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water pressure in watford

Boilers Explained - Water Flow and Pressure

Thursday 19 May, 2016

Listen to our podcast on this subject.

We have found that within the Watford and Hertfordshire area, more and more homes are either fitting combination boilers or unvented hot water cylinders. These all rely on mains flow and pressure to work effectively. As a result the industry is having to find new solutions to the issue of low water pressure and flow.

There are several reasons for a lack of flow or pressure these are:

  • Insufficient mains supply to the property
  • Usage from surrounding properties in peak times
  • Pipe sizing within the property leading to a lack of supply when multiple outlets are used at the same time

The problem is being exacerbated by modern sanitary ware being designed to work with high-pressure systems. This means that taps don’t work well, toilets take a long time to refill and showers run slowly.

One of the first things to understand is the difference between pressure and flow.

Water pressure is the force with which the water arrives at your home. This is measured in bar pressure with 1 bar being equivalent to a tank of water being 10 meters above the outlet. The water board have a target to provide at least 1 bar pressure but the majority of bathroom fitting now require more than this, with some requiring up to 3 bar of pressure to work efficiently.

Water flow is the amount of water that comes out of the pipes in a set period of time. This is measured in litres per minute. The water board have a target to provide 9 litres a minute but again most modern showers need at least 9 litres a minute so if you want to run more than one outlet you will need to increase the flow.

Below are a couple of ways to overcome these issues and get the water system that you want within your home.

Mains booster pumps

These are specifically designed to be fitted directly to the mains and used to boost the pressure and flow. This could enable a house to fit an electric shower or combi boiler where it couldn’t before. A mains booster pump is relatively inexpensive to supply and fit, but will only bring the supply up to a maximum of 3 bar, and 12 litres per minute. This would mean you could run one good shower, but it would be effected by a second outlet being used at the same time.


An accumulator is a tank that is fitted to the cold water supply pipe. Accumulators are generally used in conjunction with an unvented hot water cylinder, but can be used in a variety of situations where the pressure or flow is either inadequate or inconsistent. They work by storing pressurised water and then releasing this water when the incoming mains cannot maintain supply. The size of an accumulator depends on the system you have in place. However, they can be a sizable tank, so siting the accumulator must be considered carefully before going for this option. It will however let you run multiple outlets without a drop in performance. The plumbing of the accumulators is a relatively simple task and so should not add to much cost to the works but the benefits gained can be significant and can far outperform the booster pumps.

For more informatin on the different types of boilers check out our ' Boilers Explained' blog. 

At Ben Guest Services we can test your water flow and pressure and make recommendations should pressure be low. We cover the Watford, Bushey, Croxley Green and Rickmansworth areas in Hertfordshire and would be happy to provide a free assesment at your home. 

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