Page 326 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Float-operated valves to BS 1212

Float-operated valves are used to control the flow of water into cold water
storage and feed cisterns, feed and expansion cisterns, and WC cisterns. They
are designed to close when the water reaches a pre-set level. They are made to
BS 1212 and it is important that plumbers recognise the different types. There
are four basic float-operated valve types:
1 BS 1212 Part 1: Portsmouth pattern and Croydon pattern
2 BS 1212 Part 2: Diaphragm type
3 BS 1212 Part 3: Diaphragm type (plastic)
4 BS 1212 Part 4: Torbeck equilibrium type (WC cisterns only).
Float-operated valves can either be high pressure or low pressure depending
on the type of orifice fitted. The orifice is the part of the valve that the water
passes through. A high-pressure orifice is white in colour and has a small hole
for the water to flow through, whereas the low-pressure orifice is coloured red
with a larger hole. The orifice is universal for Parts 1, 2 and 3 float-operated
valves.

BS 1212 Part 1 Portsmouth pattern float-operated valve
The Portsmouth-type float-operated valve discharges water from the bottom
of the valve, which makes it susceptible to back siphonage should the valve
become submerged in water. It should not be fitted on new installations without
some form of backflow protection device, although existing Portsmouth-type
valves can be repaired and maintained.
Portsmouth float-operated valves have moving parts that will come into
contact with water, and this makes them vulnerable to failure and noise.

Union Orifice Piston

End cap

Lever arm

Washer

p Figure 5.94 A BS 1212 Part 1 Portsmouth-type float-operated valve

BS 1212 Part 1 Croydon pattern float-operated valve
The Croydon-type float-operated valve is less common than the Portsmouth
type. Like the Portsmouth, it discharges water from the bottom of the valve,
but it is easily recognisable by its vertical piston and by the fact it delivers
water into the cistern in two streams. This type of float-operated valve is very
noisy and no longer manufactured, but it may still be used in some older WC
cisterns.

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