To keep a water tank clean after cleaning, do four things: keep the lid and cover sealed, screen every opening, look inside once a month, and control what goes in when supply or a tanker arrives. Then clean again in 6 months. A cleaned tank does not stay clean by itself in Karachi, because the water that refills it carries silt, and heat does the rest.
This is the routine we give our own customers after a job. None of it needs tools beyond a torch.
Preparing for Post-Cleaning Maintenance
Before the cleaning team leaves
- Look inside both tanks yourself. Floor, walls and corners should be clean, with no standing dirty water. We ask every customer to do this before paying.
- Ask what they noticed. Cracks, a worn float valve, a damaged lid, rusted fittings. An empty tank shows things that a full one hides.
- Check that lids and covers are back in place and sitting properly.
- Write down the date. On the tank with a marker, on the fuse box, or in your phone with a reminder for six months ahead.
The first 48 hours
- Refill with the best water you can. If the line supply has just resumed after a long gap and is running cloudy, let the first flow pass before opening your inlet valve, if your connection allows it.
- Run each tap for a minute once the overhead tank has refilled. This clears old water and loosened sediment from the pipes.
- Clean the small parts. Unscrew tap aerators and shower heads, rinse out the grit, and refit. Replace or wash filter cartridges, which will be holding dirt from before the cleaning.
- Expect a faint chlorine smell in the first tankful. It is the disinfectant and it fades within a day or two. See how to disinfect a water tank after cleaning.
Fix what the cleaning revealed
If a crack, a leaking fitting or a broken lid was found, deal with it now, while you remember and before it lets dirt back in. See detecting and preventing leaks and common water tank problems.
Inspection and Cleaning Schedule
| How often | What to do |
|---|---|
| Every delivery | Look at tanker water in a clear glass before it goes in. Check the colour of line water when supply resumes after a gap. |
| Weekly | Glance at the overflow pipe and the roof around the tank for drips. Notice any change in the smell or colour of tap water. |
| Monthly | Open both tanks and look in with a torch. Check lids, mesh and the float valve. |
| After every storm | Check that the rooftop lid is still on and the underground cover has not let water in. |
| Every 6 months | Full cleaning and disinfection of both tanks. Every 4 months if you rely on tankers. |
| Yearly | Service the pump, replace float valve washers, check the tank stand or base, and review the condition of the lid and tank body. |
The reasoning behind the 6-month interval is in how often you should clean your water tank in Karachi, and the best months are in the best time to clean your water tank.
Steps to Maintain Your Water Tank
1. Keep it closed
An open or loose lid undoes a cleaning faster than anything else. Dust, leaves, insects, lizards and birds all get in. Rooftop lids should screw or clamp down. If yours just rests on top, tie it or weigh it, and replace it when it cracks. Underground covers should sit on a raised neck with a seal. See bird contamination in rooftop tanks.
2. Screen every opening
Fit fine stainless or plastic mesh over the vent and the end of the overflow pipe. These are open pipes leading straight into your water, and mosquitoes breed happily in a tank they can reach.
3. Keep light out
Algae needs light. An opaque tank with a closed lid stays free of it. If your tank is thin enough to glow in the sun, shade it, paint the outside, or plan to replace it. See preventing algae growth.
4. Keep it cool
Shade over a rooftop tank slows bacterial growth and helps chlorine last longer. Even a simple canopy helps.
5. Control what goes in
- Line water: the first water after a supply gap is the dirtiest. If you have an inlet valve and can see the flow, wait until it clears.
- Tanker water: ask the driver to run a little into a bucket first. Refuse a load that is visibly muddy or smells. Make sure the hose end has not been dragged through the gutter before it goes into your tank.
- Boring water: if you have sweet water as well, keep the two in separate tanks. Boring water leaves scale. See Karachi’s hard water problem.
6. Keep the water moving
Water that sits goes stale. If part of the house is unused, run those taps weekly. If you go away for more than two weeks, drain the overhead tank on your return and refill it before use.
7. Look after the float valve and pump
A float that sticks open floods the roof and wastes water. One that sticks shut leaves you dry. Lift it by hand once a month to check it shuts off cleanly. Keep the pump’s foot valve clear and have the motor serviced yearly. See pump system maintenance.
8. Keep the surroundings clean
No car washing over the underground cover, no rubbish or pet bowls beside it, and no standing water around it. On the roof, clear leaves and droppings from around the tank and do not store paint or chemicals next to it.
9. Never dip into the tank
Do not lower buckets, ropes or hands into the water. Draw water through the pump and taps only.
10. Treat drinking water separately
Even a well-kept tank holds Karachi supply water. Boil or filter what you drink. See filtration and cleaning in Karachi homes.
Regular Maintenance Checklist
Use this once a month. It takes about ten minutes.
- Underground cover intact, sealed and above floor level
- Area around the cover dry and clean
- Water in the underground tank clear, no smell, nothing floating
- Rooftop lid tight and uncracked
- Mesh in place on vent and overflow
- Walls of the overhead tank free of green or black growth
- No thick sediment visible on the tank floor
- Float valve shuts off fully
- No drips from fittings and no damp patches on the roof or ceiling below
- Overflow pipe dry
- Tap water clear in a glass, no smell
- Cleaning date still within 6 months
Signs that mean clean now, not later
- Coloured or cloudy water that does not clear
- A sewage or rotten-egg smell
- Worms, larvae or a dead animal in the tank
- Floodwater in the underground tank
- Stomach illness going round the household
More on these in signs your family may be drinking contaminated water.
Why Dirty Water Sometimes Returns Quickly
A cleaned tank stays only as clean as the water that goes into it. Karachi gets roughly half the water it needs (Geo News), supply is intermittent, and line water after a gap, tanker water and boring water can all bring fresh silt and colour into a tank within days. That comes from the incoming water, not from the cleaning. Our service guarantee explains what we redo free of charge and what is outside any cleaner’s control.
Maintenance cannot stop dirty supply, but it limits the damage: a sealed, shaded tank with a working float and a clean floor copes with a bad delivery far better than a neglected one.
Benefits of Effective Water Tank Maintenance
- The cleaning lasts. A maintained tank reaches its 6-month date with a thin layer of silt, not a bed of sludge.
- Safer water between cleanings. Sealed and screened tanks keep out the things that carry disease. See waterborne diseases common in Karachi.
- Problems are caught early. A monthly look finds a cracked lid or a weeping fitting before it becomes a contaminated tank or a wet ceiling.
- Less wasted water. A working float valve and tight fittings save water every day.
- Longer life for the pump and the tank.
The full case is in the benefits of regular water tank cleaning.
Frequently Asked Questions
How long does a tank stay clean after cleaning?
With sealed lids and reasonable supply water, it stays in good condition for about six months. With muddy tanker water or an open lid, much less.
Should I add chlorine to my tank between cleanings?
If you do, measure it. The level for drinking water at the tap is 0.2 to 0.5 mg/L under Pakistan’s national standard (S.R.O. 1063(I)/2010), which is far lower than the dose used during cleaning. Use test strips, and never add chlorine to a dirty tank and assume it has made the water safe.
How do I stop mosquitoes breeding in my tank?
Close the lid and fit mesh over the vent and overflow. They cannot breed in water they cannot reach.
Can I clean the tank less often if I maintain it well?
Good maintenance keeps you at 6 months instead of needing emergency cleanings. It does not replace the cleaning, because silt and biofilm still build up.
Due for Your Next Cleaning?
If the date on your tank is more than 6 months old, call or WhatsApp 0313-2796778. We work across Karachi, including Bahadurabad, Gulberg and Shah Faisal Town. The steps are on our service procedure page and the rates on the charges page.
About the author: Ahmar Shoaib is the founder of Karachi Tank Cleaning. He holds a BS in Chemical Engineering from Karachi University and has run the company’s cleaning and disinfection work since 2007. This article follows our editorial policy.
Sources: PCRWR figures on Karachi’s water demand and supply, reported by Geo News (May 2025); National Standards for Drinking Water Quality, S.R.O. 1063(I)/2010.
