Water Tank Cleaning Lebanon: What Lebanese Studies Found, How Often, and the WHO Method

In Lebanon, intermittent supply forces households to store water for days, and Lebanese studies found that bacterial counts in tanks rise with storage time and temperature, especially in summer. Proper cleaning follows WHO Technical Note No. 3: inspection, physical cleaning and sediment removal, disinfection with a measured chlorine solution, and checking residual chlorine before use. There is no binding Lebanese schedule; as a regional reference, Kahramaa recommends inspecting every two months and cleaning at least every six to ten months.

Why every home in Lebanon has a water tank

In most countries, water arrives from the network when you open the tap. In Lebanon, public supply is intermittent: water reaches many neighbourhoods on a schedule of hours or days, not continuously. Research from the American University of Beirut on the impact of intermittent water supply on water quality in Lebanon describes exactly this: intermittent supply forces households to store water, and storage itself changes the quality of that water. That is why almost every building has roof tanks, many have underground tanks too, and the tank, not the network, is what your family actually drinks from, cooks with and washes in.

A tank is not a passive container. It is a warm, dark, still body of water, often topped up from several different sources, and left for days at a time. Those are the conditions in which bacteria grow. Keeping it clean is a health decision, not a housekeeping detail.

What Lebanese studies say about tank water

This guide is not based on general warnings. It is based on research carried out on tanks in Lebanon itself.

Storage raises bacterial counts

In a study by the Lebanese American University published in Water Science and Technology, 500-litre household tanks of two types, galvanised steel and black polyethylene, were tested. Average bacterial counts rose markedly after 7 days of storage in both types, and counts correlated with temperature, pH and storage time.

Summer is worse

Another LAU study concluded that bacterial growth in drinking water is a problem in Lebanon, most pronounced in household tanks during summer when temperatures are high, with large increases in counts after 4 and 7 days of storage. In household tanks in Byblos, bacterial counts ranged from 5 to 40,000 colony-forming units per millilitre across black polyethylene, fibreglass, asbestos-cement and galvanised steel tanks.

Sidon: acceptable chemistry, worrying bacteriology

A study from Beirut Arab University collected 50 samples from household tanks in Sidon. Most physical and chemical indicators were within World Health Organization limits, but bacteriological testing found bacteria including enteric bacteria, and the researchers concluded that the household water was unsuitable for drinking and domestic use. The lesson matters: water can look clear and pass a chemical test while remaining bacteriologically contaminated.

The answer is not pouring chlorine at random

The AUB research warned that adding disinfectant at random to deal with bacteria creates another problem: unwanted disinfection by-products. Disinfection must be measured, and part of a real tank clean, not a substitute for it.

Lebanon's water crisis: why the tank matters more than before

In July 2021, UNICEF warned that water supply systems in Lebanon were on the verge of collapse, with more than four million people at risk of losing access to safe water. By its figures, more than 71 percent of people fell into "extremely critical" and "critical" vulnerability levels, and around 1.7 million people were getting only 35 litres a day compared with a national average of 165 litres before 2020. UNICEF also noted that power cuts disrupt water treatment, pumping and distribution, and that prices for water from the private sector had risen.

In October 2022, the Ministry of Public Health notified the World Health Organization of laboratory-confirmed cholera cases in the North and Akkar, the first cholera outbreak in Lebanon since 1993. By 12 November 2022, Lebanon had recorded 3,485 cumulative cases according to the WHO Regional Office's weekly epidemiological bulletin. Cholera is transmitted mainly through contaminated water or food.

The practical conclusion for every household: when water comes from several sources, the network, private tankers and wells, and sits for days in the heat, a clean and sealed tank is the closest line of defence to your family.

The journey of water from source to your tap

Understanding the path explains where contamination enters:

Source: the public network, a private tanker, a well or a spring, each with its own quality.
Underground or ground tank: fills when supply arrives; collects sediment from every source.
Pump: lifts water to the roof; depends on electricity or a generator.
Roof tank: stores water in the sun and heat for days.
Pipes, heater and filters: deliver water to taps, and can hold their own build-up.

Every stage adds risk, and the tanks are where the water spends the longest time.

Electricity, pumps and tanks

Lebanon's power cuts affect water as much as light. When the pump cannot run, roof tanks empty and the household waits; when power returns, the pump sends whatever is in the ground tank upward, sediment included. Pumps that run dry or cycle on unstable power fail earlier. Keeping the ground tank clean, fitting a float switch that stops the pump when the tank is empty, and maintaining the pump itself are part of keeping the water system healthy. Power Zone's pump maintenance service covers this side.

For tenants: what to ask before moving in

Where are the tanks, and when were they last cleaned?
Which sources fill them: network, tanker, well?
Who is responsible for cleaning, the landlord, the tenant or the building committee?
Are the tanks covered and sealed?
Is there a filter at the kitchen tap, and who changes it?
Is there a record of cleaning dates?

A practical plan through the year

Before summer: full clean and disinfection of all tanks, inspection of covers and float valves, and pump check, so the hot months start with clean tanks.
During summer: monthly visual inspection; keep covers closed; avoid letting water sit for very long periods; clean again if sediment or smell appears.
After summer: second clean to remove what accumulated during the hottest months.
After any contamination event: clean immediately: an animal or insects in the tank, network works, a long interruption, or a visible change in colour or taste.
After a long absence: drain, inspect and clean before using the water.

Kitchens and restaurants in Lebanon

For food businesses, tank water touches everything: washing produce, ice, drinks, cleaning surfaces and equipment. A restaurant that stores water for days in summer without a cleaning programme is taking a risk with every customer. Food businesses should keep tanks on a written schedule, keep cleaning records available for inspection, use filtration where water is used in food and drinks, and treat any change in water quality as an urgent issue, not a cosmetic one.

Types of tanks in Lebanon and what each needs

Plastic (polyethylene) tanks

The most common roof tank today. Light, cheap and easy to install. Black and dark tanks limit algae growth by blocking light; translucent tanks in the sun grow algae quickly. Plastic degrades in years of sun and can crack; covers warp and stop sealing. Easy to clean because the surface is smooth.

Fibreglass tanks

Durable and resistant to corrosion, common in older buildings and larger installations. The inner surface can become rough with age, which lets biofilm cling; cleaning needs more scrubbing.

Old asbestos-cement (Eternit) tanks

Still found on older roofs. Porous surfaces hold sediment and biofilm, and cracked or crumbling tanks should be replaced rather than repaired. Handling and disposal of asbestos-cement needs care; do not break or grind the material.

Galvanised steel tanks

Strong, but prone to rust once the galvanising wears, which colours the water and provides surfaces for bacteria. Rust flakes in the bottom are a sign the tank is nearing the end of its life.

Underground concrete tanks

Large, cool and out of the sun, which helps, but they collect the most sediment because every source passes through them, and they are the hardest to inspect. Cracks can let groundwater or sewage seep in. They need periodic inspection by someone with the right equipment and safety training.

Signs your tank needs cleaning now

Sediment or sand in the bottom of glasses or in the washing machine filter.
Cloudy, coloured or smelly water, especially after the pump runs.
Green or black slime on the inside walls or on the float valve.
Insects, larvae or an animal found in the tank.
A cover that does not close or is missing.
Recent network works or a long interruption in supply.
Stomach illness in the household with no other explanation.
No record of when it was last cleaned.

How often should a tank be cleaned in Lebanon?

To be honest: we have not found a binding Lebanese schedule for cleaning household tanks. As a regional reference, Qatar's Kahramaa, in its publication on water quality in household tanks, recommends inspecting the tank at least every two months, cleaning and disinfecting it at least once every six to ten months, and chlorinating before use if residents have been away from the house for more than two weeks.

In Lebanese conditions, several factors push toward more frequent cleaning:

Heat: Lebanese studies link summer and high temperature to higher bacterial counts in tanks.
Long storage: the more days water sits in a tank, the more bacteria grow.
Multiple sources: a tank filled from the network, tankers and wells receives water of different qualities with different sediments.
Tank condition: loose covers and old tanks need closer attention.

In all cases, clean the tank immediately after any known contamination: an animal or insects inside, network maintenance, a long interruption, or an obvious change in colour or taste.

How proper cleaning and disinfection is done

WHO Technical Note No. 3 on cleaning and disinfecting water storage tanks and tankers describes a four-step method. This is the method to hold anyone cleaning your tank to:

Inspection and assessment: the tank is examined inside and out, including walls, cover, openings and connections, and its type and size recorded. A cracked or rusted tank may need repair or replacement before any cleaning.
Physical cleaning: the tank is emptied, sediment removed from the bottom, the inner walls scrubbed to remove slime and algae, then rinsed with clean water and the rinse water drained away.
Disinfection: the tank is disinfected with a chlorine solution at a measured concentration and left for sufficient contact time. The water used for disinfection contains a high concentration of chlorine and must be disposed of carefully.
Check after disinfection: residual chlorine is measured in the water before the tank returns to use, to confirm it is at a suitable level.

Physical cleaning is the foundation. Disinfecting over sediment and slime is far less effective, because bacteria shelter inside that layer.

Why entering a tank without equipment is not advised

Large underground and ground tanks are confined spaces. Oxygen can be low, gases can accumulate, surfaces are slippery, and chlorine fumes during disinfection are harmful. Every year people are injured or worse cleaning tanks on their own. Professional teams use ventilation, lighting, harnesses, a second person outside, and proper protective equipment. Roof tanks are usually cleaned from the opening without entering.

After cleaning: steps not to skip

Refill from the cleanest available source, not from a tanker of unknown quality.
Run taps briefly to flush the pipes after refilling.
Replace or clean tap filters, because disturbed sediment reaches them first.
Check that the cover is sealed and the overflow is screened.
Note the date of cleaning in your tank record.

Private tanker water: what you need to know

As public supply declines, many households depend on private tankers, and UNICEF has noted rising prices for private-sector water. The problem is that tanker water quality varies from one supplier to another and from one delivery to the next. To reduce the risk:

Ask the supplier where the water comes from.
Look at the cleanliness of the tanker and its hoses.
Do not fill a dirty tank with new water; the new water is contaminated by what is already in the tank.
If you notice sediment or an unusual colour after a particular delivery, clean the tank rather than waiting.
Remember that tanker water is usually for domestic use; do not assume it is safe to drink.

The WHO technical note states that tankers themselves must be cleaned and disinfected before being used to transport water, especially if previously used for other purposes.

What happens in a professional cleaning visit

Inspection of the tank, cover, float valve, overflow and connections.
Isolation of the tank and draining to a safe discharge point.
Removal of sediment and scrubbing of walls, floor and fittings.
Rinsing until the rinse water runs clear.
Disinfection with a measured chlorine solution and the required contact time.
Final rinse and check of residual chlorine.
Refilling, and a report with findings, photos and the next recommended date.

Questions to ask anyone cleaning your tank

Do you remove the sediment and scrub the walls, or only drain and refill?
What disinfectant and concentration do you use, and how long is the contact time?
Do you measure residual chlorine before handing the tank back?
How do you dispose of the disinfection water?
What safety equipment do you use for underground tanks?
Will I receive a written report with photos?

Returning to a closed home: summer apartments and expatriates' houses

Many Lebanese families own mountain or village homes used in summer, and many expatriates return to homes that stood empty for months. Water that sat in a tank all that time is the worst case: warm, still and old. Before using it, drain the tanks, inspect them, clean and disinfect, then refill. Kahramaa's regional guidance even recommends chlorinating before use after an absence of more than two weeks.

Mountain homes, wells and springs

Outside the cities, many homes draw from wells or springs. Groundwater can carry sediment, minerals and contamination from septic systems or agriculture, and spring quality changes with rainfall. Tanks fed from these sources need the same cleaning discipline, plus consideration of filtration and, where water is used for drinking, laboratory testing.

Laboratory testing: when it is worth it

Routine cleaning does not require testing, but testing is worth it when water is used for drinking, when there is illness in the household, when the source has changed, after a contamination event, or for food businesses and buildings with many residents. A microbiological test tells you what the eye cannot: the Sidon study found bacteriological problems in water that passed chemical tests.

When replacement is the answer

Replace a tank when it is cracked, leaking or rusted through, when an asbestos-cement tank is crumbling, when the inner surface is so rough that it cannot be cleaned, or when the cover cannot be sealed. A new tank in the right material and size, installed with a sealed cover, screened overflow and accessible opening, is easier to keep clean for years.

Residential buildings: shared tanks and the building committee

In apartment buildings, the main ground tank and often the roof tanks are shared. One neglected shared tank affects every apartment. The building committee should keep a cleaning schedule for shared tanks, keep records that any resident can see, decide who pays, and coordinate cleaning days so residents can store water in advance. For tenants and owners alike, asking the committee for the last cleaning date is a reasonable request.

Tanks and mosquitoes

An open or badly covered tank is a breeding site for mosquitoes, and larvae in the tank are a sign that the cover and overflow are not sealed. Fit a tight cover and mesh on the overflow and vent, and clean the tank if larvae are found.

Heat and sunlight

Roof tanks in direct sun warm quickly, and warm water favours bacterial growth. Dark tanks block light; shading or insulating tanks reduces heat gain; and keeping water moving by not oversizing storage reduces the time water spends warming. Lebanese studies make the summer effect clear.

Filters: the line of defence after the tank

Point-of-use filters at the kitchen tap, and whole-house filters after the tank, catch sediment and, depending on the type, reduce some contaminants. They are not a replacement for a clean tank: a filter fed by a dirty tank clogs quickly and can become a growth site itself. Change cartridges on schedule and after tank cleaning. See our water filtration installation and maintenance service.

Chlorine: measured use, not random use

Chlorine is the standard disinfectant for tanks, and WHO's method relies on it. But the AUB research warns against random dosing, which creates disinfection by-products. The right approach is a measured concentration for cleaning, adequate contact time, thorough rinsing, and checking residual chlorine before use. Pouring bleach into a full tank "to be safe" is neither safe nor effective.

Water heaters: the forgotten storage tank

A water heater is also a storage tank, usually fed from the roof tank, and it collects sediment and scale from every litre that passes through it. Warm, still water in a heater that is switched off for long periods, common in Lebanon when electricity is rationed, is another place where bacteria can grow. Drain and flush heaters periodically, check the safety valve, and keep them on the same maintenance record as the tanks.

Short-term rentals and guest apartments

Apartments rented to visitors and expatriates for short stays in Beirut and the mountains have a particular problem: they stand empty between guests, then are used intensively for a few days. Water sits in the tank through the gaps. Owners and managers of such apartments should schedule tank cleaning before the high season, flush the system before every arrival, provide filtered or bottled drinking water, and keep the cleaning record available, because a guest who falls ill will ask about the water first.

The cost of not cleaning

Tank cleaning is inexpensive compared with what it prevents: medical costs and lost days from waterborne illness, clogged and damaged pumps and valves from sediment, filters that need replacing far too often, stained laundry and fixtures, and the premature replacement of a tank that was allowed to corrode or crack. In food businesses, add the risk of inspection findings and reputational damage. Measured against those, a planned cleaning programme is one of the best-value maintenance items in a Lebanese building.

The same logic applies to timing. A clean scheduled in spring, before the heat, costs the same as one booked in August after the water has already turned, but it prevents the problem instead of reacting to it. Building the two cleanings into the annual calendar, alongside pump and filter checks, turns tank hygiene from an emergency into a routine.

Self-inspection guide for your tank

Open the cover in daylight with a torch.
Look at the water surface: floating debris, insects, film.
Look at the walls: slime, algae, rust.
Look at the bottom: sediment depth and colour.
Check the float valve and inlet for build-up.
Check the cover seal, vent screen and overflow screen.
Check around the tank for leaks and damp.
Note what you saw and the date.

Do not climb into underground tanks to inspect them; look from the opening or call a team with the right equipment.

Schools, restaurants and institutions

Schools and parent committees

Children are more vulnerable to waterborne illness. Schools should have a documented tank cleaning schedule, filtered drinking water points, and records available to parent committees who ask.

Offices and commercial buildings

Offices depend on tank water for pantries and washrooms. Building management should treat tank cleaning as part of the maintenance programme with records, not as an occasional request.

If you suspect the tank water is contaminated

Stop drinking it and avoid using it for food preparation; use bottled water for drinking in the meantime.
Do not add disinfectant at random.
Inspect the tank for an obvious cause.
Arrange a clean and disinfection, and consider a laboratory test.
If anyone in the household is ill, seek medical advice.

Design that makes cleaning easy: new buildings and renovation

When installing or replacing tanks: place them where they can be reached safely; fit a sealed, lockable cover and screened vent and overflow; provide a drain valve at the lowest point so sediment can be flushed; use dark, opaque materials for roof tanks; size storage to need rather than oversizing; and label tanks and valves. These choices cost little at installation and save years of difficulty.

Leaks around the tank and roof damp

Overflowing or leaking tanks are a common cause of roof damp, ceiling stains and damage to waterproofing in Lebanese buildings. A float valve that does not close, a cracked tank or a loose connection can run for weeks unnoticed. Inspect around tanks during each check, and fix leaks promptly; our leak detection and repair and waterproofing services cover the consequences.

Children and the elderly

Young children, older people and anyone with a weakened immune system are most at risk from contaminated water. Households with vulnerable members should be stricter about cleaning schedules, filtration and drinking water sources.

The limits of tank cleaning: what it does not fix

A clean tank cannot fix a contaminated source, corroded pipes, a dirty water heater or old filters. It is one step in a chain. If problems persist after cleaning, look at the source, the pipework and the fittings. Our water heater maintenance and plumbing services address the rest of the chain.

A simple tank record

Keep one line per event: date, tank, what was done, by whom, observations, next date. Over time, this record shows how fast sediment returns, which source causes problems, and when the tank is nearing replacement.

Common mistakes with tanks

Draining and refilling only

Without scrubbing, the slime layer stays and recontaminates the new water.

Disinfecting without cleaning

Chlorine cannot reach bacteria protected by sediment and biofilm.

Cleaning the roof tank and leaving the ground tank

The ground tank feeds the roof tank; dirty water from below contaminates the clean tank above within days.

Ignoring the cover

A missing or loose cover lets in dust, insects, birds and light; much of the contamination enters this way.

Entering large tanks without equipment

A real safety hazard; leave it to equipped teams.

Judging water by its appearance

The Sidon study proves clear water can be contaminated.

A short checklist for the homeowner

Covers sealed, vents and overflows screened.
All tanks cleaned on a schedule, with the ground tank included.
A record of dates.
Filters changed on schedule and after cleaning.
Pump and float valves checked.
Extra care after summer absence, tanker deliveries and network works.

Water tank cleaning with Power Zone in Lebanon

Power Zone operates in Lebanon from its office in Mneimneh Building, 5th Floor, Verdun, Beirut, as Power Zone s.a.r.l, registered at the Commercial Register in Beirut and with the Ministry of Finance under registration No. 4090537. In Lebanon, Power Zone builds on Zone 15, the cleaning services brand many clients already know; you can read more on our About page.

Our water tank cleaning service follows the four-step method described in this guide: inspection, physical cleaning, measured disinfection and a check before handover, with a written report. It works alongside our pump, filtration, water heater and leak detection services. Every job follows the same path: your request, a site visit, a clear quotation you approve before work starts, the work itself, and handover with a report. Request a visit. This guide is also available in Arabic.

Frequently asked questions

How often should a water tank be cleaned in Lebanon?

There is no binding Lebanese schedule. As a regional reference, Kahramaa recommends inspecting at least every two months and cleaning and disinfecting at least every six to ten months. Lebanese studies linking heat and storage time to bacterial growth argue for cleaning before and after summer, and immediately after any contamination.

Is tank water in Lebanon safe to drink?

It depends on the source and the tank. A Beirut Arab University study of 50 household tanks in Sidon found bacteriological contamination and concluded the water was unsuitable for drinking, even though chemical indicators were acceptable. Clean tanks, filtration and testing reduce the risk.

Why does water quality get worse the longer it sits in the tank?

Lebanese American University studies found bacterial counts rose markedly after 4 and 7 days of storage, and that counts correlated with temperature, pH and storage time, with the worst results in summer.

What is the correct way to clean a water tank?

WHO Technical Note No. 3 describes four steps: inspection, physical cleaning with sediment removal and scrubbing, disinfection with a measured chlorine solution and contact time, and checking residual chlorine before use.

Can I just add chlorine to the tank instead of cleaning it?

No. Chlorine cannot reach bacteria protected by sediment and slime, and AUB research warns that random dosing creates unwanted disinfection by-products. Disinfection must follow physical cleaning and be measured.

Is tanker water safe?

Tanker water quality varies by supplier and delivery. Ask about the source, check the tanker's cleanliness, never fill a dirty tank, and do not assume tanker water is safe to drink. WHO says tankers themselves must be cleaned and disinfected before use.

Which type of tank is best in Lebanon?

Dark, opaque polyethylene tanks limit algae and are easy to clean. Fibreglass is durable but can roughen with age. Galvanised steel rusts over time. Old asbestos-cement tanks should be replaced when damaged.

Who cleans the shared tanks in an apartment building?

Usually the building committee arranges cleaning of shared ground and roof tanks and decides how costs are shared. Residents can ask for the last cleaning date and the schedule.

What should I do when returning to a house that was closed for months?

Drain, inspect, clean and disinfect the tanks before using the water. Kahramaa's regional guidance recommends chlorinating before use after an absence of more than two weeks.

Why is there sediment in my glass?

Sediment in the tank bottom is stirred up when the pump runs or the tank refills. It means the tank needs cleaning and the filters need changing.

Does a water filter replace tank cleaning?

No. A filter fed by a dirty tank clogs quickly and can become a growth site. Filters work after a clean tank, not instead of one.

Is it safe to clean an underground tank myself?

Underground tanks are confined spaces with risks of low oxygen, gases, slipping and chlorine fumes. Leave them to equipped teams with ventilation, lighting, harnesses and a person outside.

How do I know if my tank is contaminated?

Signs include sediment, cloudy or smelly water, slime on the walls, insects or animals in the tank, a loose cover, and illness in the household. Clear water can still be contaminated; only testing confirms.

What happened with cholera in Lebanon?

In October 2022, Lebanon notified WHO of its first cholera outbreak since 1993, and by 12 November 2022 recorded 3,485 cumulative cases. Cholera spreads mainly through contaminated water or food, which is why clean, sealed tanks matter.

Does Power Zone clean water tanks in Lebanon?

Yes. Power Zone cleans and disinfects roof, ground and underground tanks across Lebanon from its office in Verdun, Beirut, following the four-step method and providing a written report.

How do I book a tank cleaning with Power Zone?

Send a request through the contact page or WhatsApp with the number and type of tanks. We arrange a visit and send a clear quotation for your approval before work starts.

Water tank cleaning in Lebanon: the complete guide