1. The color of your tank, and
2. How often you pump water into the tank from your borehole.

Before we go further into these two factors, here’s something you may not know about your water storage tank: it begins to get dirty (with mostly sand and bacteria) as soon as it starts to receive water from your borehole.

Borehole water often contains particles – sand in particular – and even if you filter the sand, the sunlight that hits your water tank promotes the growth of microorganisms – typically bacteria your eyes cannot see – that still contaminate the water.

Furthermore, if like many Nigerians you don’t drink directly from your borehole/storage tank, the contaminated water can still make you sick because you brush your teeth with it, shower with it, and cook with it.

But what about harmful bacteria, parasites , and viruses, and the risk of infection?

“We’ve spent generations of science and effort to try and protect people from drinking raw water. It seems extraordinary that people want to go back to medieval times when millions of people died from infections that were carried by it,” says Val Curtis, Professor of Hygiene and Director of the Environmental Health Group at the London School of Hygiene and Tropical Medicine.

According to global health expert Curtis, the purpose of water is not nutrition – it’s hydration. “We need H20,” she says. “If we need any other minerals or magic compounds, we get them from our food. Water is not for nutrition, and the dangers of raw water outstrip any benefits by far.”