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40th Anniversary of the Hydraulic Valve

Now celebrating its 40th year, the hydraulic valve from Cistermiser has been designed to reduce water consumption in commercial washrooms. David Meacock, Technical Director, explains why the automatic flush control valve continues to stand the test of time.

40th Anniversary of the Hydraulic Valve

The heatwave of 1976 saw the hottest summer average temperature in the UK since records began, with highs of more than 32.5°C throughout the country for 15 consecutive days. The drought came at the end of what had already been an unusually dry year and some areas saw no rainfall for 45 days straight, leading to serious water shortage issues nationwide. Naturally, people began to think about ways they could save water. Alan North, who ran a plastic-injection moulding business, observed how cisterns flushed and realised there was an obvious way to reduce water consumption on a mass scale. From this, the hydraulic valve was born.

Although the country’s waning water stock was eventually replenished, Alan North’s invention endured, proving itself invaluable in saving water on a national scale. Alan designed and manufactured the valve himself, and its immediate popularity caused him to cease his trade moulding work and instead focus entirely on producing the valve. This shift was marked by his decision to change the name of his company to Cistermiser, a name that has now become synonymous with the hydraulic valve.

40 years on, the hydraulic valve employs exactly the same mechanical principle as in 1977. Now manufactured in Woodley, Reading, it is a simple, patented mechanism that prevents water wastage by ensuring that an auto-flush cistern is only filled, and can only flush, when the washroom is in use. 

Its sustained popularity can be largely attributed to the valve’s hydraulic mechanism, which means that no electrical supply or batteries are required. The mechanical basis means that it provides fit-and-forget quality, reliability and maximum convenience for installers and commissioners alike.

How it works
The hydraulic valve is installed on the supply pipe to the urinal cistern. It remains closed unless activated by the drop in pressure that occurs when a tap or WC is in use. When this happens, the valve will open and water will pass to the urinal cistern until the pressures on both sides of the internal diaphragm are equalised. When the cistern is full, the auto-siphon will flush.

The installer or user can adjust the time the valve will remain open for, and, consequently, how long the cistern takes to fill, and how much water will be used. When the washroom is not in use, the water supply pressure remains constant and the valve remains closed to prevent water passing into the cistern. Therefore, the cistern can only flush during periods when the washroom is in use, eliminating unnecessary water consumption and cost.

Cistermiser offers three different models, each suited to a different range of water supply pressures:

  Standard Valve, designed to accommodate mains water or tank-fed systems above 5m head.

  Low Pressure Valve, designed for tank-fed systems with 3m to 5m head.

• High Sensitivity Low Pressure Valve, a more acute version of the Low Pressure Valve, which can accommodate tank-fed systems with a 0.5m to 3m head.

For ease of identification, the valves come in different coloured packaging – purple for the Standard Valve, green for the Low Pressure, and orange for the High Sensitivity Valve.

In buildings where the washrooms are vacant for long periods of time, a hygiene cycle attachment is available to ensure a regular flush every 12 hours to prevent washroom odours. The bypass screw should be set to permit a slow drip into the cistern to initiate a flush approximately every 12 hours.

Test of time
Since its conception some half a million units have been installed in public buildings throughout the UK, including pubs, clubs, restaurants and leisure centres. A testament to its reliability is that it is now recommended that a hydraulic valve be installed in commercial washrooms under the Water Regulations.

The Water Supply (Water Fittings) Regulations 1999 states that: ‘Except in the case of a urinal which is flushed manually, or which is flushed automatically by electronic means after use, every pipe which supplies water to a flushing cistern or trough used for flushing a urinal shall be fitted with an isolating valve or another equally effective automatic device for regulating periods during which the cistern may fill’.

It also holds a position on DEFRA’s ECA Water Technology List, meaning that purchase and installation tax are deductible, making it a highly cost effective purchase for installers.

So while the Cistermiser range of washroom products becomes ever more sophisticated with infrared and other high technology solutions, there will continue to be a place for this pioneering and simple, yet highly effective, invention.

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