How dirty is your water tank, really?

We've cleaned over 200 water tanks across Bangalore in the past year. Overhead tanks, underground tanks, residential, commercial, apartments. Every single one of them had something inside that the owner didn't know about.

Not because they were careless. But because water tanks are out of sight, and most people assume that if the water looks clear coming out of the tap, the tank must be fine. It's not.

What we actually find inside tanks

The most common thing we find is sediment. Layers of silt, mud, and fine sand that settle at the bottom of the tank over months. In Bangalore, where a significant percentage of water comes from borewells, this is especially bad. Borewell water carries high TDS (Total Dissolved Solids) and suspended particles that settle out once the water is still.

Sediment: the silent buildup

A 1,000-litre overhead tank in Bangalore can accumulate 2-5 kg of sediment in just 6 months. That's silt, dissolved minerals, rust from pipes, and organic matter all settling at the bottom. You can't see it from outside. You can't taste it in a glass of water. But it's there, and it's affecting water quality.

This sediment layer becomes a breeding ground for bacteria. In warm, stagnant water (exactly what the bottom of your tank is), bacterial colonies thrive. Studies show that uncleaned tanks can harbour coliform bacteria, E. coli, and other pathogens at levels well above safe limits.

Algae: more common than you think

If your tank gets any sunlight (and most overhead tanks in Bangalore do, especially PVC and plastic tanks), algae will grow. Even small amounts of light penetration through translucent tank walls is enough. We found visible algae in 68% of the tanks we cleaned.

Green algae on the walls, slippery biofilm coating the interior surfaces, and sometimes thick mats of growth near the water line. Algae itself isn't always dangerous, but it produces compounds that affect taste and odour, and it creates an environment where harmful bacteria thrive.

The Bangalore factor

Bangalore's water situation makes tank hygiene more critical than in many other cities. A large portion of the city relies on borewell water, which carries significantly higher sediment and mineral content than treated Cauvery water. Even in areas with Cauvery supply, intermittent supply means tanks sit with stagnant water for longer periods.

Add Bangalore's warm climate (bacteria love temperatures between 25-37 degrees Celsius, which is most of the year here), and you have ideal conditions for contamination in any tank that hasn't been cleaned in 6+ months.

How to know if your tank needs cleaning

The honest answer: if it's been more than 6 months, it needs cleaning. But there are some signs that indicate it's overdue:

• Slight discolouration or yellowish tint to tap water
• Musty or earthy smell from the water
• Reduced water pressure (sediment blocking outlets)
• Visible particles or grit in water
• Family members experiencing unexplained stomach issues

What proper cleaning looks like

A proper tank cleaning isn't a 20-minute rinse. It's a 6-stage process: drain, scrub, pressure wash, disinfect, rinse, and certify. Every surface needs to be scrubbed by hand, pressure washed, and treated with food-grade anti-bacterial agents. And the entire process should be documented with timestamped before and after photos.

If your current cleaner doesn't give you photos, you have no way of knowing what actually happened inside your tank. At HOW Cleaning, photo documentation is standard on every job. You see exactly what was in your tank and what it looks like after.