Water pressure and flow

Especially in cities but also in rural properties it can be difficult for the cold water main to meet the demand for hot and cold water supply.

Traditionally all hot and cold water outlets were supplied from a storage tank in the loft. Now it is increasingly common for everything to be mains fed.

Whether hot water is heated directly with a combination boiler or indirectly and stored in an unvented cylinder, the majority of new systems rely on mains pressure to drive all outlets.

This requirement can lead to several issues in the home. 

1, Small bore.  A lot of properties have small lead or copper pipes feeding from the shared main in the road.  Although this doesn't affect the static pressure it does prevent sustained flow due to a bottleneck effect.  In this instance replacing the underground pipe can make a significant difference but there is no guarantee.

2, Shared main. Many properties but mainly flats have a shared mains pipe, this was adequate when they were feeding tanks but inadequate now most appliances are mains fed. Whenever there is a high demand period like early mornings or late afternoons.

3, Dense population. More and more we are living in close conditions. Where a house used to have just a single family of maybe four people, it is quite common for that to have been split into two or more flats with twice the people. The mains pipe was designed at a time when the demand hadn't been anticipated.

So what can be done?

Ideally the water companies would simply turn up the pressure and install a water meter. The more you use, the better.

Unfortunately this isn't always possible. The older supply pipes under the roads may have small leaks or be of a construction that can't cope with a higher pressure.

There are many products on the market that address the issues of insignificant water pressure and flow.

Header tanks - sometimes simply adding an old fashioned header tank can be the most cost effective way to maintain flow to multiple outlets.  Although not as clean due to the stored water and only gravitational pressure it is a quick and easy remedy.

Buffer tank and pump - Essentially a header tank with a pump downstream, the split design allows for the tank to be installed remotely and the pump in a serviceable area.  This gives great pressure and as long as the tank is sized correctly for the property and there is no interruption in electricity it is a very reliable system.

All in one booster - Systems made by Grundfos and Lowara incorporate a small reservoir of water and a large domestic pump.  This can have its drawbacks as the reservoir is limited and depending on the incoming replenishment rate could run down and leave you without anything for a short time.  They also rely on mains electricity so if there is a power cut the homeowner will need to turn on the bypass (if it has been installed correctly) or else they will have no running water.

Accumulators - These are large cylindrical expansion vessels that absorb pressurised water during the periods of low demand.  The internal air charged bladder allows the water in to the reservoir and stores it there until the pressure in the property is less and upwards of a couple of hundred litres of water can be available.  There are a few U.K distributors of accumulator, they used to be all steel construction but Great water now have a composite model in the Provess which is lighter, easier to install and will last longer.  The accumulator requires no electrical supply so will work without power and even if there is a water cut and power cut will provide water for a good few showers before running out.

Accumulator and booster sets - The best sealed solution is one or more accumulators with a priming pump.  The pump monitors the pressure between it and the accumulator and switches on to increase the pressure and stored volume.  The accumulator absorbs the pressure up to around 6 bar and ensures all outlets have sufficient pressure and flow.  Although the pump requires electricity to run the accumulator will still work in a power cut.  This system takes a fair amount of space but is quite quiet and reliable.