How Often Should You Clean Your Water Tank in Dhaka?

Almost every building in Dhaka stores water twice — once in an underground reservoir and once in an overhead tank. Both accumulate sediment from the supply, and both grow biofilm on their walls. Neither is visible from the tap, which is exactly why they get forgotten.

The recommended interval

For a typical Dhaka household, twice a year is the sensible minimum — once before and once after the monsoon. Buildings with heavy occupancy, an older reservoir, or a history of supply disruption should move to quarterly. If you cannot remember the last cleaning, it is overdue.

What builds up inside

Three things, in order of seriousness. Sediment settles as a fine silt layer on the tank floor, thickening every month. Biofilm forms a slick layer on the walls where bacteria live and multiply — it is the reason a tank can look reasonably clear and still make people ill. And in overhead tanks where any light penetrates, algae grows and gives water a distinct earthy taste and smell.

Tanks with damaged or missing covers also collect insects, lizards, leaves and street dust. That is one of the most common findings when we open a tank that has not been inspected in years.

What a proper cleaning involves

• Isolating and fully draining the tank
• Manual removal of sludge from the floor
• Brushing every wall, the floor and the underside of the cover
• Wet-vacuum extraction of the residual water and sediment
• High-pressure washing of all internal surfaces
• Food-grade chlorine disinfection at the correct dosage and contact time, then rinse
• Inspection of walls, joints, cover and vent screens, with photographs

Any service that skips the vacuum stage is leaving sediment in suspension to resettle. Any service that skips disinfection has cleaned the tank without making the water safe.

Warning signs you should not wait out

Cloudy water after supply resumes. A musty or earthy smell. Visible particles in a glass left to stand for a few minutes. Repeated stomach complaints in the household with no other explanation. Blocked tap aerators or a shower head that has lost pressure. Any one of these means the tank should be opened and inspected now rather than at the next convenient time.

What it costs to ignore

Beyond the health risk, sediment shortens pump life, blocks aerators and filters, stains sanitary ware and clogs washing machine inlet screens. Tank cleaning is one of the few maintenance jobs that pays for itself in equipment life alone, before you count the health benefit at all.

If you share a reservoir with other flats

In most Dhaka apartment buildings the underground reservoir is shared and therefore nobody individually owns the problem. The practical fix is for the building committee to put it on a documented twice-yearly cycle with photographs circulated to residents. That single change settles the recurring argument about whether it was really done, and costs each flat very little.