

Megaflows require a minimum water flow to work. If you are considering fitting a Megaflow to your property please check that your internal pipe work and supply pipe are capable of delivery the required water flow. It is advisable to check with a water industry approved plumber first who can tell you if a Megaflow will work in your property and if you need to make any adjustments to your pipework.

We are legally required to supply a water pressure of 1 bar to your boundary stop tap. We cannot guarantee to provide above this level, even if the area you live in historically had higher pressure. If you notice the pressure changing, please reset the controls of the Megaflow closer to the statutory minimum of 1 bar.

Your water flow should not be affected by any works we do on the water network (except in case of an emergency) but Megaflows may require a higher flow rate than you currently have. You can resolve this by increasing the size of your water supply pipe (the pipe which runs from the boundary stop tap to your kitchen tap). We aim to provide as a minimum the legal level of water flow of 9 litres per minute. But if your Megaflow requires more than this we can upgrade our pipework from the water mains to the boundary stop tap, a charge will be applicable.

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Pipes inside your home

 

Some pressure problems can be caused by faulty, damaged or leaking pipes and fittings, like ball values and stop taps.

 

Corrosion

If the pipes in your home are old, they may be corroded, restricting the water flow. You may want to ask a water industry approved plumber to check this for you.

Older properties can have lead pipes from the boundary stop tap to the kitchen tap. Lead can create scale build up in the pipes over time creating a water flow problem. To learn more click here.

 

Stop Tap

A partly closed stop tap inside your home could cause some water pressure problems; gently opening up the tap may increase the pressure.

To fully open the tap:

1. Open and close it several times until the number of turns from open to closed is constant.

2. Do not leave the tap fully open.

3. Turn it back a quarter of a turn to stop it seizing up

 

Some properties can have more than one stop tap and each one can affect your water pressure and flow. Please check that all stop taps are working properly if you are experiencing water pressure and flow problems.

Please note: You are required by law to have a working internal stop tap, so you can turn off your water in an emergency.

 

Leaks

Leaks from pipes or fittings will reduce the water pressure. If you have a water meter you can see if you have a leak by turning off all the water in your home and checking if the water meter is spinning. If the water meter is spinning you may have a leak. For more helps see our step by step guide to check if you have a leak.

If you do not have a meter, listen for hissing sounds from inside pipes or look for damp patches or very obvious green patches on your grass. If you suspect you have a leak inside your home, contact a water industry approved plumber for advice.

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Supply pipe length and size

The water flow and pressure in your home will be affected by the length of your supply pipe. For example longer supply pipes with a small diameter may be too small to deliver the flow of water to your property, even though the pressure at the boundary meets the 1.0 bar target.

If you are considering replacing your pipework, like for like with the same diameter or maybe upgrading to a larger pipe, this is likely to increase the flow of water to your property but will not increase the water pressure to your property.

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Shared supply pipes

Some pressure problems are caused by more than one property sharing a supply pipe from the water main.

This can be a problem if the supply pipe is too small, in poor condition (for example, leaking or old), of if all properties are using the water at the same time (especially at peak times).

If you are on a shared supply with your neighbours, then you are jointly responsible for maintaining and repairing it from your property to the stop tap. (See figure below)

 

If you are on a shared supply and want to separate it and have your own water supply, please contact our Developer Services department to investigate if a separate new independent pipe can be installed from your boundary stop tap. We can advise and support the route your pipework should take, the material and size needed and guide you on ownership of any remaining pipework through your property and provide a quote for the works to take place.

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Geographical location

Water pressure can be affected by the height of your property in relation to the local area around it. If your home is at the top of a hill, you may experience lower pressure than properties that are at the bottom of the hill, especially during busy times of the day such as morning and early evening and during the summer.

We are legally required to supply a minimum water pressure of 1 bar to your boundary stop tap. However, if you feel this does not meet your needs, get advice from a water industry approved plumber on how you can improve your pipework. Your plumber may want to consider installing a water accumulator. This is a relatively new device that holds water in a vessel during those periods when demand for water in your house is low and releases the water as you need it at busy times.

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Booster pumps

Booster pumps are connected to the private supply pipe of flats or to large houses. They help to boost the water around the property.

Booster pumps come in different sizes; domestic pumps will fit underneath your sink and connects to a power source and a larger size will need its own pipework and a dedicated power supply.

In a block of flats booster pumps are normally used to fill large header tanks then the water then flows to each of the flats under gravity from the tank. In a house they help to boost water pressure to a specific point such as the bath (normally connected under the bath).

If you live in a flat and have noticed a change to your water pressure following a power cut or interruption to the water supply, then your booster pump may need resetting. Please contact either your landlord or managing agent to reset the pump. Please note we do not know the locations of booster pumps because they are fitted to private properties.

 

Water pumps

We are legally required to supply a minimum water pressure of 1 bar to your boundary stop tap, but if you feel you need more pressure you may think about fitting a water pump to your home which helps to increase the pressure.

When you are fitting a water pump please use a water industry approved plumber. They can look at your water fittings, water use and internal plumbing to give you advice on what pump is best, and ensure you do not breach any Water Fittings regulations.

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What to do if you still have water pressure issues

If you have done some of the checks mentioned above and still feel there is a water pressure problem, please complete our form and we will respond to you as soon as we can.

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Compensation for low pressure

You are entitled to a payment if we fail to maintain a minimum water pressure on our mains network. If you are affected by low pressure of below 0.7 bar, lasting an hour or more on two separate occasions within 28 days of each other, we will pay you £25 or add this to your account to reduce your bill. We will only make one payment each year.

Please note that this compensation policy does not apply where the cause of the low pressure is due to emergency or planned maintenance work to our mains network.

Unfortunately you will not be able to claim compensation for poor pressure if the problem is caused by your pipes.

To make a claim, this must be in writing within three months of the second incident of low pressure.

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For further helpful advice, visit the Water Regulations Advisory Scheme >>