How Often Should You Clean Your Water Tank?

Why Tank Cleaning Matters

In India, most homes store water in rooftop or underground tanks. Over time, sediment, algae, bacteria, and insects accumulate inside the tank. Even if your municipal supply is clean, a dirty tank can contaminate the water before it reaches your tap.

Studies by the National Environmental Engineering Research Institute (NEERI) have found that improperly maintained water tanks are a significant source of waterborne diseases in Indian cities.

How Often Should You Clean?

General recommendation: Every 6 months.

For different situations:

• Underground tanks: Every 3–4 months — more prone to contamination from seepage, insects, and rodents
• Rooftop tanks: Every 6 months — better protected but exposed to sunlight (promotes algae growth)
• Plastic tanks: Every 6 months — smooth surface reduces buildup
• Concrete tanks: Every 3–4 months — rough surfaces harbour more bacteria
• Monsoon season: Clean before and after monsoon (April and October) — rainwater runoff increases contamination
• Water from tankers: Clean monthly if using tanker water regularly — tanker water quality is unpredictable

Signs Your Tank Needs Cleaning

Do not wait for the scheduled date if you notice:

• Visible sediment: Sand, rust, or dirt at the bottom of your taps
• Algae growth: Green slime inside the tank or green tint in water
• Bad odour: Rotten egg smell (hydrogen sulphide) or musty odour
• Bad taste: Metallic, earthy, or chemical taste
• Discolouration: Yellow, brown, or cloudy water
• Insect debris: Mosquito larvae or dead insects in tank
• Unexplained illness: Family members experiencing diarrhoea or stomach issues
• Slippery tank walls: Biofilm formation — a layer of bacteria

The Cleaning Procedure

Step 1: Empty the tank

• Turn off the inlet valve
• Drain all water through the outlet or use a pump
• Keep a small amount of water at the bottom for cleaning

Step 2: Scrub the interior

• Wear rubber gloves and boots
• Use a long-handled brush with stiff bristles
• Scrub all walls, floor, and corners
• Do NOT use soap or detergent — residue is hard to rinse

Step 3: Disinfect

• Prepare a bleaching solution: 1 part household bleach (5% chlorine) to 100 parts water
• Apply the solution to all interior surfaces using a brush or sprayer
• Alternatively, use chlorine tablets (available at medical stores — typically 4–6 tablets per 1000 litres)
• Let the solution sit for 30 minutes

Step 4: Rinse thoroughly

• Rinse with clean water at least 2–3 times
• Drain the rinse water completely
• Ensure no bleach smell remains

Step 5: Refill and flush

• Refill the tank
• Run all taps for 5 minutes to flush the pipes
• The water is now safe to use

Professional Tank Cleaning

Hire a professional tank cleaning service every 6–12 months. Costs in Indian cities range from ₹500–₹2,000 for a standard 1000-litre tank. Professional services use high-pressure washers, industrial vacuums, and food-grade disinfectants.

Prevention Tips

• Install a mesh cover on the inlet and overflow pipes to prevent insects and debris entry
• Keep the tank lid tightly sealed
• Use a dark-coloured tank to prevent algae growth (blocks sunlight)
• Install a first-flush diverter if collecting rainwater
• Check the tank interior monthly through the inspection hatch

Key Takeaways

• Clean underground tanks every 3–4 months; rooftop tanks every 6 months
• Clean before and after monsoon season
• Use bleach solution (1:100 ratio) for disinfection — no soap or detergent
• Hire professional services every 6–12 months for deep cleaning
• Install mesh covers and seal lids to prevent recontamination between cleanings