Technology

Cistern displacement or dual flush

Cistern displacement or dual flush
© hansgeel, image #108262362, 2017, source: Fotolia.com
Sector:
All sectors
Investment cost:
Low cost
Payback time:
0.15 - 0.8 Year(s)
Cost savings:
30% / 23 - 137€ / Annual savings in water consumption are assumed to approximate €23 per toilet, and €137 per toilet if located in a public building.
Investment cost:
20€ / Investment cost depends on the scale of the project.
Payback time:
Approximately 10 months. Can be 2 months if toilet use is high (e.g. for public buildings)

Cistern displacement or dual flush? Your choice

Cistern displacement and dual flush are increasingly popular water-saving techniques. Authorities in many water-stressed places, for instance, are pushing this low-flush approach to safeguard a precious resource.

Dual-flush mechanisms are usually incorporated in new low-flush toilets, but may also be retrofitted to existing cisterns. These mechanisms have two buttons; one launches a full flush (e.g. 6 L) for solid materials; the other a half-flush (e.g. 3 L) for urine or liquids.

Average water use is calculated on the basis of one-third of flushes being full and two-thirds half. Dual flushing cuts water use in toilets by around 33 % compared to your average consumption.

Cistern displacement uses bags of water, granules or pebbles inserted into the water housing (cistern) to reduce volume. It can also be achieved by adjusting the float-arm to reduce the fill level of the cistern.

This technique can save between 0.5 and 2 litres of water per flush. It is a relatively simple retrofit, and has proven to be very efficient where the toilet use is high (e.g. in public buildings).

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