Before selecting a tap/shower, you should establish the level of water pressure you have in the bathroom. This is because many taps/showers require high pressure to function correctly.
Unless the cold water is supplied to your bathroom direct from the rising main at mains pressure (approx. 2.0 bar), which is unlikely, both the hot and cold water pressure must be above 1.0 bar if they are to supply a high pressure tap or shower. If below this, you will only be able to install a low pressure tap/shower to function effectively.
What is bar?
Water pressure is measured in three common units: bar, psi and Head (m).
1 metre (3ft 3in) Head = 0.1 bar = 1.45 psi
You can calculate pressure by measuring the vertical distance in metres between the bottom of the cold water storage (header) tank and the water outlet (tap or shower). This figure is the water pressure in Head (m). Divide this by 10 to calculate bar.
The hot water from your heating system (boiler) will be at high pressure if you have one of the following; An unvented (pressurised) system, wherein mains cold water directly supplies all cold taps and also travels direct to the hot water cylinder, keeping it at high pressure. A combination boiler, which is fed by the mains and heats hot water as you use it. A gravity fed system with a pump added to increase water pressure to more than 1.0 bar.
If you have an unpumped gravity-fed system, where the cold water tank is less than 10 metres above the tap, you should use a low pressure bathroom tap. You can of course add a pump to your system to boost the pressure, which will increase your choice of tap considerably.
Generally speaking, single lever mixer taps require high water pressure, while pillar taps and taps with two handles to control water flow (often referred to as fillers) can function with low pressure. Thermostatic showers and bath shower mixers generally require high pressure systems - unless otherwise stated.
Here is a quick and simple guide to calculating the output required to heat your bathroom.
1 - Multiply your room length x width x height (all in feet) = room volume in cubic feet.
2 - Multiply the room volume by 5
This figure gives a rough guide to the required heat output in BTUs.
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