Why Getting Your Water Tank Size Right Matters
An undersized tank leaves your family short of water during supply gaps. An oversized tank, on the other hand, wastes money, takes up valuable space, and can cause water to stagnate if not refilled regularly.
In Kerala, where municipal water supply is often limited to a few hours a day, the right household water tank is not a luxury ,it is essential infrastructure. The same applies to industrial water tank installations in factories, hospitals, and commercial buildings, where consistent water availability directly affects operations.
Choosing from a trusted brand matters too. ISO certified water tanks, like those manufactured by Sintex ,one of India’s foremost water tank manufacturers in India ,are tested to international standards for material safety, UV resistance, and leak-proof construction. Essjay Enterprises stocks the complete Sintex range, ensuring you always get a certified, quality product
How to Calculate Water Tank Size ,The Formula
The core formula for working out how to calculate water tank size is:
Tank Capacity (litres) = Daily Water Requirement × Number of Family Members × Buffer Days
Daily water requirement per person: As per CPHEEO (Central Public Health and Environmental Engineering Organisation) standards for India, the recommended figure is 135 litres per person per day for urban households. This covers drinking, cooking, bathing, toilet flushing, and general household use.
Buffer days: This is the number of days you want your tank to last if supply is cut off. In most parts of Kerala, a 2-day buffer is advisable. In areas with frequent dry spells or irregular supply, opt for 3 days.
Worked Example
| Scenario | Calculation | Recommended Tank Size |
| 4 members, 2-day buffer | 135 × 4 × 2 | 1,080 L → choose 1,000–1,500 L tank |
| 6 members, 2-day buffer | 135 × 6 × 2 | 1,620 L → choose 2,000 L tank |
| 4 members, 3-day buffer | 135 × 4 × 3 | 1,620 L → choose 2,000 L tank |
Water Tank Size Calculator
Find out exactly how to calculate water tank size for your home, flat, or commercial building — using the official CPHEEO formula.
ISO certified water storage tanks for homes & industry.
Standard reference: 135 L/person/day as per CPHEEO (Central Public Health and Environmental Engineering Organisation), Government of India.
Disclaimer: This calculator provides a guideline estimate. Actual requirements may vary based on local supply conditions, pipe pressure, and usage patterns. Consult Essjay Enterprises for a personalised recommendation.
Overhead Tank vs Underground Sump ,How to Calculate Water Tank Size for Each
Most Kerala homes use a two-tank system: a large underground sump that stores the day’s supply, and a smaller overhead tank that feeds taps by gravity.
Underground Sump Tank: Size it to hold 1–2 days of total household requirement. For large water storage containers underground, 3,000–10,000 L is the common range for residential use.
Overhead Tank: Typically sized to hold half a day to one full day of usage. Sintex water tanks in the 500 L–2,000 L range are the most popular choice for overhead installation in Kerala homes.
Combined calculation example (6-member household):
- Sump: 135 × 6 × 2 = 1,620 L → choose a 2,000 L sump
- Overhead: 135 × 6 × 0.5 = 405 L → choose a 500 L overhead tank
Special Considerations for Water Storage Tanks in Kerala
Kerala’s unique geography and climate create conditions that affect how you should calculate water tank size:
1. Monsoon vs summer planning Even during heavy monsoon, municipal supply can be irregular. Size your tank for the dry season, not the rainy season.
2. Well and borewell supplementation Many Kerala homes combine municipal supply with well water. If your well runs during summer, you may need less tank buffer ,but always plan for the worst-case scenario.
3. Rainwater harvesting integration Kerala’s annual rainfall is among the highest in India. If your home has a rainwater harvesting setup, you can reduce your tank size slightly and use the rainwater as a supplementary source.
4. Roof load capacity A 1,000 L water tank weighs approximately 1,000 kg when full. Always check your terrace load-bearing capacity before installing large water storage containers overhead. Essjay Enterprises’ installation team can advise on this.
5. Water supply hours per day If your area receives only 1–2 hours of municipal supply daily, increase your buffer days to 3–4 to be safe.
How to Calculate Water Tank Size for Commercial and Industrial Use
For commercial properties, hospitals, hotels, and factories, the standard household formula needs adjustment.
Industrial water tank sizing formula:
Capacity = Daily operational water use × 1.5 (safety factor) × Buffer days
For industrial water tank installations, also factor in:
- Fire-fighting reserve (typically 10,000–50,000 L depending on building type)
- Peak-load days (festivals, busy seasons)
- Water quality requirements (some industries need separate storage for process water)
Sintex, one of India’s leading water tank manufacturers in India, manufactures industrial-grade large water storage containers from 5,000 L to 1,00,000 L. Essjay Enterprises supplies and installs these for government, private, and commercial projects across Kerala.
Sintex Water Tanks ,Available Sizes and Key Features
Sintex water tanks are the benchmark for quality among household water tanks and industrial water tank solutions in India. Here is what makes them the right choice:
- ISO certified manufacturing to international quality standards
- Triple-layer construction (outer UV-resistant layer, insulating foam layer, food-grade inner layer)
- Available in sizes from 100 L to 1,00,000 L ,covering household water tanks to large water storage containers for industrial use
- Made from virgin-grade food-safe polyethylene
- Approved by leading water tank manufacturers India quality bodies
Popular Sintex tank sizes available at Essjay Enterprises:
| Use Case | Recommended Sintex Size |
| Studio / 1BHK | 500 L |
| 2–3 BHK family home | 1,000 L |
| Large family / villa | 2,000 L – 3,000 L |
| Small commercial | 5,000 L – 10,000 L |
| Industrial water tank | 20,000 L – 1,00,000 L |
Common Mistakes When Calculating Water Tank Size
- Using the wrong per-person figure ,Many people estimate 50–80 L per person. The actual usage in a Kerala home is closer to 135 L.
- Not accounting for supply gaps ,Assuming daily refill leads to undersizing. Always use a 2–3 day buffer.
- Ignoring roof load ,Large water storage containers are heavy. Structural checks are non-negotiable.
- Skipping the sump calculation ,Treating overhead tank size as the only calculation misses the sump, which often holds 3–5x more water.
- Choosing non-ISO certified tanks ,Non-certified tanks may leach chemicals into drinking water. Always insist on ISO certified Sintex water tanks.
- Buying the cheapest option ,Lower-cost tanks from unverified water tank manufacturers India often lack UV protection and crack within 2–3 years.
Now that you know how to calculate water tank size for your home, the next step is choosing the right tank. Essjay Enterprises ,Kerala’s leading distributor of ISO certified Sintex water tanks since 2001 ,carries the full range of household water tanks, large water storage containers, and industrial water tank solutions to match any requirement.
Whether you need a 500 L overhead tank for a flat or a 50,000 L industrial water tank for a factory, our team will help you select, deliver, and install the right solution.
FAQ
How do I calculate water tank size for my home?
Use the formula: Tank Capacity (L) = 135 litres × number of family members × number of buffer days. For a family of 4 with a 2-day buffer, you need at least 1,080 litres. Choose the nearest standard Sintex tank size ,1,000 L or 1,500 L.
What is the right water tank size for a family of 4 in Kerala?
A 1,000–1,500 litre household water tank is ideal for a 4-member family with normal municipal supply. If supply is irregular, go for 2,000 L.
What is the difference between a sump tank and an overhead tank?
A sump is a large underground tank that stores the day’s supply; an overhead tank is a smaller tank on the terrace that distributes water by gravity. Most Kerala homes need both. Size your sump 3–5x larger than your overhead tank.
Are Sintex water tanks ISO certified?
Yes. Sintex water tanks are ISO certified and manufactured to international quality standards. They use food-grade virgin polyethylene and are approved for potable water storage.
How do I calculate industrial water tank size?
Multiply daily operational water consumption by 1.5 (safety factor) and then by the number of buffer days. Add a fire reserve if required by building codes. Essjay Enterprises supplies large water storage containers for industrial water tank applications across Kerala.
How much does a 1,000-litre Sintex water tank weigh when full?
Approximately 1,000 kg (1 tonne), since water weighs 1 kg per litre. Always verify your terrace can support this load before installation.
Where can I buy Sintex water tanks in Kerala?
Essjay Enterprises is Kerala’s authorised Sintex water tank distributor, serving customers since 2001. We supply water storage tanks in Kerala for residential, commercial, and industrial applications. Contact us at +91 9447751837 or visit essjayenterprises.com.
What is the best water tank size for a 3-bedroom house in Kerala?
For a typical 3BHK with 4–5 family members, a 1,500–2,000 litre household water tank for overhead use, combined with a 3,000 L sump, is the standard recommendation in Kerala.
