Ball valves are vital parts of the plumbing system in the home, since they control the amount of water in your cold water storage and WC cisterns. They must operate efficiently, otherwise the cisterns will overflow – or not fill up correctly.
The purpose of the bail or float, valve is to maintain water at a constant level in cold water storage and WC flushing cisterns. All ball valves have a metal or plastic arm terminating in a float (not necessarily a ball) that rises or falls with the level of the water in the cistern. As the water level falls the movement of the float aim opens the valve to allow water to flow through it: as the level rises the arm closes the valve. The old types of ball valve the Croydon and the Portsmouth control the flow of water by a washered metal plug. The main disadvantage of these is that failure of the washer or dirt or corrosion on the parts can cause leaks. Modern ball valves, which have a rubber diaphragm instead of a washered plug, are designed to overcome these problems.
Croydon and Portsmouth valves
On both these valves a washered metal plug is forced tightly against the valve seating to prevent a flow of water when the cistern is full. The plug of a Croydon moves vertically within the valve body. When the valve is open, water splashes into the cistern via two channels built into either side of the body of the valve. Croydon valves are always noisy in action and, for this reason, are now rarely, if ever, installed in homes.
The Portsmouth valve is the one now most likely to be found in installations, particularly new ones. Its plug moves horizontally within the valve body and the end of the float arm is bent over to fit within a slot built into the plug. The noise of these valves used to be reduced by fitting a silencer tube into the valve outlet. This is a plastic or metal tube that delivers incoming water below the level of the water already in the cistern; it eliminates splashing and reduces the ripple formation that is a common cause of noise and vibration in ball valves. Unfortunately water authorities no longer permit the use of these silencer tubes, since in the event of water pressure failure they could cause water from storage and flushing cisterns to siphon back into the main.
Dealing with leaks
A steady drip from the cistern’s warning pipe indicates a worn washer a common fault on the Croydon and Portsmouth valves. It may be possible to cure the leak, at least temporarily, without changing the washer simply by lowering the level of the water in the cistern. There is no need to cut off the water supply to do this: remove the cover from the cistern, unscrew and remove the float from the end of the float arm. Take the arm firmly in both hands and bend the float end downwards, then reassemble. This will keep the water below the normal level, which is about 25mm below the warning pipe in a cold water storage cistern and l3mm below the warning pipe in a flushing cistern. (If you need to raise the water level in a cistern, bend up the float end of the arm.)
Changing the washer
If lowering the level of the water does not cure the leak, you will need to change the ball valve washer. First cut off the water supply at the nearest stopcock. Some Portsmouth valves have a screw-on cap at the end of the valve body: this must be removed. Straighten and pul1 out the split pin on which the float arm pivots and remove the float arm; insert the blade of a screwdriver in the slot in the base of the valve body from which the float arm has been removed and push out the plug. The plug has two parts: a body and a cap retaining the washer, but it may be difficult to see the division between these parts in a plug that has been in use for some time. To replace the washer you will need to remove the retaining plug: insert the blade of a screwdriver through the slot in the body and turn the cap with a pair of pliers. This can be very difficult, so don’t risk damaging the plug. If the cap will not unscrew easily, pick out the old washer with the point of a penknife and force a new washer under the flange of the cap, making sure the washer lies flat on its seating.
It is important to remove any dirt on the metal parts. Before reassembling the plug, clean it with fine abrasive paper and smear with petroleum jelly.
When to replace the valve
Continued leaking after renewal of the washer may indicate the valve seating the plug has been scored by grit from the main or water outlet r valve seating water outlet a low pressure valve has been fitted where a high pressure one is required. In either case, a new valve will be needed. Ball valves are classified as high pressure (HP) or low pressure (LP) depending on the diameter of the valve seating and are usually stamped accordingly on the valve body. High pressure valves are usually installed where the water supply is direct from the main and low pressure valves where the water supply is from another storage cistern, as is usually the case with WC flushing cisterns. Using the wrong kind of valve will result in either constant leaks or a long delay in the refilling of the cistern. Where a WC flushing cistern is supplied from a cold water storage cistern only a metre above the level of the WC suite, it may be necessary to fit a full-way valve – which has a wider orifice – to ensure the cistern refills rapidly after it has been flushed.
In some areas water pressure may fluctuate considerably throughout a 24h period. In such cases, the provision of an equilibrium valve is recommended. This valve has a wide nozzle orifice but is closed by a special plug with a channel bored through its centre: this allows water to pass through to a sealed chamber behind the valve. The plug is therefore in a state of equilibrium: water pressure is equal on each side of the plug and the valve opens only at the prompting of the float arm – not partly as a result of the pressure of water in the rising main trying to force the valve open. An equilibrium valve is also useful in preventing water hammer – shock waves produced when the conflict between water pressure in the rising main and the buoyancy of the float result in the valve bouncing on its seating.