Water Pressure Guide

by Greg Dallamore
When choosing taps and showers, it is crucial that you make sure they are compatible with your home's water pressure. In this guide we look at what water pressure is, how to tell what water pressure you have and how it impacts the products you can select for your bathroom.

Water pressure guide

What is water pressure?

Water pressure is simply the pressure at which water flows through your home's pipes and plumbing. Water pressure is measured in bar, the lower the rating the lower the pressure and vice-versa. Typically a domestic household will have a pressure ranging from a minimum of 0.1 bar (very low pressure) up to a maximum of around 3.0 bar pressure (high pressure). All taps and showers have a minimum bar rating that determines what sort of water system they are suitable for. 

What makes water pressure so important is that if you put a shower or tap that requires high pressure onto a low pressure water system, it will not work properly and you will probably get a disappointing flow from it. Conversely if you put a low pressure shower or tap onto a high pressure system, it will still work well - so a low pressure system limits your options whereas a high pressure system gives you a much wider choice of products from which you can choose.

Water system types

The type of water system you have will largely predetermine what sort of water pressure you will have. In the UK, there are three main types of water systems that we tend to use - traditional gravity fed systems, combi-boiler systems and unvented systems (such as a Megaflo).

Gravity systems

A gravity fed system is what was typically installed in the UK until recently. In a gravity system you would normally have a cold water storage tank in the loft and a hot water cylinder elsewhere (such as an airing cupboard). As the name implies, water circulates through the system using gravity which normally results in a low pressure water system. Each meter distance from the tank will result in +0.1 bar pressure, so a 2m drop gives 0.2 bar pressure, a 5m distance provides 0.5 bar pressure. So the further the fall from the tank to your shower or tap, the greater the pressure will be, meaning that often water pressure is better downstairs than upstairs. 

Gravity fed water system

A common solution to improving low water pressure on a gravity fed system is to fit a pump. A pump allows you to increase the water pressure to a higher pressure rating and they are available in various levels of pressure (bar) to suit your household requirements.

So if you have a gravity fed system, you will likely have a low pressure system and will require low pressure showers and taps. If you have a pumped gravity fed system it will be a high pressure system (the bar rating will depend on the model of pump) and you can have high or low pressure showers and taps (provided the minimum water pressure rating is met).

Combi boilers

A combination boiler (combi for short) is a more modern type of system that controls your hot and cold water supply as well as your central heating system (hence the name combination). Combi boilers take water in directly from the mains and heat the water as it comes through on demand (such as when you turn a hot tap on). This means there is no separate hot water tank and often a combi-boiler is located in the kitchen (or wherever is closest to the mains water feed).

Combination boiler water system

As water comes in from the mains, it is pressurised meaning that you have a high pressure water system. Most combi-boilers have some sort of display or gauge that displays the bar rating of pressure that is being achieved. Typically this is between 1 and 2 bar pressure meaning that the vast majority of showers and taps are available to you (provided the minimum bar pressure is being met)

Unvented systems (Megaflows)

An unvented system (often referred to as a Megaflo, which is a brand name) takes cold water in from the mains and then uses a separate heat source to heat the water. In an indirect unvented system water is typically heated by a separate boiler whereas in a direct unvented system the water is heated by an internal element such as an immersion.

Unvented water system, such as a Megaflo

An unvented system therefore provides hot and cold water at high pressure, typically up to 3 bar pressure, allowing you the widest choice of showers and taps available. Not only do unvented systems provide great water pressure, they tend to take up less space as you do not need a large cold water tank and are often quieter than gravity systems and combi boilers.

What showers and taps can I buy?

So whilst water pressure can seem a bit complicated at first, it is actually quite straightforward once you have identified what sort of water system you have. If you have a gravity fed system you will almost certainly have low pressure. If you have a pumped gravity system, a combi boiler or an unvented system you will have high pressure and should be able to see what bar pressure your system is creating from a display or gauge somewhere.

Low pressure systems - can only take low pressure showers and taps

High pressure systems - can take high or low pressure showers and taps (provided the minimum bar rating is met)

If you are unsure on what system you have, or what pressure your system is producing, we recommend that you request that a plumber has a look for you to make sure.