What are the standard capacities of automatic flushing cisterns?

The standard capacities are 5, 10, and 15 litres.

What is the minimum discharge performance for a 5-litre cistern?

It must completely discharge 5 litres in not more than 15 seconds.

Does this standard apply to modern plastic urinal cisterns?

No, plastic flushing cisterns are specifically excluded and covered under IS 7231.

IS 2326

: 1987

Automatic Flushing Cisterns for Urinals (Other than Plastic Cisterns)

CurrentSpecializedSpecificationBIMMEP · Sanitary Appliances and Water Fittings

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This standard specifies the requirements for materials, manufacture, nominal capacities, dimensions, and testing of automatic flushing cisterns used for urinals. It explicitly excludes cisterns made of plastic materials.

Automatic Flushing Cisterns for Urinals (Other than Plastic Cisterns)

Quick Reference Values

standard capacities5, 10, and 15 Litres

discharge time 5LMax 15 seconds

discharge time 10LMax 25 seconds

discharge time 15LMax 35 seconds

minimum thickness cast iron5.0 mm

minimum thickness pressed steel1.60 mm

flush pipe internal diameter 5L15 mm minimum

Practical Notes

For plastic automatic flushing cisterns, refer to IS 7231 instead.

Ensure the internal diameter of the flush pipe strictly matches the cistern capacity to achieve the specified discharge velocity and time.

The syphon mechanism must be calibrated properly as hard water scaling can quickly alter the automatic flush intervals.