Tap, boiled, filtered or bottled: which drinking water is safe at home in Lahore?

Ask ten families in Lahore how they make their drinking water safe and you will hear four answers: we drink it from the tap, we boil it, we have a filter, or we buy bottles. Each one protects you from some things and not from others. This guide sets out what each method actually does, where it falls short, and the simple habits that make any of them safer.

Why the water in your glass is not the water in the main

Water can leave a tube well or a treatment point in good condition and still arrive at your glass carrying germs. On the way it travels through old pipes that sometimes run close to drains, it can be pulled into a leaking line when the supply drops, and in most houses it then sits in an underground or rooftop tank before it reaches the tap.

That last step matters more than people think. A tank that has not been cleaned in a year collects silt, rust and slime on its walls, and an open or cracked lid lets in dust, insects and birds. Before deciding how to treat your water, it is worth knowing that the tank on your roof is part of your water supply.

Straight from the tap

Tap water is the cheapest and the most convenient, and it is fine for washing, cleaning and bathing. For drinking, the risk is that you cannot see what it picked up on the way. Diarrhoea, typhoid and hepatitis A and E are all spread through water contaminated with sewage, and they are common enough in Pakistan that drinking untreated tap water is a gamble, especially for children and older family members.

• If the water is cloudy, smells of sewage or chlorine strongly, or changes colour, do not drink it untreated.
• Water from the tap after the supply has been off for hours is the most likely to have picked something up. Let it run first.
• If you have no other option, boil it.

Boiled water

Boiling is the oldest method and it works for what it is meant to do: bringing water to a full, rolling boil kills the bacteria, viruses and parasites that cause most waterborne illness. The World Health Organization's guidance is a rolling boil for about a minute.

What boiling does not do is remove what is dissolved in the water. Salts, heavy metals such as arsenic, and other chemicals stay behind, and as some of the water boils off they become slightly more concentrated. Boiling also does nothing about taste or cloudiness.

Where boiled water goes wrong

• It is cooled in an open pot and picks up dust and germs again.
• It is poured into a bottle or cooler that was never washed.
• Someone in a hurry tops it up with tap water.
• Gas is short and the water is only heated, not brought to a full boil.

If you boil, cool the water in the same covered pot, pour it into a clean covered container with a tap or a narrow neck, and use it within a day or two.

Home filters and RO systems

Many Lahore homes now have a reverse osmosis (RO) filter under the kitchen sink. A good RO system pushes water through several stages: a sediment filter for dirt and rust, a carbon filter for chlorine and taste, and a membrane that removes most dissolved salts and many chemicals. Done properly, it takes out much more than boiling does.

The catch is maintenance. Filters that are not changed clog up, and a wet, old cartridge can grow bacteria inside it, so a neglected filter can hand you water that is worse than what went in. RO also wastes a share of the water it treats, and it removes useful minerals along with the harmful ones.

• Change the sediment and carbon filters as often as the maker says, usually every few months in Lahore.
• Have the membrane checked or replaced on the schedule in the manual.
• Write the date of each change on a piece of tape on the cabinet door, so nobody has to remember.
• If the taste changes or the flow drops, get it serviced before you keep drinking from it.

Sealed bottled water

Bottled water from a certified supplier is treated and tested before it is sealed, so you are not relying on your pipes, your tank or your filter. That is the reason most offices and many homes in the city use 19 litre bottles for drinking and cooking.

Bottled water is only as good as the company behind it, though. Check that the supplier is certified and that you can look the certificate up yourself, that every bottle arrives with an unbroken seal, and that the bottles look clean and are not scratched cloudy. Our guide to what our certifications mean shows how to check them.

No method is safe if the water is stored badly afterwards. A clean container with a lid matters as much as how the water was treated.

Habits that make any water safer

• Clean the rooftop or underground tank at least twice a year, and keep its lid closed and sealed.
• Keep drinking water covered, and pour or tap it out rather than dipping a glass in.
• Use the same safe water for drinking, cooking, making tea, washing fruit you eat raw and making baby feeds.
• Wash your hands before handling drinking water, bottles or the dispenser.
• Clean your water dispenser or cooler regularly; our guide to home dispensers covers how.

Which one should you choose?

There is no single answer for every home. Boiling is cheap and reliable against germs if it is done fully and stored properly. A well-maintained RO filter removes more, but only while somebody keeps up with it. Sealed bottled water from a certified supplier takes the guesswork out of your pipes and tank, at a monthly cost. Many families mix them: bottled water for drinking and cooking, tap water for everything else.

If anyone in the family has repeated stomach upsets, or you have reason to think your area's water has a chemical problem, have the water tested by a laboratory and speak to a doctor. A test tells you what is actually in your water, which no guide can.

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