Plumbing Systems, Pressure & Taps
Will the tap be suitable for my plumbing system?
This aim of this post is to help you answer the above question. To answer this question however we need to take a look at the various types of plumbing systems typically installed in residential premises. These are:
- Gravity Fed Systems (a type of indirect system)
- Combi Boiler Systems (a type of direct system)
- Unvented Systems (a type of direct system)
When discussing these systems, we will not discuss the pros and cons, just their impact on the taps in the system.
1. Gravity Fed Water System
The gravity fed system is considered a low pressure system (below 1 bar pressure). Water comes in from the mains pipe and feeds the kitchen tap and a water storage tank usually found in the attic. In this type of system, only the cold water at the kitchen tap and the storage tank will be at mains pressure, as they are fed directly by the mains system. The rest of the taps & showers in the house will be gravity fed. The cold water storage tank feeds a hot water cylinder and the rest of the taps and fittings with cold water. In turn, the hot water from the cylinder is fed to the taps and showers as below:
To calculate the water pressure or “head” of the gravity feed in your house, you can assume that every metre of head will give you 0.1 bar pressure. This means that if there is a distance of 5 metres from your tap to the cold water storage tank then you have a water pressure of approximately 0.5 bar. This is usually less due to bends in the pipework and restrictions through fittings.
How does this impact my taps:
Kitchen Taps: The tap will usually have unbalanced pressure as the cold water will be at mains pressure and the hot water will be at whatever “head” of pressure the gravity feed gives. We usually recommend at least 0.5 bar hot and cold water to kitchen taps to give an adequate flow rate. This is especially important for taps with Pull Out/Multi Function Heads due to their restrictive routes. Mixer taps compensate for unbalanced pressure to some extent but balanced pressure is recommended for mixer taps for best performance.
Bathroom Taps: These taps will have balanced pressure as they will both be fed by gravity. Upstairs will have slightly less “head” as they are closer to the water storage tank than kitchen taps downstairs. For bathroom taps we also recommend 0.5 bar pressure but lower pressures will also be adequate in some cases as basin and bath taps are relatively straight forward.
Can I improve the pressure in a gravity fed system:
Yes, a pump can be installed to improve the pressure. These pumps increase the pressure from the hot and cold supply if you feel the current pressure is inadequate. This is a subjective thing and some home owners will accept a lower flow rate than others.
2. Combi Boiler Systems:
Combi boilers or combination boilers combine water heating and central heating in one boiler. These are usually found in apartments or smaller homes or homes with no loft spaces. If you have this system you will not have a cold water storage tank or a hot water storage tank, as water is heated directly from the mains water supply and distributed all around the house.
How does this impact my taps:
Both your kitchen and bathroom taps will be supplied at a balanced mains pressure. The pressure will depend on the area you live but will usually be at high pressure (above 1 bar).
3. Unvented Systems:
In an unvented system, there is also no cold water storage tank required. The hot water storage tank is fed at mains pressure by the incoming cold water mains supply and in turn distributes hot water around the house at mains pressure. The hot water storage tank is strengthened to cope with the higher pressure and is heated by immersions or the central heating boiler (indirectly).
How does this impact my taps:
As with the combi system both your hot and cold water taps will be fed with balanced hot and cold water supplies at mains pressure. This means that you will most likely have a high pressure system (above 1 bar).
Final notes:
Anything below 1 bar pressure is considered to be a low pressure system and anything above 1 bar pressure is considered to be a high pressure system. As above you can check to see if the pressure in your home will support the product you buy. All of our products at www.thetapshop.ie have a product table that tells you the pressure you need for each tap.
