Size of water tank in residence as per NBC

The National Building Code (NBC) of India, 2016 provides detailed guidelines for estimating water supply requirements for residential buildings. Below is a summarized reference for calculating water tank size based on the population, type of dwelling, and water consumption:

Population Estimation per Dwelling Unit

1. 1-bedroom dwelling unit: 4 persons
2. 2-bedroom dwelling unit: 5 persons
3. 3-bedroom dwelling unit: 6 persons
4. 4-bedroom dwelling unit and above: 7 persons
5. EWS dwelling unit: 4 persons
6. Studio apartment: 2 persons

Water Requirement

• Domestic Needs: 70 to 100 liters per head per day (lphd) for urban communities.
• Non-domestic Needs (Flushing): Additional requirement based on the type of building occupancy.
• Total Requirements:
  • Small communities (<20,000 population): 70–100 lphd.
  • Medium communities (20,000–100,000 population): 100–135 lphd with a full flushing system.
  • Large communities (>100,000 population): 150–200 lphd with a full flushing system.
    • For MIG, LIG, and EWS categories: 135 lphd may be used instead of 150–200 lphd.

Example Calculation

For a 3-bedroom dwelling unit:

• Population: 6 persons
• Water consumption: Assume 135 lphd (domestic + non-domestic needs for medium population communities).
• Total Daily Requirement:

To calculate the water tank size, consider the following:

1. Daily Requirement: Size the tank to store at least one day of water supply (810 liters for the example above).
2. Buffer Storage: Add a buffer for emergencies or unforeseen demand.

Size of Under Ground Water tank in cuft

To calculate the size of a water tank in cubic feet (cuft), follow these steps:

1. Convert Liters to Cubic Feet: 1 liter = 0.035315 cubic feet
   Therefore, the volume in cubic feet (cuft) = Volume in liters × 0.035315.
2. Include a Buffer:
   If a buffer of four days is needed, calculate the adjusted volume:
   Adjusted volume = Daily requirement × (1+4).

Example Calculation:

Assume a 3-bedroom dwelling unit with a daily requirement of 810 liters and a four day buffer.

1. Convert liters to cubic feet: 810 liters×0.035315=28.61 cuft.
2. Add a 4 day buffer: 28.61 cuft×5=143.05 cuft. = 6ft X 6ft X 4ft

Result:

The under ground water tank size should be approximately 6ft X 6ft X 4ft for a 3-bedroom dwelling unit with a four day buffer.

Notes

1. These figures are general guidelines and may vary depending on local water availability and conditions.
2. For plotted developments, population estimation and tank sizing should consider the specific number and type of dwelling units.