How to Clean a Water Tank at Home

First: should you do it yourself?

DIY cleaning is reasonable for a small overhead plastic tank (up to about 1,000 litres) that you can reach and work on safely. Don't attempt it yourself if:

• The tank is underground. Sumps are confined spaces where the air can be unsafe and getting out is difficult. People have been seriously hurt entering sumps. Leave these to professionals.
• You'd have to climb inside a large tank or work on a high, narrow platform or sloping roof.
• There's heavy sludge — you'll struggle to remove it without pushing it into your pipes.
• Something has died in the tank or sewage may have entered. This needs thorough cleaning and disinfection.

What you'll need

• A soft brush or long-handled soft scrubber (no wire brushes on plastic).
• Clean sponges and cloths, and two or three buckets.
• A mug or small pan for scooping, and a wet-dry vacuum if you have one.
• Rubber gloves and non-slip footwear.
• A torch.
• A household disinfectant intended for drinking-water use if you plan to disinfect (see step 6).
• A second person to help and keep watch.

Step-by-step

1. Plan the timing

Choose a morning when the tank level is low. Switch off the motor that fills the tank and close the inlet valve. Store water in buckets for the next few hours.

2. Drain the tank — but not through your pipes

Use the water for cleaning floors, toilets or the garden by opening taps. Stop when only the bottom few inches remain: this layer contains most of the sediment, and you don't want it running into your plumbing.

3. Remove the sludge

Scoop out the remaining dirty water and sludge with a mug into a bucket, or use a wet-dry vacuum. Wipe the floor with a sponge, wringing it into a bucket. Take your time — this is the most important step.

4. Scrub the walls and lid

Scrub the walls, floor, corners and the underside of the lid with a soft brush and clean water. Pay attention to the inlet, the float valve and the overflow. Don't use detergent powders, phenyl, acid or bleach-based toilet cleaners — residues are hard to rinse out and some are toxic.

5. Rinse

Rinse the walls with clean water and remove the rinse water by scooping or vacuuming. Repeat until it runs clear.

6. Disinfect (carefully)

If you choose to disinfect, use a product specifically intended for drinking water, follow the label dose exactly, and observe the contact time. Then rinse thoroughly. Too much disinfectant can make the water unpleasant or unsafe; too little does nothing. Our guide on water tank cleaning chemicals explains what's appropriate.

7. Refill and flush

Close the lid securely, open the inlet and switch the motor back on. Once the tank has some water, run each tap for a minute to flush loosened debris from the pipes.

Common DIY mistakes

• Flushing sludge through the taps. It settles in pipes, geysers and RO filters.
• Scratching plastic tanks with wire brushes or abrasive powders.
• Using cleaning chemicals not meant for drinking water.
• Cleaning only the rooftop tank and refilling it from a dirty sump.
• Working alone at height or inside a tank.

When to call professionals

Professional cleaning adds vacuum de-sludging, thorough scrubbing of hard-to-reach areas, correctly dosed disinfection, photo proof — and nobody in your family climbing into a tank. A 1,000-litre rooftop tank costs ₹599, and a sump can be added in the same visit for a 10% discount. See overhead tank cleaning or underground tank cleaning.

When to call a professional instead

Home cleaning is fine for a small, lightly used rooftop tank. Call a professional if the tank has thick sludge, is underground or large enough that someone has to go inside, or if anyone at home has had stomach problems — working inside a tank is a safety risk without the right equipment.