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Understanding Water Pressure

WHAT IS WATER PRESSURE?

Water pressure is a measurement of how quickly the water flows through the mains, into your pipework and ultimately out of your taps or shower.

Pressure is measured in bars - the base measure is 1 bar. One bar of force is required to push water to a height of 10 metres.

Water pressure can vary greatly from home to home, room to room and even different times of the day depending on who is using the water in the home.

All taps and showers are rated with minimum pressure ratings which will usually be between 0.1 and 3 bars. Anything below one bar is considered low pressure.

Your water supplier has to, by law, supply a minimum of one bar of normal mains water pressure to your home but the pressure will depend upon where you home lies in relation to the nearest supply/reservoir. Even the height of your home can impact your water pressure - if you live at the top of a hill, you will have lower water pressure than someone who lives at the bottom of a valley as the water flow has to work against gravity to get uphill.

The time of day can affect the demand for water and in turn negatively impact your water pressure regardless of whether you have high or low pressure. You may find that your water pressure is worse in the early morning when people are getting ready for school or work and that it improves late at night when the demand from your water service provider decreases as most people have their taps turned off. The weather can also play a role - during the summer months people are often watering their gardens or filling up a paddling pool which may also mean a lack of pressure.

WATER PRESSURE VS WATER FLOW - WHAT IS THE DIFFERENCE?

When discussing water pressure it's important not to confuse it with water flow. Put simply, water pressure is a measure of force and water flow is a measure of volume - water flow is measured in litres per minute. Despite the difference in definition, your water flow can be a good indicator of how good or bad your water pressure is.

An easy way to measure your water flow rate is to get yourself a jug (between 1-2 litres in size is preferable) and a stopwatch. Put your jug under your tap, turn it on and run it for 6 seconds. When the time is up turn off the tap and check how much water is in your jug. Now for a quick bit of maths!

Take the amount of water in your jug (in litres) and multiply it by 10. For example, 0.6 litres x 10 = 6 litres per minute. This is your property's flow rate in litres per minute. If the flow is less than 10 litres per minute, you have low water pressure. A flow rate between 10-15 litres per minute would be considered acceptable but can still be improved. Anything above 15 litres per minute would be considered good or high water pressure.

WHAT TYPE OF WATER PRESSURE SYSTEM DO I HAVE?

GRAVITY FED

By far the most common hot water system in the UK and standard in older properties is a gravity fed system.

As the name suggests, a gravity fed water system relies on gravity to deliver water around your home. You will know if you have this system if you have a cold water tank (cistern) in your loft and hot water tank (cylinder) normally in your airing cupboard. The pump hauls the water up to the roof from the mains supply and then the tank releases water through outlets in its base.

With gravity fed water systems, the higher the vertical distance between the tank and the tap, the higher the pressure - so taps on the ground floor often flow faster than those higher up. Typically, you gain about 0.1 bar of water pressure per metre of elevation.

Your choice of tap might be limited if you have a gravity fed system. You will be able to install a mixer, pumped digital or all-in-one power shower and get a great showering experience. Assuming you decide on a mixer and want a more forceful shower, fitting a pump will boost the flow rate and pressure even further.

UNVENTED WATER SYSTEM

If you have a hot water tank but no cold water tank, you have an unvented water system (sometimes called a Megaflo system). The water in the main cylinder is kept under constant pressure by incoming mains water and then heated from an external source - a boiler, oil, electricity or solar panels. With no requirement for a header tank, it makes this an ideal water system for when you don't have loft space.

It is important to note that, despite the advantages, an unvented cylinder is a pressure vessel storing large volumes of heated water. If it is installed incorrectly, is tampered with or the temperature/pressure gets too high the possibility of explosion is very real. For this reason the installation of unvented hot water cylinders is governed under G3 Building Regulations.

COMBI-BOILER

A combination boiler is usually located in your kitchen at the point where the pressurised cold mains water enters your property. It manages both your hot and cold water supply as well as your central heating, hence the name combination - you will not have a separate cold or hot storage tank. It heats water directly from the mains supply giving you hot water on demand.

As your water supply comes from the mains, at mains pressure, you will have high water pressure suitable for the majority of taps and showers - provided you have a good combi-boiler. Combi-boiler pressure is usually somewhere between 1 and 2 Bar. For a powerful showering experience you can fit a mixer or digital shower to this system.

WHY IS MY WATER PRESSURE LOW?

We have already discussed a few reasons why your water pressure might be on the low side but there are a number of other reasons why it might be happening:

• Narrow pipes - Older properties were generally built with narrower pipes than our modern homes (the pipes in new builds can be twice as wide). This can cause low pressure problems especially if you are trying to run multiple appliances at the same time.

• Blocked pipes - In the same way that a blocked drain can make your sinks slow to drain, a blocked pipe can impact your water pressure through rust, dirt or limescale.

• Clogged taps/shower - As with your pipes, limescale can build up in your taps and shower (particularly in hard water areas). Many showers have a filter to protect them from debris that might be in the pipework but this can become blocked too. If you find that your tap and shower are running at different rates, this might be the cause.

• Shower height - There needs to be a minimum height of 1 metre between the shower head and the water level in your property's water tank for showers to perform at their best. The higher the shower head, the greater the water pressure.

• Leaks - Even small leaks can cause of loss of pressure from your system. If you have a water meter you can check for leaks by not using any water in the house, make sure all taps and appliances that use water are off. Check the water meter - if it is still spinning then water is being used somewhere. The next step would be to shut off the water mains supply to you home and check the water meter again. If it is spinning again then it could indicate a leak.

IMPROVING WATER PRESSURE

For most people, their water pressure doesn't pose a problem with tasks like washing their hands, brushing their teeth or doing the dishes but it becomes more of an issue when wanting to take a decent shower or filling the bath.

If you have your heart set on a top of the range power shower but your water pressure isn't good enough to make it work properly then you have a few options.

Firstly, you can improve your pressure by raising up your cold water storage tank but this might be too expensive of an option or you might not have a cold water tank so you could try swapping out your shower head to one that has been designed to work with low pressure.

The other alternative is to install a shower pump to use with your new shower. A shower pump is designed to pump more water through your shower head to give a more powerful showering experience. Be aware that pumps can be costly and make noise and they cannot solve low water pressure coming from the mains.

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