The short answer: five persons per tenement, for every tenement. Regulation 12.5 sizes a residential building's water supply on a flat rate assumption rather than on unit sizes, which is worth knowing before assuming a large flat was provided for generously.
Key takeaways
- Water supply, drainage, sanitation and gas systems follow Part 9 of the National Building Code, as amended.
- For a residential building, the total water requirement is calculated at five persons per tenement.
- For other buildings it is based on the occupant load and the areas of floors in the code's table.
- Every overhead water storage tank must be mosquito proof with a properly fitting hinged cover.
- Every tank more than 1.5 m in height must have a permanently fixed iron ladder.
- Every building or group of buildings must connect to a drainage system, or have a septic tank.
The basis
Chapter 12, Regulation 12.5, UDCPR as updated 30 January 2025* does two things. It routes the technical design outwards, and it fixes the population assumption inwards.
The planning, design, construction and installation of water supply, drainage and sanitation and gas supply systems shall be in accordance with Part 9 of the National Building Code of India, Section 1 for Water Supply, Drainage and Sanitation and Section 2 for Gas Supply, as amended from time to time.
The total requirement of water supply is then calculated based on population.
| Occupancy | Basis of calculation |
|---|---|
| Residential building | 5 persons per tenement |
| Other buildings | Number of persons based on occupant load and the area of floors given in the code's table |
Five persons per tenement is a flat assumption, applied to every flat in the building regardless of its size or the number of bedrooms in it.
For a scheme of large units that is generous. For a scheme of small units, particularly one taking the EWS and LIG incentive, where at least 40 percent of tenements must be 30 sq m of carpet or less, it is the same figure applied to a very different household. And for a mixed scheme it means the calculation does not distinguish between the two.
The figure is a design basis, not a promise of supply. What actually arrives at a tap depends on the municipal connection, the storage provided and the distribution, none of which this regulation settles.
The tank, and where the water goes
Two short provisions elsewhere in the code cover the ends of the same system.
Chapter 9, Regulation 9.21, Overhead Tanks requires every overhead water storage tank to be maintained in a perfectly mosquito proof condition by providing a properly fitting hinged cover, and requires every tank more than 1.5 m in height to be provided with a permanently fixed iron ladder. Both are maintenance-facing requirements: a tank nobody can safely reach is a tank nobody cleans.
Chapter 9, Regulation 9.25, Septic Tanks requires every building, or group of buildings together, to be either connected to a drainage system or provided with a sub-soil dispersion system in the form of a septic tank of suitable size and technical specifications, with modern methods of disposal specified by Government bodies such as NEERI also permissible.
Chapter 12, Regulation 12.6, Drainage and Sanitation Requirements carries the drainage and sanitation requirements alongside these.
Related rule cards
- Compound walls, wells and septic tanks
- The green features that are compulsory
- What the code guarantees inside your flat
Where the filings come in
MahaRERA does not publish a project's water calculation or its tank capacity. It does publish the total unit count, which is the multiplier this regulation applies, and that is free to read.
Every filing at reragenie.com carries the filed land area, the total and sold units, the buildings and their floors, the promoter's extension history with the reasons given, and any complaints or litigation with case numbers.
ReraGenie's buyer report, Rs 499, reads one project's full filing and the documents behind it, including progress on shared amenities as well as on buildings, and includes a project watch for 90 days.
Source: Unified Development Control and Promotion Regulations for Maharashtra, UDCPR as updated 30 January 2025. Sanctioned under the Maharashtra Regional and Town Planning Act, 1966.
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