Water Pressure Explained

Water pressure can be described as the force that water is pushed through a pipe.  The higher the water pressure the more it will flow through the pipe and the faster it will come out of a tap.

The amount of pressure is dependent on the following factors:

1. The height of the reservoir/water tower in relation to your property – the higher the better
2. The height of your property in relation to the reservoir/water tower – houses at the top of a hill will have lower pressure than those at the bottom of the hill.

Sometimes the water pressure can be too low.  This can result in the water running very slowly making it take a long time to fill up a bath or even a kettle in some cases.  Low pressure can also affect the functionality of some appliances such as water heaters or showers.  The main reasons water pressure can be too low are:

1. The demand for water at different times of the day – water pressure can be lower during peak times such as in the mornings or early evening.
2. Water pressure can be lower during long dry spells, when demand is high due to the use of hosepipes and sprinklers to water gardens.
3. Water pressure can be lower when there are inadequate pumping facilities on the distribution network.
4. Water pressure can be lower when the water mains are too small.
5. Water pressure can be lower due to leaks, distribution equipment failures and blockages in the pipe work that distribute the water.

Sometimes the water pressure can be too high.  This can damage plumbing fixtures and fittings, which in turn can lead to flooding.  The main reasons water pressure can be too high are:

1. Sometimes air can get trapped in the pipes, which can lead to a temporary build up of water pressure.  This can be resolved by running the taps in the property for a while to release the pressure.
2. It is sometimes necessary to re-route the water supply which can result in high pressures.  This is usually only a temporary situation, and the normal supply is returned, and the pressure resumes to normal.

There are official standards of water pressure that the water companies must comply with.  This sets out a minimum water pressure that they must maintain.  Water pressure is measured in:

1. Bar – This is the most common parameter and can be calculated to be 1 Bar is equivalent to the force required to push water up 10m.  The average water pressure in the UK is between 2 and 4 Bar.
2. PSI – Pounds per square inch.  This can also be used to measure the water pressure in a property. 1 Bar is equivalent to 14.5 PSI
3. MPa – Megapascal. One megapascal is equal to one million pascals. This is normally used to measure higher pressures in systems such as hydraulics, however it is sometimes used in describing water pressure, so worth a mention. 1 Bar is equivalent to 0.1 Megapascal.

The effect of fitting an appliance or equipment in a pipe on the water pressure.

In general fitting something into the pipework of a property should not have a significant affect on the water pressure. This is based on the Bernoulli’s law and the venturi effect, and we will leave you to check this out if you want to know more!

Our lab tests have shown that when using a pressure gauge on a tap that has nothing connected to it, we get a pressure reading of 3.5 bar. When we fit one of our Imrita flow-based water leak detectors between the tap and the pressure gauge using a 1m length of pipe, the reading is still 3.5 bar.