How to Choose the Right Water Tank Size for Your Home

Buying a water tank looks simple until you stand in front of a dealer and hear questions like "how many layers?", "ISI or regular?" and "loft or overhead?". This guide walks you through the decisions step by step.

Step 1: Calculate your daily water need

A practical rule of thumb for Indian households is 135 litres per person per day. This covers drinking, cooking, bathing, washing and cleaning.

• 2–3 member family: 300–500 litres
• 4–5 member family: 500–750 litres
• 6–8 member family (or duplex): 1000 litres
• Joint families / small commercial use: 1500–2000 litres

If your water supply is irregular, size the tank for 1.5 to 2 days of usage so a missed supply day never leaves you dry.

Step 2: Choose the number of layers

Tank walls are made in multiple layers, and each layer has a job:

• 2-layer tanks are economical and fine for shaded installations.
• 3-layer tanks add a black middle layer that blocks sunlight, which stops algae growth — the most common choice for rooftops.
• 4-layer and 5-layer tanks add a foam or insulation layer that keeps water noticeably cooler in summer, plus extra strength for large capacities.

For a typical open rooftop under the Indian sun, we recommend at least a 3-layer tank; if summer water temperature bothers you, go for a foam-insulated model like the BAISHALII Strong or Royal series.

Step 3: Check the placement

• Overhead (rooftop): the standard choice — make sure the tank sits on a flat RCC platform slightly wider than its base.
• Loft tanks: low-height tanks designed to slide into bathroom or kitchen lofts; ideal for apartments.
• Underground tanks: built with thicker ribbed walls to handle soil pressure; used as sumps for storing municipal supply before pumping up.

Never place a standard overhead tank underground — the wall construction is completely different.

Step 4: Look for food-grade and ISI marks

The inner layer that touches your water should always be 100% virgin, food-grade polyethylene. If you want certified assurance, choose an ISI-marked tank (IS 12701) — these are tested for wall thickness, impact strength and capacity accuracy.

Quick recommendation table

The BAISHALII line-up

BAISHALII water tanks come in 15 models across Strong, Royal, Regular, Diamond, ISI-marked, underground, septic and loft ranges — from 200 L lofts to 2000 L family tanks, all made with food-grade material. Explore the full range on our Water Tanks page, or reach out through the contact form and our team will help you size it right.