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BS 1125:1987


The latest, up-to-date edition.

Specification for WC flushing cisterns (including dual flush cisterns and flush pipes)
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Hardcopy , PDF



Published date


Committees responsible
Section one. General
1 Scope
2 Definitions
3 Marking
Section two. Materials and design
4 General requirements
5 Requirements for particular materials
6 Soft solder
7 Hard solder
8 Flushing apparatus
9 Volume of discharge per flush
10 Rate of discharge
11 Water line
12 Spill-over level
13 Warning pipes
14 Float operated valves
15 Covers
Section three. Construction
16 Shell
17 Operating lever and pull
18 Flush pipe connection
19 Bottom connection cisterns
Section four. Flush pipes
20 General requirements
21 Special requirements for flush pipes for use with
    cisterns at high level
22 Special requirements for flush pipes for use with
    cisterns at low level
A Distortion and dead load tests
B Front thrust test
C Impact test
D Volume of discharge test
E Rate of discharge test for full flush
F Options: Information to be supplied by the purchaser
1 Flush pipes
2 Front thrust test apparatus
3 Test flush pipe for low level cistern

Cisterns with valveless siphons, nominally 9 litres, for high level, low level and close coupled positions, in both ceramic and plastics.

BS 1125 specifies requirements for WC flushing cisterns with valveless siphons, nominally 9 L (litres), for high level, low level and close coupled positions, together with the necessary flush pipes.

The cisterns specified are of the type which flushes 9 L only, (i.e. the single flush type), or of the type which flushes, as selected, either 4.5 L or 9 L, (i.e. the dual flush type).

Float operated valves and methods of fixing are not covered by BS 1125.

NOTE 1 Dual flush type cisterns are intended for use with washdown pans in domestic premises only.

NOTE 2 The titles of the publications referred to in this standard are listed on the inside back cover.

Supersedes 85/13284 DC and BS 1125(1973). (06/2005) Reviewed and confirmed by BSI, December 2012. (11/2012)
British Standards Institution

BS 1212-4:1991 Float operated valves Specification for compact type float operated valves for WC flushing cisterns (including floats)
BS 2456:1990 Specification for floats (plastics) for float operated valves for cold water services
BS 3402:1969 Specification for quality of vitreous china sanitary appliances
BS 2871-1:1971 Specification for copper and copper alloys. Tubes Copper tubes for water, gas and sanitation
BS 1212-1:1953 Specification for ballvalves (excluding floats) Piston type
BS 2782-5:Method 540B:1982 Methods of testing plastics. Optical and colour properties, weathering Methods of exposure to laboratory light sources, (xenon arc lamp, enclosed carbon arc lamp, open-flame carbon arc lamp, fluorescent tube lamps)
BS 3830:1973 Specification for vitreous enamelled steel building components
BS 2799:1974 Specification for power-driven tower cranes for building and engineering construction
BS 5503-1:1977 Vitreous china washdown WC pans with horizontal outlet Connecting dimensions
BS 1845:1984 Specification for filler metals for brazing
BS 1212-3:1979 Specification for float operated valves (excluding floats). Diaphragm type (plastics body) for cold water services
BS 5504-4:1990 Wall hung WC pan Specification for wall hung WC pans for use with 7.5 L maximum flush capacity cisterns
BS 1212-2:1970 Specification for ballvalves (excluding floats) Diaphragm type (brass body)
BS 4781-1:1973 Specification for self-adhesive plastics labels for permanent use General purpose labels
BS 2782-5:Methods 530A and 530B:1976 Methods of testing plastics. Optical and colour properties, weathering Determination of yellowness index. Determination of the colour of near-white or near-colourless materials

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