Water in a Bengaluru flat

A flat’s water rarely comes from one place. Most of it is Cauvery water piped in by the Bengaluru Water Supply and Sewerage Board (BWSSB), but almost every apartment also leans on a second or third source: a borewell it owns, a tanker it calls in, or its own sewage treatment plant (STP) recycling wastewater back into flush tanks and gardens. Which of these a building actually uses, and how legally, differs enormously between projects, and a brochure rarely says.

Each source sits under a different law, with a different regulator and its own paperwork. A BWSSB connection is tied to the building’s occupancy certificate. A borewell needs a permit or a no-objection certificate from the Karnataka Ground Water Authority (KGWA), with a real but limited exemption for ordinary domestic use. A tanker selling groundwater in bulk needs its own NOC. An STP above a certain size needs consent from the Karnataka State Pollution Control Board (KSPCB), and has to reuse what it treats rather than let it run to waste. And any new building of real size is expected to harvest its own rain.

This guide takes each source in turn: what triggers the rule, who enforces it, and what to ask a builder to show you before you pay anything.

Four sources, one flat

BWSSB: the piped supply

BWSSB draws from the Cauvery under its own staged water-supply scheme and delivers it through its mains to every connection it grants. For an apartment, that connection is not automatic. Under the Greater Bengaluru Governance Act, 2024, a City Corporation cannot let anyone occupy a new building, in whole or in part, until it has issued an occupancy certificate (OC) for it, or for the part being occupied – and the Act is explicit that BWSSB and BESCOM may not give the building a permanent water or power connection until that OC exists (s.246(5)). A part-finished project can still take a partial OC, and a matching partial connection, for the block that is ready (s.241(5)). What neither BWSSB nor BESCOM can do is connect a building, or any part of it, on a promise that the OC is coming.

That makes the OC the single most useful thing to ask for at handover – not the demand note. A builder who has paid BWSSB’s charges and been issued a demand note has started the process; only the OC finishes it. Our documents guide covers how to read an OC and what else should accompany it.

What a connection actually costs

Getting the connection itself involves up to three separate charges under the BWSSB Act, and a buyer should expect all three to have been paid before an OC and a working connection exist:

• A connection charge for the metered service itself.
• Pro-rata charges: the proportionate cost of extending or upgrading the water and sewerage network to reach the site, billed to the owner, occupier or developer at the Board’s own assessment, revised from time to time (s.2(17a)). Leaving them unpaid attracts a further penalty of up to 25% on top (s.109A); taking an unauthorised connection without paying them at all can be charged up to 50% on top of the pro-rata amount itself (s.109A, as substituted in 2013).
• A beneficiary capital contribution, where a project sits in an area BWSSB is extending its network under a government-directed scheme (s.89A). The power to collect it was itself challenged in the Karnataka High Court as unsupported by law; the legislature responded by validating past collections retrospectively from 1 January 2003 rather than let the challenge stand – a reminder that this is a charge worth seeing a receipt for, not simply a demand-note figure to accept on trust.

None of these is a flat, published statewide rate. BWSSB assesses pro-rata and capital-contribution charges project by project, against what its network actually needs to reach the site. The document to ask for is the paid demand note and connection sanction, not an estimate.

Borewells and the law

Karnataka regulates groundwater under one law, the Karnataka Ground Water (Regulation and Control of Development and Management) Act, 2011, run by KGWA. Since it was amended in September 2025, the core rule applies everywhere in the state, not only in areas the government has specifically notified: no one may drill or dig a well, or extract groundwater for any purpose, without a permit or a no-objection certificate from the Authority (s.11(1)).

There is a real exemption for ordinary living, and it matters for how you read a project’s paperwork. Individual domestic users, and residential apartments or group-housing societies, need no permit or NOC at all if their borewell draws no more than 20 cubic metres – 20,000 litres – a day for drinking and domestic use (s.11(1-A)(vi)). Above that draw, a project’s borewell use should be backed by an actual permit or NOC, not just a claim of exemption.

Where a borewell was already in use before an area was declared “notified”, its owner had 120 days from that declaration to register the existing use (s.12), and the firm that drilled it has to be separately registered with KGWA as a drilling agency (s.13). Drilling without a permit is a punishable offence: a fine of up to ₹5,000 or up to six months’ imprisonment, with the well and equipment liable to be seized (s.32(2)).

Parts of the wider Bengaluru area have been formally declared over-exploited. Karnataka Gazette notifications from 2017 and 2020 place Anekal taluk (Bengaluru Urban district) and Devanahalli, Doddaballapur, Hoskote and Nelamangala taluks (Bengaluru Rural district) on that list, building on a March 2013 Central Ground Water Board assessment; KGWA applied there from 1 January 2018. A borewell anywhere in these areas needs the full registration route, on top of the state-wide permit rule that now covers every other part of Karnataka too.

Tankers: the backstop

A tanker is water brought by road, and Karnataka regulates it at the point the tanker gets its water rather than at the point it delivers it. Any private tanker that draws groundwater to sell in bulk – which is what most tanker operators do – needs its own no-objection certificate for that abstraction from the ground water authority (s.11(1-B)). A tanker without one is drawing water the same way an unregistered borewell would.

BWSSB itself runs an alternative: a tanker-booking service on its own site, delivering piped Cauvery water rather than groundwater, as a competitor to private operators. For a building leaning on tankers as more than an occasional top-up, two questions matter: where does the water come from, and does whoever sells it to the building hold the NOC the law requires for that source. Neither is answered by the delivery receipt alone.

Sewage plants and reuse

Above a certain size, a Bengaluru apartment is required to treat its own sewage rather than send it straight to the public system. The trigger, set by a 2016 state government notification and applied by KSPCB, is either 20 dwelling units or more, or a total built-up area of 2,000 sq m or more including basements. The two conditions are independent, and the area condition can bind earlier than the unit count suggests: at an illustrative 1,600 sq ft a flat, a project needs only about 14 flats to cross 2,000 sq m – well under the 20-unit trigger on its own.

An STP needs its own consent from KSPCB in two stages, tracing back to the Water (Prevention and Control of Pollution) Act, 1974: Consent to Establish before construction, and Consent to Operate before it runs (ss.24–25). Both should exist as documents, not just as a tank shown on the site plan.

The point of the STP is not only to stop sewage reaching a drain untreated. KSPCB’s own guidance requires the treated water to be put back to use on site. Toilet flushing must run on the treated supply through a separate, dual plumbing system; gardens and landscaping are costed at 5 litres per square metre of landscape area; and treated water can go into some construction work, short of anything touching load-bearing steel. A flat’s own dual-flush plumbing, in projects that carry an STP, is close to compulsory rather than a green extra the builder chose to add.

Rainwater harvesting

Rainwater harvesting is the one obligation that falls on every sizeable new building, not just large ones. Under the BWSSB Act, anyone building on a site of 1,200 sq ft or more must provide a rainwater harvesting structure, to store water for use or to recharge groundwater; for a building that already exists, the threshold is 2,400 sq ft (s.72A). The Greater Bengaluru Governance Act repeats the same duty for every khatadar sanctioning a new building plan, pointing straight back to the BWSSB Act and BWSSB’s own regulations for the detail (s.225).

The Act leaves the manner and conditions to BWSSB’s regulations and guidelines rather than fixing a structure size in the law itself, and a failure to comply falls under the Act’s general penalty: up to six months’ imprisonment or a fine of up to ₹5,000, with a further ₹500 for every day a failure continues after conviction (s.109). Where a site sits inside a KGWA-notified area, a second, parallel duty applies from the Ground Water Act itself: any premises of 100 sq m or more must have a rainwater harvesting structure before it can get a permanent water or power connection at all (s.22).

Put the size thresholds that drive a building’s water obligations on one scale, and the gap between them is the point:

Documents to ask for

What each water-related document actually proves, and where you can check it yourself before you rely on it:

Before you buy

• Ask for the source mix: what share of daily supply is BWSSB, what share borewell, what share tanker, and how that changes in summer.
• Ask for the OC, not the demand note, before treating the water connection as settled.
• Check the borewell’s status: a permit, an NOC, or the actual daily draw behind any claimed exemption.
• Ask whether the project needs an STP, and if so, for its Consent to Establish and Consent to Operate, not just its existence.
• Check the rainwater harvesting structure exists and works, not only that it is marked on the sanctioned plan.
• If tankers are a real part of supply, ask who the suppliers are and whether they hold their own groundwater NOC.