Diaphragm and Equilibrium Ball Valves
Diaphragm and Equilibrium Ball Valves
Diaphragm and Equilibrium Ball ValvesSo the next time one of yours goes wrong, be prepared to put it right yourself.
Ball-valves are really just self-regulating taps designed to maintain a given volume of water in a cistern. While there are a number of different patterns they all have afloat-not necessarily a ball these days - at one end of a rigid arm which opens or closes a valve as the water level in the cistern falls or rises.
There are basically two types of ball-valve: the traditional type, generally made of brass, in which the water flow is controlled by a washered plug or piston; and the type that has been developed more recently in which the flow is controlled by a large rubber diaphragm housed within a plastic body. Here we will discuss Diaphragm ball-valves and Equilibrium ball-valves.
Diaphragm ball-valves
Diaphragm ball-valves, which are also referred to as BRS or Garston ball-valves, were specially developed to overcome the noisiness and inherent faults of the Croydon and Portsmouth valves. Since the moving parts of a diaphragm valve are protected from incoming water by the diaphragm there is no risk of them seizing as a result of scale deposits and the problem of noisy water delivery is often overcome nowadays by an overhead sprinkler outlet which sprays rather than squirts the water into the cistern. Should you need to adjust the water level in a cistern fitted with a diaphragm valve, then invariably you can by means other than bending the float arm. The only problems you are likely to encounter with diaphragm valves are jamming of the diaphragm against the valve nozzle, and obstruction of the space between the nozzle and diaphragm with debris from the main. You remedy these problems by unscrewing the knurled retaining cap and either freeing the diaphragm with a pointed tool or removing the debris.
Equilibrium ball-valves
You can buy Portsmouth and diaphragm equilibrium valves. These are both designed to allow a small quantity of water to pass through or round the washered piston (or diaphragm) into a watertight chamber beyond. Acting as it does on the rear of the piston, and being at the same pressure as the mains, the water in the chamber ensures that the piston is held in equilibrium. What this means in practice is that the valve is operated solely by the movement of the float arm, rather than by a combination of the movement of the float arm and the pressure of the incoming water as is the case in an ordinary high-pressure valve. In addition to refilling your cistern promptly regardless of any fluctuations in mains pressure, equilibrium valves also eliminate the 'bounce as the valve closes - a common cause of water hammer. A diaphragm equilibrium valve will give you a particularly rapid and silent refill.
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