Water – How to prevent unpleasant smells and organisms in our water tank

health-and-safetywaterwater tank

There is an 8000 liter water tank on top of my house which provides water for the house.

Bacteria, fungi, algae, etc. often start developing in the tank, giving unpleasant smells, etc.

The water is ground water that we pump up there with our own pump.

The tank is made of concrete and covered with a steel lid.

Nobody is drinking or cooking with the water. It's used for stuff like laundry, showers, washing dishes, etc.

What can I do to prevent these unpleasant qualities of the water? It's very hot here (like 40 celsius in the shade), and the water tank is in the baking sun.

My landlord is unlikely to want to make any large investments. Therefore, cheap solutions are a plus.

Edit: Several answers have suggested chlorination, and it seems like the best option. But I live in rural India and it's difficult to find chlorine here. Bleach, though is readily available. Does it seem suitable? I've asked this as a separate question on Chemistry SE.

Best Answer

Even though you are not drinking this water, you are using it for showers and for washing dishes - so it probably needs to be treated nearly as seriously as drinking water.

The main methods are filtration, treatment with floculants, thermal treatment and chlorination.

Chlorination is a widely used method. Chlorine is present in most disinfected drinking-water at concentrations of 0.2–1 mg/litre

The World Health Organisation (WHO) publish "A toolkit for monitoring and evaluating household water treatment and safe storage programmes" (HWTS):

Several HWTS methods have been proven to significantly improve drinking-water quality in the laboratory and in field trials in developing countries . These HWTS methods include filtration, chemical disinfection, disinfection with heat (boiling, pasteurization) and flocculants/ disinfectants. In addition, a combination of these methods may be used to increase the efficacy of treatment.

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Note that WHO cite "low cost" as an advantage of chlorination.