Water safety in Karachi is hard to judge by eye. The most dangerous contamination has no colour, smell or taste, and the signs people do notice often appear only after a problem has been building for months. Still, there are patterns worth knowing, both in the water and in the household’s health.
Below are ten warning signs, what each usually points to, and what to do about it. None of them is a diagnosis. Illness needs a doctor, and only a laboratory can confirm what is in the water.
In brief
- Clear water is not proof of safe water. The germs that matter are invisible.
- Repeated stomach illness in one household, or in several flats of one building, is the strongest warning.
- Colour, smell and grit each point to a different cause, set out in the table below.
- You can check your own tank in five minutes from the outside. Never climb into an underground tank.
- If the last cleaning was more than six months ago, or nobody knows, the tank is overdue.
Why Karachi households need to pay attention
Karachi gets a little over half the water it needs, and it arrives for a few hours at a time through an ageing network. Every home stores it, usually in an underground tank and again on the roof. Testing has found most samples unsafe: in the 2017 round carried out for the Supreme Court’s commission, 107 of 118 Karachi samples failed. How the water gets that way is covered in our guide to KWSB water supply. The tank is where everything it carries comes to rest.
Ten warning signs
1. Stomach upsets that keep coming back
One bad meal explains one illness. Repeated cramps, nausea or loose motions in the same household, with no obvious food link, point to something everyone shares, and water is the most common shared exposure.
2. Several people ill in the same week
When two or more family members fall ill together, look for a common source. In a block of flats, ask the neighbours. If other households are affected, the shared tank is a prime suspect.
3. A diagnosis of typhoid or hepatitis A or E
These spread by the faecal-oral route, often through water. A confirmed case in the house is a reason to boil all drinking water and clean both tanks immediately. Our article on typhoid, E. coli and the water tank link explains the route.
4. Cloudy or coloured water
Brown or yellow usually means rust and silt, often after a line repair or a long gap in supply. Green suggests algae, which needs light, so check the lid. Milky water that clears from the bottom up is usually just air.
5. A smell
Earthy or musty smells point to algae and organic growth. A rotten-egg smell means decay without oxygen, typically in deep sludge. A sewage smell is an emergency: stop drinking the water and have the underground tank inspected for seepage.
6. An odd taste
Metallic tastes come from rust and old pipes, salty or bitter tastes from borehole or tanker water, and a strong chlorine taste from recent dosing. Any sudden change is worth investigating.
7. Rashes or sore eyes after bathing
Skin and eye irritation that appears after showers and eases when you are away from home can be caused by bacterial growth in stored water, though hard water and soaps are also common culprits.
8. Slime, sediment or insects in the tank
Run a finger along the inside wall near the waterline. A slippery film is biofilm. A dark layer on the floor is sludge. Wriggling larvae mean mosquitoes are breeding, and the WHO’s advice for dengue control is to keep water storage containers covered and cleaned.
9. Filters clogging quickly
If cartridges that should last months turn brown in weeks, the tank is feeding them sediment. This is covered in water filter versus tank cleaning.
10. Nobody remembers the last cleaning
The Sindh health department’s minimum is once a year before summer. If it has been longer than six months, or the date is unknown, treat the tank as overdue.
Read the signs: a quick reference
| What you notice | Most likely cause | First step |
|---|---|---|
| Brown water after supply returns | Sediment stirred up in the mains | Let it run to waste; clean the tank if it persists |
| Green tint or musty smell | Algae from light entering the tank | Fix or replace the lid; clean |
| Rotten-egg smell | Deep sludge | Clean with sludge removal, not just rinsing |
| Sewage smell | Seepage into the underground tank | Stop using for drinking; urgent inspection |
| Grit in buckets and filters | Sludge reaching the outlet level | Clean; check outlet height |
| Larvae or insects | Open or damaged lid, missing mesh | Seal, screen and clean |
| Recurring illness, clear water | Microbial contamination you cannot see | See a doctor; boil water; clean and disinfect |
A five-minute tank check
- Look at the lids. Do both close fully? Any cracks, gaps or missing covers?
- Shine a torch inside from the opening. Can you see the floor? Is there a dark layer or floating matter?
- Smell the air at the opening. It should smell of nothing.
- Feel the wall of the rooftop tank near the waterline for slime.
- Fill a clear glass from a bathroom tap first thing in the morning and hold it to the light.
Do not climb into an underground tank to check it. Closed tanks can hold gases that overcome a person in seconds. In June 2025, five men died in an underground water tank in Ibrahim Hyderi, three of them while trying to rescue the first two.
What a neglected tank contains
- Sludge: silt, rust and organic matter that settle with every fill
- Biofilm: bacteria attached to the walls in a protective layer
- Algae: where light enters
- Scale: mineral crust, heavier with borehole water
- Whatever the supply delivered: the tank stores it until someone removes it
Warm weather speeds all of this up, as described in how Karachi’s heat affects tank water, and the weeks after heavy rain are the highest-risk period, covered in our monsoon guide.
What to do if you spot these signs
- Protect drinking water today. Boil it or use a filter you trust.
- See a doctor for anyone who is ill, especially children, pregnant women and the elderly. There is more for parents in our children’s water safety guide.
- Check the lids and the tank using the five steps above.
- Have both tanks cleaned and disinfected. What a proper job involves is on our cleaning procedure page, and this walk-through of a professional cleaning shows what to expect on the day.
- Set a schedule so it does not get to this point again. See how often to clean a water tank in Karachi.
- Consider a lab test if illness continues after cleaning, to check the supply itself.
To arrange a cleaning, contact the branch for your area: Gulshan, Jauhar and East Karachi or DHA, Clifton and South Karachi. The online calculator gives a fixed price for standard homes.
After a cleaning: what should change
If the tank was the cause, improvements follow a rough order. Smell and colour usually clear within a day or two of refilling. Filter cartridges last noticeably longer over the following weeks. Recurrent stomach upsets should become less frequent over the next month or two, though they rarely stop overnight because food and hands are also sources.
If nothing changes, the supply itself is the likely problem. At that point a laboratory test of the incoming water, a check of the underground tank for seepage, and stricter treatment of drinking water are the next steps. Water safety in Karachi is a matter of several barriers working together, and the tank is only one of them.
Signs by water source
What you notice depends partly on where the water came from.
| Source | Typical signs | What they suggest |
|---|---|---|
| Piped supply | Brown first flow after outages; fine silt | Sediment and contamination picked up in the mains |
| Tanker | Sand in buckets; quality that changes with each load; sometimes a salty taste | Unknown source; tanker itself rarely cleaned |
| Borehole | Salty or bitter taste; white crust on taps; soap that will not lather | Hard, saline groundwater; scale building up in the tank |
| A mix | All of the above, varying week to week | Faster build-up of both sludge and scale |
Frequently asked questions
My water looks clear. Does that mean it is safe?
No. The bacteria and viruses that cause typhoid, cholera and hepatitis are invisible at the levels that cause illness. Clear water is a good sign for sediment, not for germs.
Can I test my water at home?
Home kits give a rough indication at best. For a reliable result, use an accredited laboratory and follow its sampling instructions exactly.
The water is only dirty for a few minutes after supply comes. Is that a problem?
That first flush is sediment from the mains. It settles in your underground tank each time, which is how sludge builds up. Let it run to waste where you can, and keep to a cleaning schedule.
Will cleaning the tank stop the illness?
It removes one likely source. If the supply itself is contaminated you still need to boil or filter drinking water, and continuing illness should be discussed with a doctor.
Is a chlorine smell a bad sign?
A faint chlorine smell means disinfectant is present, which is good. A strong one after someone has dosed the tank fades in a day or two. No chlorine smell at all is the usual state of stored water in Karachi.
Only one bathroom has smelly water. Is that the tank?
Probably not. A problem at a single outlet usually lies in that tap, its pipe or the drain beneath it. Tank problems show at every tap fed from it.
Sources
Figures in this article were checked in October 2026 against the following:
- Dialogue Earth, 28 July 2017: 91% of Karachi’s water unfit to drink (PCRWR results)
- WHO: Dengue fact sheet
- Geo News, 13 September 2025: Naegleria claims another life in Karachi, toll hits five in Sindh
- Dawn, 11 June 2025: Five dead after inhaling toxic gases in water tank in Karachi
- WHO: Drinking-water fact sheet
About Khan Tank Cleaning
Khan Tank Cleaning has cleaned residential, commercial and industrial water tanks in Karachi since 2005. The company was founded by Mateen Khan, who still oversees quality control at both branches. More about us, or get in touch: 0333 0293174 for DHA and South Karachi, 0340 2717530 for Gulshan and East Karachi, both answered 24 hours.
Mateen Khan is the Founder & Owner of Khan Tank Cleaning, Karachi’s first dedicated professional water tank cleaning company (est. 2005). With 20+ years of industry experience, he leads an ISO 9001 & ISO 45001 certified team that follows a strict 8-step process using industrial equipment and food-grade disinfectants. Mateen is committed to making clean, safe water accessible to every household and business in Karachi.