Our water tank cleaning services in Karachi cover overhead rooftop tanks and underground sumps: we drain the tank, lift the sludge, scrub every wall, disinfect with food-grade chlorine at 200 ppm for 30 minutes, rinse, refill and issue a service certificate. A 500-gallon rooftop tank costs PKR 2,500–4,500 and a 1,500-gallon underground sump PKR 10,000–13,000.
Every tap in Karachi runs off a storage tank, not directly off the main. KWSB supply is intermittent, a few hours of pressure every second or third day, so households live off whatever sits in the underground sump and rooftop tank between fills. Sediment settles, biofilm grows on the walls, chlorine residual collapses within 48 hours of a refill, and by the time a metallic taste or green tinge shows up the bacterial load has been climbing for weeks. I am Saad Danish, founder of Nest Fumigation Services, and our team has been cleaning tanks across Karachi since 2024. This page covers prices, overhead versus underground work, our process, the chlorine chemistry, cleaning frequency and the areas we serve.
Water tank cleaning services in Karachi: prices by tank size
We publish our prices. These are the bands we quote for residential and small-commercial tanks; the final figure depends on measured capacity and access.
| Tank | Price (PKR) | Notes |
|---|---|---|
| Overhead rooftop tank, 500 gallons | 2,500–4,500 | Most common domestic job; smaller rooftop tanks start from PKR 2,500 |
| Overhead tank, 1,000 gallons | 4,500–8,500 | Large bungalow rooftop tanks |
| Underground sump, 500 gallons | 7,000 | Entry price for a small residential sump, including confined-space preparation |
| Underground sump, 1,500 gallons | 10,000–13,000 | Standard bungalow sump |
| Combined sump + rooftop (bungalow package) | 10,000–14,000 | Both tanks in one visit, 3–4 hours on site |
| Commercial tanks, 2,000–5,000 gallons | 14,000–22,000 | Clinics, restaurants, schools, offices |
| Multi-tank apartment roofs | Quoted per building | Priced after a survey of the roof and manifold |
Prices assume reasonable access: a working ladder, an openable lid and a power point within 30 metres. Tanks that need lid cutting or scaffolding are quoted on site. Rates are the same across Karachi, with one exception: residential jobs in Bahria Town Karachi carry a flat PKR 800 fuel surcharge per visit, waived on contracts of three or more visits. For factories, housing societies, food plants, hospitals and sites with several large tanks, see our commercial & industrial water tank cleaning programme.
Overhead vs underground tank cleaning
Most Karachi properties run a two-stage system: an underground sump receiving KWSB or tanker water at street level, and an overhead tank that a booster pump fills from the sump. The two fail in different ways, so we clean them with different protocols.
| Overhead rooftop tank | Underground sump | |
|---|---|---|
| Main problem | Algae on the sunlit wall, dust and droppings past warped lids, scale on the float valve | Heavy sludge from tanker water, darker and cooler, so more bacterial load |
| Access | Roof ladder rigging; stair-tower tanks surveyed first | Confined space: gas check and 15–20 minutes of forced ventilation before entry |
| Extra steps | Lid-collar and seam check, float-valve descale, overflow screen check | Longer pump-out, manual sludge lift, DPD chlorine test before refill |
| Price (PKR) | 2,500–4,500 (500 gal) · 4,500–8,500 (1,000 gal) | 7,000 (500 gal) · 10,000–13,000 (1,500 gal) |
Underground tank cleaning
Underground tanks are the harder half of the job. A below-grade concrete tank is a confined space: before anyone enters, we run a pre-entry gas check and force-ventilate for 15 to 20 minutes, because sealed concrete chambers accumulate CO2 and lose oxygen. The sediment load is different too, suction-pumped sludge rather than the light silt film an elevated tank collects, so the pump-out stage runs longer and the chlorine is verified with a DPD test before the tank is refilled. If your sump is tanker-fed, expect more sediment, not less. The full sump protocol, with confined-space detail, is on our underground tank cleaning page.
Overhead tank cleaning
Overhead and rooftop tanks fail differently. Plastic walls heat to 35–40°C in summer, chlorine breaks down faster, and blue-green algae (Microcystis aeruginosa) and filamentous green algae colonise the sunlit wall of tanks not cleaned in over a year. Lids warp or go missing and let in dust and bird droppings, and the float valve sticks with scale long before the tank itself looks dirty. Our overhead protocol adds a lid-collar and seam inspection, a float-valve descale and a check of the overflow screen, the entry point most contamination actually uses. Where a tank sits above a stair tower, we quote the access work in the survey rather than discovering it on the day.
In PECHS the rooftop tank picks up a failure the rest of the city mostly avoids: fine dust off Tariq Road, settling past lids and overflow pipes that no longer seal. That is why we run water tank cleaning in PECHS as its own protocol, with lid and overflow sealing done alongside the sodium hypochlorite sanitise.
A tank that keeps losing water, or shows damp patches on the wall beside it, usually has a crack or a failed joint, and cleaning will not seal it. We will tell you that on the survey rather than clean a tank that will leak again. For that we offer water tank waterproofing: we repair the cracks and joints and line the tank with a coating approved for drinking-water contact.
Tank types in Karachi homes and businesses
Older bungalows in PECHS, Garden and Bahadurabad pair a concrete sump with a galvanised steel rooftop tank. Newer houses and apartments in DHA Phase 6–8 and Bahria Town run PVC or fibreglass up top and polyethylene downstairs. Commercial buildings run 2,000–10,000 gallon sumps and rooftop manifolds.
Domestic vs commercial sizing
Domestic tanks run from 200 gallons (small flat) to 1,000 gallons (large bungalow). Commercial starts at 2,000 gallons for a clinic or restaurant and runs past 10,000 for towers, schools and hospitals. The process is the same in principle; access, time and the amount of chlorine solution differ.
How much sludge to expect
Tanker water carries suspended solids, Sindh dust, microsand and rust, and gravity drops all of it to the floor of the sump. Over six months we typically lift two to four inches of grey-brown sludge from a 500-gallon residential sump. We photograph it before it goes: it is the honest measure of how overdue the cleaning was.
Why Karachi water tanks need cleaning every 6 months
The common international guidance, clean once a year, was written for cities with continuous chlorinated municipal supply, where the tank is a backup rather than the primary water source. Karachi is not that city.
KWSB intermittence and tanker variability
On a 48-hour supply cycle every tank fills, partially drains and refills repeatedly. The chlorine residual in the supply drops to undetectable within 36–48 hours, especially in warm rooftop tanks, and once it is gone the tank is an unprotected reservoir. Tanker water is less predictable still: you rarely know where the load came from or whether it was ever chlorinated.
Sediment drives biofilm
The layer at the bottom of a sump is a substrate for biofilm: bacteria, extracellular polymers and trapped organic matter in a structured matrix. Pseudomonas aeruginosa attaches to sediment and to the wall, and once biofilm establishes, flushing with chlorinated water will not remove it, because chlorine in the bulk water cannot reach into the polymer matrix on the wall. Mechanical scrubbing is non-negotiable.
Coastal salinity in DHA and Clifton
Properties in DHA Phase 7–8, Clifton and the coastal strip deal with harder, more mineral-laden water. It leaves calcium and magnesium scale at the waterline, which biofilm can colonise. We see more scale in DHA Phase 8 than in Gulshan-e-Iqbal or North Nazimabad and factor that into the descaling step.
Seasonal triggers
Monsoon (July–September) drives extra demand: supply turbidity spikes in heavy rain, and warm, humid rooftop conditions accelerate algal growth. Add a September clean for any property not serviced since April.
Our 5-stage water tank cleaning process
This sequence runs on every job. Skipping the desludge or cutting the contact time produces a tank that looks clean but is not microbiologically clean.
Stage 1: Drain and desludge
We drain the tank to the lowest practical level using the existing outlet plus a submersible pump for the residual. Sludge is lifted manually from sumps and with a wet vacuum from rooftop tanks, and photographed before disposal.
Stage 2: Scrub and descale
Walls, floor, ceiling and the underside of the inlet pipework are scrubbed by hand with food-grade detergent, plus a dilute citric descaler where there is visible scale. For large commercial tanks one technician enters with confined-space ventilation. The rinse water is pumped out.
Stage 3: Chlorine disinfection
Every wall, the floor and the underside of the lid are wetted with a 200 ppm solution of food-grade sodium hypochlorite and held for a 30-minute contact time. Hard-to-reach corners and the inlet are treated by hand so no dead spot escapes exposure.
Stage 4: Rinse, refill and residual check
The disinfectant is drained and the tank rinsed with potable water. We refill and check free chlorine at the nearest tap, targeting about 0.2 ppm, enough to slow regrowth without being noticeable in taste.
Stage 5: Reseal and certify
We check the lid seal and overflow, then issue a one-page service certificate noting capacity, sludge volume, chemicals, contact time and the post-clean reading, with before-and-after photos on WhatsApp. This is a service record, not a lab-issued potability test: we are an applicator, not a testing lab. For a lab result we refer customers to PCSIR Karachi.
Microbiology of a neglected tank
A tank left for a year or more in Karachi conditions is a predictable mix of organisms, and the WHO target for drinking water is zero E. coli and zero total coliforms in any 100 ml sample.
E. coli and total coliforms
Escherichia coli indicates faecal contamination somewhere in the supply chain, usually at tanker level or through a damaged pipe segment. Total coliforms (Enterobacter, Klebsiella, Citrobacter) do not always mean faecal contamination, but they do mean the chlorine residual has failed.
Pseudomonas biofilm and algae
Pseudomonas aeruginosa reliably builds biofilm on tank walls. It is opportunistic, rarely a problem for healthy adults but a real one for infants, the immunocompromised and home-care patients. Biofilm is why a tank that is only flushed and refilled returns to its old counts within weeks: the wall keeps re-seeding the water. Microcystis aeruginosa can produce microcystin toxins at high cell densities, so a visible green tinge is not cosmetic.
Chemistry: chlorine dose and contact time
Why 200 ppm for 30 minutes
Disinfecting a cleaned tank is a surface job: the solution has to reach the wall where the biofilm was, at a strength and for a time that kills what scrubbing loosened. We use food-grade chlorine at 200 ppm with a 30-minute contact time on every surface, then rinse it out. The low 0.2 ppm figure applies only to the refilled water, never to the disinfection step.
Sodium hypochlorite mixing
We use commercial sodium hypochlorite with a known manufacture date, because it loses strength in storage. At 5% available chlorine (50,000 ppm), a 200 ppm working solution is 40 ml of hypochlorite per 10 litres of water. We measure with a graduated cylinder, not by eye.
Honest limits
We align to WHO drinking-water guideline values, but we do not hold NSF/ANSI 60 or 61 certification and we do not issue lab-equivalent potability certificates. For properties with vulnerable residents (infant formula, post-transplant recovery, home dialysis), pair our cleaning with periodic lab water testing.
How often should you clean a water tank?
Residential: every 6 months
Two cleans a year is the floor for any lived-in Karachi home. Typical scheduling is April, before summer heats the rooftop tank, and October, after monsoon turbidity. Households with infants, elderly residents or home dialysis should consider cleaning more often.
Commercial: every 3 months
Restaurants (Sindh Food Authority [1] inspections), clinics, schools and residential towers usually run quarterly. Higher turnover and a higher cost of failure push the cadence up; a tower on a shared manifold can have one contaminated tank affect dozens of units.
Triggering events
Clean straight away after a stomach-illness outbreak in the household, an unusual taste, odour or colour at the tap, a vacancy of 30 days or more, a tanker from an unfamiliar supplier, flood or sewage contamination, or any plumbing repair that left the tank open to outside air.
Areas we serve across Karachi
We clean tanks citywide from our DHA Phase 4 office. Several areas have their own page because the water and the building stock create a different problem there:
- Water tank cleaning in DHA: tanker sediment in Phase 6–8 sumps and hard-water scale near the coast.
- Water tank cleaning in Clifton: sea-air salt on rooftop tanks, block by block.
- Water tank cleaning in Gulshan-e-Iqbal: rust-fed sediment and shared apartment manifolds.
- Water tank cleaning in North Nazimabad: ageing galvanised tanks and low supply pressure.
- Water tank cleaning in Bahria Town Karachi: construction silt and filtration-plant supply (fuel surcharge as above).
We also cover PECHS, Bahadurabad, Gulistan-e-Jauhar, North Karachi and the rest of the city at the same rates.
What to expect on the day
A residential clean disrupts supply for two to four hours. We confirm location, capacity, last-clean date and access on the booking call. The team arrives with ladder, pumps, brushes, chemicals, PPE and a chlorine test kit, and the supervisor opens the lid with you, shows you the sediment and photographs the inside before work starts.
If water is essential during the work (medical needs, infant care), we can stage the job: rooftop tank first while the sump stays online, then switch. Ask for it when booking; it adds about an hour.
After cleaning, the tank is refilled and the residual tested at the tap. Do not switch on the geyser for 30 minutes after the refill, and run every tap for two minutes the next morning. Customers often book tank cleaning alongside floor cleaning or kitchen deep cleaning; see the cleaning services hub for the full list.
Book water tank cleaning in Karachi
WhatsApp: 0311-1101810. Send a photo of the tank lid or rooftop layout and the approximate capacity, and we will quote from our published bands.
Phone: 0311-1101810. Voice works best for multi-tank, commercial and annual-contract discussions.
Email: contact@nestfumigationservices.com. Preferred for commercial bookings and quotations on letterhead. Or use the contact page.
Office and hours. Plot #14, 2/1 2nd Gizri Street, DHA Phase 4, Karachi 75500. Mon–Sat 9:30 AM–8:00 PM, closed Sunday.
Frequently Asked Questions
How much does water tank cleaning cost in Karachi?+
A 500-gallon overhead tank costs PKR 2,500–4,500 and a 1,000-gallon overhead tank PKR 4,500–8,500. Underground sumps start at PKR 7,000 for 500 gallons and run PKR 10,000–13,000 for 1,500 gallons. A combined sump and rooftop bungalow package is PKR 10,000–14,000, and commercial tanks of 2,000–5,000 gallons are PKR 14,000–22,000.
How often should I get my water tank cleaned?+
Every 6 months for a Karachi home. Intermittent KWSB supply means the chlorine residual in a stored tank drops to undetectable within about 48 hours, so sediment and biofilm build quickly. Restaurants, clinics, schools and towers usually clean every 3 months. Clean immediately after a stomach-illness outbreak, a doubtful tanker load, a plumbing repair or a 30-day vacancy.
Is the chlorine safe for drinking water?+
Yes, used this way. We disinfect the empty tank’s surfaces with food-grade sodium hypochlorite at 200 ppm for 30 minutes, then drain and rinse before refilling. The refilled water carries only a low residual of about 0.2 ppm. Keep the geyser off for 30 minutes after the refill and run each tap for two minutes the next morning.
Can you clean the overhead tank and underground sump in one visit?+
Yes. Most bungalow jobs are a combined package: PKR 10,000–14,000 for both tanks, about 3–4 hours on site. The sump needs confined-space preparation (a gas check and 15–20 minutes of forced ventilation) and a longer pump-out; the rooftop tank is quicker. We can stage the work so one tank stays online.
Do you add mosquito larvicide to drinking-water tanks?+
For drinking-water storage tanks we use an insect growth regulator briquet (methoprene or pyriproxyfen) or temephos, which are approved for drinking water and last. Bti is also safe for drinking water but only lasts days, so we keep it for open, frequently refreshed water. A sealed lid and screened overflow matter more. For roof-wide breeding, see mosquito control.
How do you handle apartment buildings with several tanks?+
Towers run several tanks on a shared manifold, so one contaminated tank can affect dozens of flats. We clean riser by riser to keep partial supply online, and log every tank’s capacity, sludge volume, contact time and post-clean reading on one consolidated certificate. Multi-tank roofs are quoted per building after a survey; large sites are covered by our commercial programme.