Help make the best choice when selecting a new shower and taps
Understanding the water pressure system that is installed in your home is important when choosing taps, showers and other plumbing fittings for your home. Match the right tap or shower to your water pressure and you’ll get great performance – mismatch them and you may find that your taps run very slowly, or hot and cold water runs at different flow rates making it hard to strike a comfortable balance.
Water pressure systems are made up of a combination of a boiler (also known as a combi boiler) and water storage tanks. Some homes may not have a boiler (the water will be heated by electrical elements in a tank or other heater) but will have hot and/or cold water tanks, and others will have a boiler but no water tanks.
Which system do you have?
There are three main types of system; gravity fed, combi boiler and unvented.
Gravity fed system
Your cold water tank will be in the loft and a hot water cylinder elsewhere (most likely in an airing cupboard), and these systems are generally found in older properties. This means you have a low pressure water system and you’ll need to choose taps and showers designed to work with lower water pressures.
However, if you have enough height between the bottom of the cold water tank and the tap or shower, it is possible to have high pressure at that particular outlet, and we’ll show you how to measure this later in the article so you can choose the right taps or shower for your pressure.
A gravity fed system will limit your choice of tap, but installing a water pump will increase the pressure and give you access to a wider range of taps and a better shower experience.
Below is an example of an indirect cold water gravity system:
Combi boiler system
Your boiler will be wall-mounted and probably located in your kitchen or hidden away in an airing cupboard. You won’t have a cold or hot water storage tank. This means you have a high pressure vented water system. This system is becoming increasingly popular in the UK and is considered an ideal choice for small apartments and new builds as it gives you hot water on demand.
Combi boilers are fed directly with mains pressure cold water, which is then rapidly heated and pumped around your home at close to mains pressure. High pressure water systems offer the flexibility of being suitable for use with most showers and taps, so you shouldn’t need to calculate your water pressure when buying new taps or a shower.
Pressures can vary depending on your boiler, but the typical pressure expectation is between 1 and 2 bar.
Below is an example of a combi boiler system:
If you have a hot water tank but no cold water tank you will have an unvented water system, providing high pressure.
Water will be stored at mains pressure in a strengthened hot water tank, where it is heated by immersion heaters attached to the side of the tank or a central heating boiler. It’ll likely be found in an airing cupboard. You’ll have the option to choose from most taps and showers with this set-up, and because it is high pressure, you shouldn’t need to calculate your water pressure when buying new taps or a shower.
How do I calculate the exact water pressure in my home?
With low pressure water systems, it’s important to work out the water pressure to help you buy the correct shower or taps that can work effectively with the pressure you have. The water pressure is measured in bar, and the products designed for this pressure will be labelled accordingly.
To calculate the pressure, you can either ask a plumber to take a look, and they will use a pressure gauge tool, which you can also buy and use yourself. Or you can get a rough guide by measuring the drop between the tank and tap / shower, and we’ll show you how to do this below.
Start by measuring the height between the bottom of your open or vented water tank and the outlet of your tap or shower. You might find that this means measuring from your tap/shower to your ceiling, and then from the floor of your loft to the bottom of the tank. If there are floors in between, measure the height from floor to ceiling and add this all together. Don’t forget to allow for the depth of each floor too. Try to measure as accurately as possible, to the nearest metre.
Each metre of drop equates to 0.1 bar of pressure (see table below). Water systems which operate at 1.0 bar pressure (10m of drop) or greater are considered high pressure systems. Those with a pressure less than 1.0 bar are considered low pressure.
|1 metre||0.1 bar = Low pressure|
|2 metres||0.2 bar = Low pressure|
|3 metres||0.3 bar = Low pressure|
|4 metres||0.4 bar = Low pressure|
|5 metres||0.5 bar = Low pressure|
|6 metres||0.6 bar = Low pressure|
|7 metres||0.7 bar = Low pressure|
|8 metres||0.8 bar = Low pressure|
|9 metres||0.9 bar = Low pressure|
|10 metres +||1.0 bar = High pressure|
When you’re ready to choose a tap or shower, you’ll find the water pressure it is suitable for will be clearly labelled. Matching the right products to your pressure with ensure they work well in your home.
In some homes for example, a second floor shower might be 3 metres below the tank (0.3 bar = low pressure) but the ground floor or basement bathroom might have an 11 metre difference (1.1 bar = high pressure).
You can also make changes to your plumbing to increase your water pressure, for example by ensuring your stop valve is open (but not fully) or by installing the right pump, and we’ll explain this more, later in this article.
What taps are right for my water pressure?
If you have low water pressure, look for kitchen and bathroom taps which are labelled as suitable for high and low water pressure systems. Check that the minimum water pressure is the same as, or lower than your water pressure.
If you have high water pressure, you can choose from taps which are labelled as suitable for high and low water pressure systems, or high pressure only.
Which shower is right for my water pressure?
A low pressure system offers a good choice of showers. Mixer showers (with or without a pump), digital showers (with a pump), electric and power showers will all be suitable as long as the pressure requirement is achieved.
If you have high pressure (achieved with or without a pump), you will get a better flow rate and can consider big rain heads, body jets and the ability to have two or more taps or showers on at the same time.
A high pressure system will work well with a mixer, electric or digital shower. There is no need to install a pump as the water pressure should already be strong.
Pump it up
Adding a pump will help to boost low water pressure systems to give a better performance, but make sure you choose the right pump.
Positive pumps are designed to be fed by gravity. They require a distance of at least a metre between the bottom of the cold water tank and the pump to work.
Universal pumps (also known as negative pumps) do not require a gravity flow of water to function. They are suitable if the showerhead is either level with or above the cold-water tank, for example in a loft conversion.
You can also choose from a twin impeller pump or a single impeller pump. A twin impeller pump is designed for installation into both hot and cold-water supplies, boosting them equally. Single impeller on the other hand can only be installed into a single water supply – either hot or cold.
|1.0 bar shower pump||2.0 bar shower pump||3.0 bar shower pump|
|Boost a single outlet, for example a shower or tap.||For boosting increased demand ie large shower heads. For multiple outlets.||For multiple outlets. Entire house applications. For large shower heads.|
When selecting a pump, consider where it is being located. Pumps will work more efficiently when pushing water rather than pulling water. If possible, your pump should be installed on the floor next to the hot water cylinder and don’t forget accessibility to the pump for future repairs.