Chlorine Water Tablets: How to Use Them Safely at Home
The short answer: chlorine water tablets are a safe, cheap way to make clear water drinkable when you can’t boil, as long as you match the tablet to the exact amount of water printed on the pack, wait the full time the pack gives, and start with water that isn’t muddy.
Before you start
- The golden rule: read the pack. Tablets come in different strengths, each made for a set volume of water.
- Wait time: usually around 30 minutes, longer for cold or cloudy water, per the pack.
- Cloudy water: settle and strain it first, or the chlorine gets used up on the dirt.
- Good sign: a faint chlorine smell after the wait means it has worked.
- Never: swallow a tablet, give one to a child, or keep them where children can reach.
Prefer to listen? This post as a 2 min video · Watch the video
When the gas runs out, the power’s gone and floodwater has crept into the street, boiling every glass isn’t always possible. That’s exactly what chlorine water tablets are made for. Relief agencies hand them out after floods for good reason. But they only work when used the right way, and the most common mistake is simple: one tablet dropped into a random bucket. Here’s how to use them safely at home, what they can and can’t do, and how to keep them away from little hands. For more on monsoon water safety, see our Barsaat and Flood Season hub.
How chlorine tablets make water safe
Think of chlorine as a cleaner that goes hunting: it dissolves, spreads through every corner of the water and breaks open the germs that cause cholera, typhoid and most diarrhoea, and given enough time, it gets them. Time matters.
Two things slow it down. Dirt is the first, because mud and leaves soak up the chlorine before it ever reaches the germs, a bit like soap going grey and useless in a very dirty bucket. Cold is the second. Chemical reactions slow in cold water, which is why the pack may tell you to wait longer.
Most household tablets use a chemical called NaDCC (sodium dichloroisocyanurate) and others use different chlorine compounds, but you don’t need to know the chemistry. You need the volume.
How to use chlorine water tablets, step by step
- Read the pack first. Find the volume each tablet is made for. Some are for a 1-litre bottle, some for a 20-litre can, some for much more. Never guess.
- Measure your container. If you don’t know its size, fill it using a 1-litre bottle and count. Mark the level with a marker so you never have to count again.
- Clear the water first if it’s cloudy. Let it stand covered for an hour or two, then pour the clearer top part through a clean folded cotton cloth into your treating container.
- Add the tablet for that exact volume, using dry hands or the tablet’s own foil, and close the lid.
- Shake or stir with a clean spoon until it dissolves.
- Wait the full time on the pack. Put a phone timer on. If the pack gives a longer time for cloudy water, use it.
- Sniff. A faint swimming-pool smell after the wait means some chlorine is still there, which is what you want. No smell at all? The chlorine may have been used up; follow the pack’s advice.
- Store it covered and pour, don’t dip. Use the water within the time the pack gives, and wash hands before handling it; our monsoon hygiene routine covers the rest.
Taste trick
If the chlorine taste bothers you, leave the treated water in a clean covered jug for a few hours, or pour it between two clean jugs a few times. The smell fades. Adding a squeeze of lemon to a glass just before drinking also masks it, but only after the full waiting time.
Too much, too little: getting the amount right
Too little chlorine leaves germs alive, while too much makes the water taste so harsh that people quietly stop drinking it and switch back to the tap, which is its own danger in the heat. That’s why matching tablet to volume matters more than anything else in this article.
- Don’t break tablets into pieces unless the pack says you can.
- Don’t “add one more to be safe”. More isn’t safer. It’s just nastier to drink.
- If a pack is made for a bigger volume than your bottle, treat the bigger volume in a clean bucket and then fill your bottle from it.
Keeping tablets safe at home
Water tablets are small, often round and white, and in a foil strip they look a lot like medicine or sweets to a curious three-year-old who has watched adults pop things into their mouths all day. That’s the hazard.
- Store them high up, in their original pack, in a cool dry place, well away from medicines so nobody mixes them up.
- Never put tablets in a child’s water bottle yourself and hand it over before the waiting time is up.
- Don’t mix them with other cleaning chemicals, and don’t use pool chlorine or cleaning bleach in their place unless a health authority gives you a written method for that product.
- Check the expiry date. Old or damp tablets lose strength.
Chlorine tablets vs boiling vs phitkari
| Method | Kills germs? | Clears mud? | Best for |
|---|---|---|---|
| Boiling | Yes, reliably | No | Homes with fuel and time |
| Chlorine tablets | Yes, most germs, in clear water | No | No gas, travel, floods |
| Phitkari (alum) | Not reliably | Yes | A settling step before boiling or chlorine |
Alum and chlorine can work as a team: alum settles the mud, then you pour off the clear water and treat it. We explain why alum alone isn’t enough in Phitkari (alum) and water. Chlorine also has one real gap. A tough parasite called Cryptosporidium shrugs it off, which is one reason boiling stays the first choice when you can do it.
Myth: chlorinated water causes cancer or harms your stomach
The truth: the amounts from household tablets used as directed are the same low levels many city supplies use every day, and health agencies back this for drinking. The germs in untreated flood water are the far bigger, far faster danger.
Why people believe it: the strong smell makes it feel like a chemical is doing harm. Strong smell usually just means fresh water treatment, not an unsafe amount.
Someone swallows a tablet, especially a child: don’t make them vomit, rinse the mouth, give a few sips of water if they’re awake and can swallow, and call your local emergency number or poison line straight away (1122 in Pakistan, 112 in India), taking the pack with you. For anyone with a stomach illness, see a doctor the same day for blood in the stool, repeated vomiting, very little urine, sunken eyes or drowsiness; start packet ORS mixed exactly as the packet says. For baby formula, boiled and cooled water is still the standard advice. If anyone in the house has a kidney condition or is on dialysis, check with their doctor about the water they should use.
Chlorine tablet questions people ask
How long after adding a chlorine tablet can I drink the water?
Wait the full time printed on your pack, which is often about 30 minutes for clear water and longer for cold or cloudy water. Drinking early means some germs may still be alive.
How many chlorine tablets per litre of water?
It depends entirely on the brand and strength, so the pack is the only right answer. Each tablet is made for a set volume, so measure your container and match it exactly.
Are water purification tablets safe to drink every day?
Yes, when used exactly as the pack says. Many city supplies are chlorinated at similar low levels. If the taste puts you off drinking enough, try letting it stand covered for a while.
Can chlorine tablets clean muddy water?
Not properly. Mud uses up the chlorine and hides germs. Let the water settle, strain it through a clean cloth, then treat the clearer water.
Is chlorinated water safe for children?
Yes, treated water made up correctly is fine for children to drink. The tablets themselves must be kept out of reach. For infant formula, public-health advice is still boiled and cooled water.
Is chlorinated water safe in pregnancy?
Water treated as directed is considered safe to drink in pregnancy, and it’s far safer than untreated flood water. If you have concerns, ask your doctor or midwife at your next visit.
What if the water still smells strongly of chlorine?
A faint smell is a good sign. A very strong smell usually means more chlorine than needed for that volume. Let it stand covered to air out, and next time measure the volume more carefully.
Can I use bleach instead of chlorine tablets?
Only if a health authority gives you a method written for that exact product and strength, because household bleaches vary and many contain perfumes or additives. Scented or “thick” bleaches are never for drinking water.
Do chlorine tablets expire?
Yes. Check the date and keep them dry in their sealed pack. Tablets that are crumbly, damp or past the date may not be strong enough.
Do chlorine tablets remove chemicals from water?
No. They kill most germs but leave fuel, pesticides, arsenic and other chemicals untouched. Use sealed bottled water if you suspect chemical contamination.