Water Pressures - Understanding How Your Water Is Supplied
	Many manufacturers of water fittings (eg taps, showers) give a minimum water pressure rating at which the equipment should operate.  The notes below provide guidance on what this means in practice.
	What Does 'Any Pressure' Mean?
	What Does 'Medium Pressure' Mean?
	What Does 'High Pressure' Mean?
	What Does 'Mains Pressure' Mean?
	What Are Combination Boilers?
	What Does 'Gravity/Tank Fed' Mean?
	What Are Pumped Systems?
	What Are Unvented Pressurised Systems?
	What Does 'Bar' Mean?
	Any Pressure
	Suitable for all water supply types... Gravity / Tank Fed Systems Combination Boilers Pumped Systems Unvented / Pressurised Systems
	Medium Pressure
	Although these fittings are suitable for low pressure, a minimum of 0.5 bar is recommended for best performance... Gravity / Tank Fed Systems (whereby the tank is located 5 metres above the tap of the shower outlet) Combination Boilers Pumped Systems Unvented / Pressurised Systems
	High Pressure
	These fittings require a minimum operating pressure of 1 bar for best performance... Combination Boilers Pumped Systems Unvented / Pressurised Systems
	Combination Boiler
	A mains fed system that instantaneously heats cold water when a tap or shower is turned on. The major difference between a combination and any other type of boiler is that it eliminates the need to store hot water - so no hot water cylinder in the airing cupboard or tanks in the loft. This type of boiler delivers water to the taps or shower at mains pressure. Identify this system: Usually consists of a white-cased boiler without any tanks or hot water storage cylinders. The boiler would normally have a pressure gauge visible alongside other controls on the bottom front panel.
	Gravity/Tank Fed
	Until 1998 this was the most commonly installed hot water system in the UK and is easily identified by the use of a cold water storage tank (usually in the loft) and a hot water storage cylinder. The water pressure generated by this system is directly related to the height of the cold water storage tank. To calculate the available pressure simply measure the distance, in metres, from the bottom of the cold water tank to the outlet of the tap or shower and multiply by 0.1. This will calculate the pressure in bar... 2 metres x 0.1 = 0.2 bar 5 metres x 0.1 =0.5 bar Identify this system: The storage vessel (cylinder) can be situated anywhere in your house. You will typically find it in the bathroom, adjoining room or loft. Cylinders are usually insulated to prevent heat loss; the insulation will usually be red, green, or blue.
	Pumped Systems
	Gravity systems with the addition of an inline booster pump to increase pressure to one or more outlets. Pumps are available with differing pressure capabilities starting with a single outlet booster pump capable of providing an intense fast flowing shower, right through to a multiple outlet pump that will satisfy the hot water requirements of the whole house. Booster pumps are typically selected by the pressure in bar that they provide. Identify this system: A booster pump will normally be found alongside the hot water cylinder. This will operate when a hot tap or shower is turned on.
	Unvented Pressurised Systems
	A mains pressure cylinder heated by an electric element, conventional or combination boiler. Above the cylinder you will find an expansion vessel (round steel container) and a water pressure gauge. This type of system delivers water to the tap or shower at mains pressure. Identify this system: Unvented cylinders are normally larger than a standard cylinder and have more complex pipework and fittings that include an expansion vessel and a pressure gauge.
	Bar
	The measurement of water pressure. 0.1 Bar (1.45 psi) is equal to approx one metre of height between the bottom of the water tank and the outlet of the tap or shower.
	Mains Pressure
	The pressure of the water supply entering the house measured from the stop tap. Water companies are obliged to maintain a minimum flow of 9 litres per minute with the lowest pressure requirement being 1 bar.