Portsmouth-type float valve.

The most common type of ball or float valve in the UK is known as the Portsmouth piston. Made of brass and virtually indestructible, the valve is opened and closed by means of a cylindrical plug that moves backwards and forwards within a horizontal chamber. When the ball float is in the ‘up’ position, the other end of the float arm pushes the plug along its chamber, with the result that a rubber disc at the end of the plug is pressed hard against the water inlet nozzle cutting off the water. A Hampstead Plumber fits this valve. When the ball float is in the ‘down’ position, the float arm pulls the plug back along its chamber, with the result that the rubber disc located at the end of the plug eases away from the water inlet nozzle, allowing water into the cistern. A Croydon valve operates along much the same lines, the difference that the plug moves vertically instead of horizontally. The servicing of both types of valves involves cleaning the piston and/or replacing the rubber disc. While the Portsmouth valve and the much older Croydon are both available, modern diaphragm valves are in many ways a more efficient option.

Diaphragm-type float valve.

This valve is a ball or float valve and made of plastic and rubber. In action it is much the same as the traditional brass valve, with the float being lifted up and down by the level of the water. But when it comes to the business end of the arm, the working action is such that when the water rises, a plastic piston pushes against the rubber window or diaphragm, with the effect that the rubber disc on the other side of the diaphragm pushes against the water inlet nozzle to cut off the water. Hampstead Plumbers know how these valves work. Of course, when the water level drops, the float falls, with the effect that the other end of the arm ceases to press against the diaphragm and the water flows out of the nozzle.
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