Bathroom Water Tank Calculator
Enter how many people and bathrooms you have, how you bathe, and how many days of reserve you want. Get the overhead tank and sump size your home needs. Indicative India 2026 (~135 L/person/day norm) — always confirm for your local supply.
Your home & usage
Bucket ≈ 40 L/person/day, shower ≈ 70 L/person/day for bathing.
Per person we count bathing, flushing (~30 L) and clothes washing (~20 L), plus ~15 L/day per bathroom for cleaning. Your home draws about 145 L/person/day. The overhead tank is sized for roughly one day; the sump holds the rest of your reserve.
Recommended total storage
0 L
for 1 day of reserve at 0 L/day demand
Overhead tank
750 L
~one day's draw
Underground sump
Optional
not needed at this reserve
Daily demand
610 L
4 people + 2 baths
Per person
145 L
per person / day
Daily demand by use (litres/day). Indicative — confirm against your actual metered use.
Plan your tank & pump
Get an overhead/sump split and pump advice from DesignAI.
Estimates are indicative and use ~135 L/person/day as a domestic norm (BIS IS 1172 / CPHEEO guidance) — a bathroom-only draw can be lower and real use varies with habits, guests, gardens and supply reliability. Round up to a stocked tank size, keep the overhead tank within your roof slab's safe load, and confirm sizing, pump and plumbing with a local plumber before buying.
Frequently asked questions
- How does the bathroom water tank calculator size my storage?
- It estimates your home's daily water demand, then multiplies by the reserve days you want. Per person it counts bathing, flushing and clothes washing, plus an optional kitchen and utility allowance, and adds a small daily cleaning figure per bathroom. This follows the roughly 135 litres per person per day domestic norm used in Indian planning. The overhead tank is sized for about one day's draw and the underground sump holds the rest of your reserve.
- What inputs do I need and what values should I use?
- Enter the number of people, the number of bathrooms, whether you mostly bathe with buckets or showers, and how many reserve days you want. Bucket bathing uses far less water than a shower, so pick the one your household actually uses. For most homes with fairly reliable supply a one-day reserve is enough; choose two or more days if your area faces frequent supply gaps.
- How accurate is this and what should I verify?
- Treat the result as an indicative planning figure, not a precise specification. Real use varies with habits, guests, gardens and supply reliability, and a bathroom-only draw can be lower than the full-home norm. Round up to a stocked tank size, keep the overhead tank within your roof slab's safe load, and confirm the final sizing, sump split, pump and plumbing with a local plumber or engineer per NBC 2016 Part 9 before buying.
Related Guides — Deep-dive reading
Water Supply Systems in India: How Water Reaches Every Tap in Your Home
The complete map of how water gets into an Indian home and out to every fixture — the sources it comes from, the sump-pump-overhead-tank storage model that buffers intermittent supply, how gravity and pressurised distribution differ, and the demand figures that size the whole thing.
PlumbingWater Consumption Estimation for Buildings: LPCD Norms, Occupancy & End-Use Breakdown
How to estimate a building's daily water demand from its occupancy and NBC per-capita norms, break it down by end use, and turn that number into the foundation for sizing water supply, storage and sewage systems.
Sewage Treatment PlantsBathroom Water Supply India: Cold & Hot Feed, Pipe Sizing, Pressure & Booster Pumps (2026)
How water actually reaches your fixtures in an Indian home — gravity-fed cold from the overhead tank, hot from the geyser, the pipe sizes that decide whether your shower gushes or dribbles, isolation valves at every fixture, booster pumps and hard-water protection, all mapped to IS 1172.
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