HOW TEMPERATURE IMPACTS THE QUALITY OF WATER — A ROOFTOP REALITY

Rooftop plastic water tanks are norm, in most Indian homes. They're convenient, require minimal maintenance and they are economical. However, there's a silent issue that we often fail to notice — how the rising of ambient temperature affects the quality of water, stored in these tanks.

How much does the water heat up?

During peak summer months, the temperature of rooftops on Indian homes can reach 40–60°C or even more. Under such harsh sunlight, the black or dark-colored plastic tanks absorb and retain heat, causing the water inside to rise to over 45°C — in most cases exceeding the temperature of a hot shower.

Discomfort is just one aspect of this excessive heating of the water; it actually poses serious risks to the quality of water and health.        

How does the high temperature affect the stored water?

1. Microbial Growth

Warm water is generally a breeding ground for bacteria, algae, and fungi, particularly for the tank, if it is not cleaned regularly. Studies have shown that bacteria like E. coli multiply faster in warmer conditions specifically within a range of temperatures around 37°C [1]. This effect can lead to:

§ Skin infections

§ Eye irritation

§ Gastrointestinal issues (if water is used for cooking or brushing)

2. Chemical Leaching from Plastic

Heat and exposure to UV radiation for long duration leads to degradation of plastic tank walls which releases microplastics and additives like BPA (Bisphenol A) into the water [2]. Ingestion of these chemicals can cause Hormonal disruption and numerous other health complications.

3. Dissolved Oxygen: 

Warm water holds less dissolved oxygen than cool water. This effect becomes more acute for water remaining stagnant for long hours. Lower oxygen levels can also accelerate the decomposition of organic matter, further degrading water quality, for example causing unpleasant odour and taste.

4. pH change:

Warmer water often shows a slight decrease in pH due to the accumulation of carbon dioxide [3]. Changes in pH can impact the solubility of certain substances and even leaching of certain chemicals from the wall of the water tank [4]. 

5. Increased evaporation loss

High temperatures increase evaporation from open or loosely covered tanks, reducing available water and putting more strain on supply — especially in water-scarce regions.

What can be done?

The most effective solution is preventing the tank from heating up in the first place.

Here’s how:

Choose light-colored tanks or apply UV-protective coatings.

Keep tanks well-covered and cleaned regularly.

Insulate your water tank using a reflective, radiative, and thermally insulating sheet.

Conclusion

Hot weather and rooftop tanks don't go well together — unless you take action. Controlling the temperature of stored water is not just a comfort issue; it's a health necessity. Insulating your tank is a small investment with huge daily returns.

References

1. C.-Y. Yang, M. Erickstad, L. Tadrist, E. Ronan, E. Gutierrez, J. Wong-Ng, A. Groisman, Aggregation Temperature of Escherichia coli Depends on Steepness of the Thermal Gradient, Biophysical Journal 118, 2816–2828, 2020.

2. A. T. Ahmed, M. Emad, M. A. Bkary, Impacts of temperature alteration on the drinking water quality stored in plastic bottles, Applied Water Science, 11, 167, 2021.

3. J.-L. Crolet, M. R. Bonis, pH Measurements in aqueous CO2 solutions under high pressure and temperature, Corrosion, 39(2):39-46, 1983.

4. A. R. Hammodat, S. Nassar, Md M. Mortula, M. Shamsuzzaman, Factors affecting the leaching of micro and nanoplastics in the water distribution system, Journal of Environmental Management 345 (2023) 118779.