Water storage tanks ensure a continuous water supply despite intermittent municipal supply — a necessity in most Indian homes. The typical system is a two-tank arrangement: an underground tank / sump stores incoming municipal / borewell water at ground level, a pump lifts it to an overhead tank (OHT) on the terrace, and gravity then distributes it to all taps. Tanks are made of plastic (HDPE/LLDPE), RCC, FRP or stainless steel, and chosen by capacity, material and water quality.
Indian water tanks are governed by IS 12701 (Rotational Moulded Polyethylene Tanks) and IS 3370 (RCC liquid retaining structures). Major brands: Sintex, Plasto, Vectus, Sheetal, Penguin, Storefit, Supreme, Ashirvad, Selzer, RC Plasto.
Overhead tank height provides gravity pressure (~0.1 bar per metre of height). For good flow, the OHT base should be at least 3–5 m above the highest tap.
| Type | Location | Function |
|---|---|---|
| Overhead Tank (OHT) | Terrace / roof / stand | Gravity distribution |
| Underground Tank / Sump | Below ground | Bulk storage of incoming water |
| Loft Tank | Inside loft / small height | Small homes / flats |
| Ground-Level Tank | On ground | Storage + pump feed |
| RCC Underground Sump | Below ground (built) | Large storage (apartments) |
| Material | Pros | Cons |
|---|---|---|
| Plastic (HDPE/LLDPE Roto-Moulded) | Light, cheap, leak-proof, food-grade, easy install | UV degradation (low quality), algae if translucent |
| RCC (Reinforced Concrete) | Durable, large capacity, fire-safe | Cracks / leaks, costly, heavy, needs waterproofing |
| FRP (Fibreglass) | Strong, large, corrosion-proof | Costly |
| Stainless Steel | Hygienic, durable, premium | Expensive |
| Cast Iron / GI (old) | Strong | Rust, heavy (obsolete) |
| Layers | Description | Quality |
|---|---|---|
| Single Layer | One layer plastic | Basic / economy |
| 2 Layer | Outer + inner | Better |
| 3 Layer | UV outer + middle + food-grade inner | Standard recommended |
| 4 Layer | + Anti-microbial / insulation | Premium |
| 5 Layer | + Foam insulation (keeps cool) | Premium (hot climate) |
| Antibacterial / Black | Blocks light (no algae), antimicrobial inner | Best hygiene |
Black / opaque tanks prevent sunlight entry — stopping algae growth. Foam-insulated tanks keep water cooler in summer.
Plan storage as per occupants & usage. NBC norm: ~135 litres per person per day for residential (some use 90–150 L).
| Household | Daily Need (~135 L/person) | Recommended Storage (1 day OHT + 1 day sump) |
|---|---|---|
| 2 persons | ~270 L | 500 L OHT + 500 L sump |
| 4 persons | ~540 L | 1000 L OHT + 1000 L sump |
| 6 persons | ~810 L | 1000 L OHT + 1500 L sump |
| 8 persons | ~1080 L | 1500 L OHT + 2000 L sump |
| Apartment (per flat) | varies | 500–1000 L OHT + common RCC sump |
Common plastic tank sizes: 200, 300, 500, 750, 1000, 1500, 2000, 3000, 5000, 10000 L.
| Brand | Notable |
|---|---|
| Sintex | Market leader, 3/4/5 layer, antibacterial |
| Plasto (RC Plasto) | Multi-layer tanks |
| Vectus | Multi-layer, insulated |
| Sheetal | Multi-layer tanks |
| Penguin | Layered tanks |
| Supreme | Plastic tanks |
| Ashirvad (Aliaxis) | Premium tanks |
| Storefit / Selzer | Tanks |
| Kaveri / Aquatech | Regional tanks |
| Parameter | Plastic (HDPE) | RCC (Concrete) |
|---|---|---|
| Cost | Lower | Higher |
| Installation | Quick (ready-made) | Built on site (slow) |
| Leakage | Leak-proof (seamless) | Can crack / leak (needs waterproofing) |
| Weight | Light | Heavy (structural load) |
| Capacity | Up to ~10,000 L (single) | Very large possible |
| Hygiene | Food-grade, easy clean | Needs lining / cleaning |
| Lifespan | 15–25 yr | 30–50 yr |
| Best For | Homes, OHT | Large sumps, apartments, fire reserve |
| Pump Type | Use |
|---|---|
| Monoblock / Centrifugal | Sump to OHT (common) |
| Submersible Pump | Borewell / deep sump |
| Self-Priming Pump | Suction lift |
| Pressure Booster Pump | Boost tap / shower pressure |
| Openwell Submersible | Open sump |
Use an auto pump controller / level switch to fill OHT automatically & prevent dry running.
| Tank / Item | Cost (Rs) |
|---|---|
| 500 L (3 layer plastic) | 2,800 – 4,500 |
| 1000 L (3 layer) | 5,000 – 8,000 |
| 1000 L (4/5 layer / insulated) | 7,000 – 12,000 |
| 2000 L (3 layer) | 10,000 – 16,000 |
| 5000 L | 25,000 – 40,000 |
| 10000 L | 50,000 – 80,000 |
| RCC Underground Sump (per 1000 L, built) | 8,000 – 15,000 |
| Water Pump (0.5–1 HP) | 3,500 – 12,000 |
| Auto Pump Controller | 800 – 3,500 |
| Float Valve | 200 – 1,000 |
| Standard | Description |
|---|---|
| IS 12701 | Rotational Moulded Polyethylene Water Storage Tanks |
| IS 3370 (Part 1–4) | Concrete Structures for Storage of Liquids (RCC) |
| IS 10500 | Drinking Water Specification |
| IS 4985 | UPVC Pipes (connections) |
| IS 6587 | Reinforced Plastic (FRP) Tanks |
| IS 2065 | Code of Practice for Water Supply in Buildings |
| IS 1172 | Code for Water Supply, Drainage & Sanitation |
| NBC 2016 Part 9 | Plumbing Services (storage requirements) |
A well-designed two-tank system (underground sump + overhead tank) guarantees continuous water supply with gravity pressure. For homes, use ISI-marked 3-layer (or black antibacterial) food-grade plastic tanks, sized for about one day of storage each, placed high enough for good flow, with float valves, sealed vents and an auto pump controller. Clean tanks every six months for safe water.
Tanks supply water through CPVC / UPVC pipes (and GI risers) to faucets & showers, geysers, toilets, wash basins and kitchen sinks.