● A society of 171 flats.
● Located in Doddanekundi.
● Our borewell yield has been depleting.
● Lion’s share of maintenance gets spent on water bills.
● In 2016 we figured out - we have to do something about it.
The first effort to save water
● Door to door campaigns
● Drawing competition for kids
● Going green sessions
● Threats about implementing water rationing
Campaigns failed. But we learnt...
● Social ethics is not easy to build.
● People don’t really know what they are consuming.
● Accountability is the key.
● Campaign yields are too tiny.
● Rationing becomes counterproductive.
Three point solution
● Accountability - Flow meters & billing flats based on
● Reusability - Implement STP water plumbing to flush tanks on
● Generation - Increase the water source by tapping into
Flow meter - Challenges
● Multiple inlets to the flats.
● Entire apartment plumbing has to be fixed.
● Electronic solutions looked higher on OpEx.
● Multiple flow meters would make it harder to sustain.
Flow meter - Implementation
● Every flat replumbed to have a single inlet from the overhead
● Decided to go for cheap analog meters that also has long life.
● Connected water meters on terrace cleanly.
● Replaced existing GI pipes with good quality CPVC pipes.
Flow meter - Expense
● 25 mm Dashmesh B class flow meter
● Astral SDR 11 CPVC pipes connecting all inlets to flow meter.
● Astral plumbing fittings for all the connections.
● Total cost of 24,06,850₹ for the entire project.
● Per flat capital expense of 14075₹
Flow meter - Billing
● Benefit the conservative users and penalize heavy consumers.
● Incentivize by maintenance discount on saving water.
● Divide borewell yield share to flats per square feet basis.
● We also charge maintenance per square feet basis.
● Calculation example...
Flow meter - Billing example
● Let’s say there are two flats in the society.
● Flat 1 consumed 13000 litres of water and Flat 2 consumed 2500 litres of water.
● Flat 1 is 2000 sq ft and Flat 2 is 1800 sq ft. Totally society has 3800 sq ft.
● Borewell yield for the month was 8000 litres.
○ Flat 1 gets a share of (8000 / 3800) * 2000 = 4210 Litres.
○ Flat 2 gets a share of (8000 / 3800) * 1800 = 3790 Litres..
● Outside water spending was 2000₹
○ External per litre procurement cost is 2000 / (13000+2500 - 8000) = 0.266₹ per
● Flat 1 will pay a bill for the litres they consumed above their borewell share,
○ Bill will be (13000 - 4210) * 0.266 = 2343₹
● Flat 2 will get a discount for their savings in maintenance,
○ Bill will be (2500 - 3790) * 0.266 = -343₹
STP water reuse - Implementation
● Sewage Treatment Plant improved to have additional final
● Implemented dual pipeline to the flats and connected flush
tanks to STP line.
● Minimal drilling and cutting work inside the bathrooms.
● Two large overhead tanks supplies water to eight smaller
tanks on four blocks.
● No water meter for flush tank pipe line.
STP water reuse - Expense
● Astral SDR 13.5 CPVC
● Astral Plumbing fittings
● Sintex Plastic water tanks
● Metal and concrete tank mounts
● STP additional tank replenishment
● Total cost of 22,81,927₹
● Per flat capital expense of 13344₹
● Implemented rainwater collection system for all our terraces.
● Water from rainwater collection goes to two large filters.
● Filtered water is sent to water sumps and borewell recharge
● Filters and terrace cleaned periodically to keep water clean.