Types of Float Valves

The float valve has been in plumbing service for a long time in one form or another. There are a few examples, and below is a description of a couple the float type valve:

Portsmouth.

A valve that is quite commonly found in british plumbing. It is also known as the Portsmouth Piston. Manufactured in brass and very resilient, this valve uses a cylindrical shaped plug, moving in a horizontal chamber to open and close. When the fitted ball float is up, the opposite end of the float arm moves the plug along the chamber, and a rubber disc at the end of the plug is pressed hard against the water inlet nozzle cutting off the water. An Ilford Plumber can fit this valve. If the ball is down, the float arm pulls the plug back through the chamber, and the rubber disc at the end of the plug moves away from the inlet nozzle, allowing water into the cistern.

Diaphragm.

Manufactured from rubber and plastic material, a diaphragm valve works almost the same as its older brass counterpart, as the float lifts up and down by the level of water. But slightly different, is, as the water starts to rise it acts on a plastic type piston causing it to fall on a rubber diaphragm so that the rubber disc on the other side of the diaphragm presses against the water inlet nozzle, cutting off the water. Similarly, as the water level lowers, the float follows, and the pressure is reduced on the diaphragm so the water flows out of the nozzle. Ilford Plumbers work on valves and know how they work.

Note:
A croydon valve operates similarly, the only difference is that the plug moves vertically not horizontally. These valves are usually maintained by cleaning the piston and/or replacement of the rubber disc.