How to Choose the Right Water Tank Size (and Type) for Your Home: A Practical Buying Guide for Indore

Think of a water tank as your home's tiffin box. When you pack a tiffin, you do two sums in your head: how many people are eating, and how long the food has to last until the next meal. A water tank works exactly the same way. It has to hold enough water for everyone in the house until the next time the tap line "refills" it.

So the whole decision comes down to two questions. One: how many people live in your home? Two: how often does water actually arrive in your area — every day, on alternate days, or only for an hour or two? In much of Indore, municipal Narmada supply reaches core-city areas on alternate days or for limited hours, so the tiffin box has to be packed for more than one meal.

There is also a smaller third question — which box? A steel dabba keeps food better than a thin polythene bag; likewise, a 3-layer or 4-layer tank with a black middle layer keeps water cleaner than a cheap translucent one, because sunlight cannot get in and grow algae.

One-line verdict: allow roughly 150 litres per person for every day you must last between refills — so a family of four with alternate-day supply needs about 1,000–1,500 litres, in a 3-layer ISI-marked vertical tank.

How much water a household actually uses (NBC 2016 / CPHEEO)

Indian plumbing design does not guess demand; it uses per-capita norms. The National Building Code of India 2016 (Part 9) works with 150–200 litres per capita per day (LPCD) for residences in cities with population above one lakh, of which roughly 45 LPCD is for toilet flushing and the balance for drinking, cooking, bathing and washing. The CPHEEO benchmark for fully sewered cities, and the figure NBC permits where supply is constrained, is 135 LPCD. For hostels and boarding houses, NBC works with about 135 LPCD total (90 domestic + 45 flushing).

For household tank sizing in Indore, 135 LPCD is a realistic planning figure; use 150–180 LPCD if the house has multiple flushing toilets, a washing machine run daily, and a small garden or car washing.

The sizing formula, and why buffer days decide everything in Indore

The formula is one line:

Tank capacity (litres) = number of persons × LPCD × days of buffer

The "days of buffer" term is where Indore differs from a 24x7-supply city. Indore draws its municipal water mainly from the Narmada, lifted roughly 70 km to the city. Smart City Indore's own water-supply documentation records that the core ABD (Area Based Development) zone receives piped water on an alternate-day basis, supplemented by borewells run only 2–3 hours a day. A 24x7 pilot began in a handful of colonies in 2019, but most localities across Indore, Dewas, Ujjain, Pithampur, Dhar and Mhow still receive supply either on alternate days or for a fixed one-to-two-hour window, and borewells run dry in peak summer.

Practical buffer values:

• Daily, reliable supply: 1 to 1.5 days
• Alternate-day supply (common in Indore): 2 to 2.5 days
• Erratic supply or borewell-dependent: 3 days, split between an underground sump and an overhead tank

The standard split is: underground sump holds the bulk (it receives whatever comes, whenever it comes), and the overhead tank holds about one day's use, refilled by pump. Standard market capacities are 500, 750, 1,000, 1,500, 2,000, 3,000 and 5,000 litres — always round your calculation up to the next standard size.

IS 12701 and what the layers actually do

Plastic overhead tanks in India are governed by IS 12701:1996 — Rotational Moulded Polyethylene Water Storage Tanks. The standard requires food-grade polyethylene that imparts no taste, odour, colour or toxicity to water; limits antioxidants to 0.3 per cent; requires 2.0–3.0 per cent well-dispersed carbon black in outdoor tanks for UV protection; covers cylindrical vertical tanks from 200 to 20,000 litres and rectangular loft tanks from 150 to 500 litres; and specifies minimum wall thickness rising from 3.0 mm at 200 L to 13.2 mm at 20,000 L. Every compliant tank must be marked with the maker's name, net capacity, batch number and year. Look for the ISI mark — an unmarked bargain tank may be moulded from unknown recycled plastic.

What the layer counts mean in practice:

• 2-layer: outer UV-stabilised layer plus an inner layer. Basic outdoor protection; sunlight can still penetrate lighter shades, so algae is possible.
• 3-layer: the workhorse. Outer UV-resistant layer (often white or coloured to reflect heat), an opaque black middle layer that blocks sunlight completely — this is the anti-algae layer — and an inner food-grade layer in contact with water. Prince's Storefit range, for example, is built exactly this way: white UV outer, black middle, food-grade inner.
• 4-layer: adds either a foam/insulating layer or an anti-microbial inner coating over the 3-layer structure, keeping water noticeably cooler on a west-facing Indore roof in May.
• 5-layer foam-insulated: a foam core sandwiched inside the wall — the "thermos flask" of tanks. Best water-temperature stability and stiffness, at the highest price.

For most homes, 3-layer is the value sweet spot; pay for 4-layer or foam insulation when the tank sits in full sun and summer tap water becomes uncomfortably hot.

Vertical, horizontal or loft: choose by location, not looks

• Vertical cylindrical tanks are the default for open roofs: best litres-per-rupee, full range of sizes, and the format IS 12701 is written around.
• Horizontal tanks suit spots with height limits — under a staircase landing, on a structural frame, or where wind exposure makes a tall tank risky. You pay more per litre for the same capacity.
• Loft tanks (150–500 L, rectangular) fit above bathrooms and kitchens inside the house, typically as a secondary tank feeding a geyser or one bathroom. Indoor-rated loft tanks are marked "for indoor use only" under IS 12701 and must not be used on open roofs, as they lack the carbon-black UV package.

Roof loading: where a full tank can and cannot sit

Water weighs 1 kg per litre, so a 1,000 L tank is roughly one tonne once you add the tank's own 25–35 kg; a 2,000 L tank is over two tonnes. Because the tank stands on a small footprint (about 1 m² for a 1,000 L vertical), the local pressure works out to around 10–11 kN/m² — while a typical residential RCC slab is designed for an imposed (live) load of only about 2 kN/m² per IS 875 (Part 2). Rules that follow:

1. Place tanks directly over or immediately beside beams and columns — ideally at a corner or edge where two beams meet — never at the middle of an unsupported slab span.
2. For 2,000 L and above, or any battery of multiple tanks, build a short masonry or RCC platform that spreads the load onto beams, and have a structural engineer confirm the slab for older buildings.
3. Two 1,000 L tanks placed over two different beam junctions load the structure more kindly than one 2,000 L tank in one spot — and give you a standby when one is being cleaned.

All figures indicative, mid-2026, may vary by brand, city, dealer discount and litre class. Published brand MRPs run higher; negotiated street and wholesale prices run lower.

For reference, published 2025–26 price lists show branded 3-layer 1,000 L tanks (Supreme, Vectus, Sintex, Plasto) clustering between ₹6,000 and ₹12,000 at MRP, and branded 4-layer 1,000 L tanks between roughly ₹9,000 and ₹15,500.

Extras to budget beyond the tank:

Puranmal Sons & Ceramix Syndicate is a wholesale supplier of water tanks, plumbing pipes and fittings in Indore, stocking ISI-marked 2-layer to foam-insulated tanks from 200 L loft sizes up to 5,000 L, serving Indore, Dewas, Ujjain, Pithampur, Dhar and Mhow. If you are unsure between two sizes or want current prices for a specific brand and layer type, we will work the calculation with you before you buy. Call 95222-20983 or visit us at 254, Jawahar Marg, Rajmohalla, Indore — send us your family size and supply schedule, and we will suggest a size and quote the same day.