Serving parts of North West London and the Home Counties.


Low Water Pressure


Water pressure is the amount of force that the water moves through the pipework. The pressure is measured in ‘bars’, and one bar of pressure is required to lift water by 10 meters.

Water pressure does not remain constant and can vary when demand for water is high. For example, during busy morning and evening periods or in hot weather, water pressure in the mains network may reduce.

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 such as a burst water main.

Water pressure is measured at the point where it leaves our pipework at the boundary stop tap and flows through your supply pipe. All water companies are legally required to supply a minimum water pressure of 0.7 bar to the point that their pipework meets the homeowner's supply pipe. In most cases, this is indicated by a boundary stop tap at the property.

Other factors that can affect the water pressure in your home include the plumbing inside the property and shared supply pipes.

Your water supply enters your home via the internal stop tap, and your cold kitchen tap should be supplied directly from our mains supply.

Any reduction in pressure from any taps inside your home, which does not affect the cold kitchen tap, could be caused by plumbing issues with your water pipes. Properties that have a shared supply are more likely to experience low water flow rates.

If you are not on a shared supply, your neighbours should have the same water pressure as you, providing your houses are of very similar height and the same distance from our water main.

The only way to formally measure your water pressure is by using a water pressure gauge.


Low Water Flow

Water flow is the amount of water that passes a valve or tap per minute. You can measure your water flow at home using a 1 litre jug and a stopwatch. Place the jug under the tap and using the stopwatch to time 6 seconds before turning off the tap, then measure the amount of water in the jug in litres (e.g. 0.9L) and multiply this by 10 to calculate the flow rate in your property (e.g. 9 litres per minute). This test is only accurate for properties that are not sharing a supply pipe.

Low water flow is frequently mistaken for low water pressure at your tap or shower as it is possible to have a low flow with high pressure.

The pressure within the water main will deliver the same water pressure for all houses in a street that it is connected to it (give or take any differences in ground level; 1 m of additional elevation would equal a drop in pressure of 0.1 bar).

We aim to provide as a minimum the legal level of water flow of 9 litres per minute.

The flow of water to your property will be dependent on the condition of your private supply pipe. If your supply pipe is in poor condition, the amount of water the pipe carries could be restricted and therefore reduce the flow of water to your taps. This can be caused by;

  • the diameter of the pipe

  • corrosion in the pipes and/or on appliances, iron pipes in particular, can suffer extensive corrosion

  • the demand for water in your home at a certain 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 etc.

  • Any inconsistencies in the pipe, e.g. a stop tap that is partly shut, grit obstructing a ferrule, a meter, damage, internal corrosion.




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, then it is worth checking 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, as can the condition of your pipes. 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 any new appliance (heating system, shower etc.) please make sure to check with your water industry approved plumber that your new appliance will work at our minimum target of 0.7 bar of pressure. It is worthwhile to check that 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.

Some insurance companies will inspect the internal stop taps if you have an internal leak and need to make a claim. Its good practice to know where yours is and ensure its maintained and working at all times.

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How a tank system is set up within the homeHomes 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 is 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 also affect the water pressure to the taps.

We are legally required to supply a water pressure of 0.7 bar to your outside stop tap. Pressure is measured in bars, and 1 bar will push the 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. If you wish to fit a pump, please contact our network regulation team please email

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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 0.7 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 0.7 bar for them to run effectively. If your plumber has assessed the water pressure inside your property to be below 0.7 bar, it is possible 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, the flow rate at your cold water taps may reduce if they are run at the same time as a hot tap.

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Megaflow Boiler Systems

Megaflows are systems that store hot water and dispense it at high pressure when required.

These are often installed in properties that are particularly large or have multiple bathrooms. Installing a Megaflow will likely require your supply pipe to be upgraded for a larger diameter to increase the flow of water to the Megaflow.

Megaflows are directly fed from the water mains instead of a 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 demand particularly during the busier times such as mornings, early evening and during the summer. High demand can reduce the water pressure in our water mains network.

Megaflows require a minimum water flow to work. Before having one fitted check that your internal pipework and supply pipe are capable of delivering 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 0.7 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 0.7 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. This can be resolved by increasing the size of your water supply pipe. 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 may be able to 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.



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.


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.



Leaks from pipes or fittings will reduce the water pressure. If you have a water meter you can check if you have a leak and may be able to locate it using the following check:

- Stop using water inside the property (Washing machines etc.) but do not isolate the supply at the internal stop tap. Now check if the meter is spinning. If so then there is water being used somewhere along the pipework from your meter into the house. Now try the below to identify if this is a possible supply pipe leak or internal leak.

-Turn off all the water in your home using the internal stop tap and check if the water meter is still spinning. If the water meter is spinning and your internal stop tap was successful in isolating the water inside the house, this would indicate a possible leak on your private supply pipe outside the property.

-If the water meter stops spinning and starts again when you turn the internal stop tap back on. This would indicate either a constant water use inside the property (Tank filling etc.) or a possible leak inside the property itself at some point after the internal stop tap

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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 0.7 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 or if all properties on the same supply pipe 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 boundary stop tap.

If you are on a shared supply and would like to have your own water supply, please contact our Developer Services department to investigate if a separate supply 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 0.7 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 device 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

If you are considering installing a booster pump, please contact our network regulations team for advice; email

Pumps that are capable of pumping more than 12 litres per minute are Notifiable to us by law, and failure to do so could lead to prosecution with a fine up to £1000 and a criminal record, even if the amount they pump is variable. Please use our online form to notify us >>

Do not fit any pump on your supply pipe if you are on a joint supply with 1 or more neighbours as this can cause your neighbours low flow problems and could cause contamination of your supply, your neighbours supply, and intern our networks; this again could lead to criminal prosecution.

In blocks of flats booster pumps are used to boost water to the flats this is done indirectly from the mains supply, via a storage cistern that stores the water to be boosted. If you live in a flat and have noticed a change in your water pressure after a power cut or interruption to your water supply, then your booster pump may need resetting. Please contact your landlord or managing agent to reset the pump. This is not a job we can do.


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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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