Why Legionella is a building problem, not a supply problem
Legionella is a group of bacteria that lives naturally in water in small numbers. In a well-run supply network it rarely causes trouble. The risk begins inside buildings, where water is stored, warmed, left standing and sprayed through showers, cooling towers, fountains and misters. That is why Dubai Municipality addresses Legionella through guidelines for the people who own, manage and maintain building water systems, rather than through the public supply alone.
Dubai Municipality's Technical Guidelines for Legionella Control in Water System describe the change clearly. Once water from the public network enters a building, it meets warmer temperatures, slower flow, periods of stagnation and longer residence times, and the disinfectant it carried can fade. Biofilm forms on the inside of pipes, valves and fittings, and Legionella can shelter and multiply inside that slime, protected from the conditions that would otherwise control it.
The illness linked to these bacteria is called legionellosis. The serious form, Legionnaires' disease, is a type of pneumonia that mainly affects people who are more vulnerable because of age, illness, a weakened immune system or smoking. A milder, flu-like form is known as Pontiac fever. The guideline notes that Legionnaires' disease develops within 2 to 10 days after exposure, which is one reason why records and fast reporting matter so much when a case is suspected.
People are infected mainly by breathing in fine droplets or aerosol from contaminated water, not simply by seeing or touching water. A shower head, a cooling tower drift plume, a decorative fountain or a mist fan can all release that aerosol. The practical message for building owners in Dubai is simple: the water may arrive in good condition, but what happens to it after the meter is the building's responsibility, and the controls described below are what keep it safe.
This guide explains the main requirements of the guideline in plain language for owners, building managers, facility teams and tenants who want to understand what should be happening in their building. It is based on version 5 of the guideline, issued on 17 December 2024. Dubai Municipality also lists a later revision, so the current version should always be checked with the Municipality before it is used as a compliance reference.
Which buildings and water systems the guideline covers
The guideline states that it applies to water used in the built environment, including but not limited to hotels, professional non-medical service premises, educational institutes, commercial, governmental and residential buildings, and labour accommodation. Its stated objective is to minimise the risk of exposure to Legionella through safe operation, proper maintenance and scheduled monitoring of building water systems in public establishments such as hotels, furnished apartments, residential buildings, malls, schools and government buildings.
It also sets out the legal basis. The guideline says that every violator holds legal accountability under Local Order No. 11 of 2003 concerning public health and community safety in the Emirate of Dubai. It adds that if Dubai Municipality is satisfied that a high-risk water system is not being maintained as required, it may give the owner written notice to shut the system down immediately or to take specified action within a set time.
The systems in scope are wider than most people expect. They include cooling towers and evaporative condensers, hot, warm and cold domestic water systems, fountains, waterfalls and water features indoors and outdoors, spa pools, whirlpool spas and jacuzzis, evaporative air coolers, misters, air washers and humidifiers, and irrigation and grey-water systems. The guideline also mentions car and bus washes and wet scrubbers as systems that can present a risk.
A key principle is that each water system must be treated as a whole. The guideline explains that a system includes all associated pipework, pumps, feed tanks, valves, showers and heat exchangers, and that a cooling tower, for example, should not be considered in isolation. In practice this means a tank cleaning certificate on its own does not show that a building is under control; the pipes, heaters, outlets and records all form part of the picture.
The conditions Legionella needs to multiply
The guideline lists the conditions that favour the growth of Legionella: water temperatures between 20 and 45 degrees Celsius, high nutrient levels, the accumulation of organic material, sediment and other organisms, water stagnation, pH fluctuations, inadequate levels of disinfectant, and changes in water pressure. It also notes that the bacteria have been found in water between 6 and 60 degrees Celsius, so the warm middle range is the danger zone rather than the only place they can survive.
Dubai's climate makes the temperature point especially important. Cold water that is meant to stay cool can warm up in rooftop tanks, in risers and in pipes that run through hot ceiling voids or external walls, and the hottest months push stored water further into the growth range. A building that keeps its hot water hot and its cold water genuinely cold removes the single most important condition the bacteria need.
Stagnation is the second big factor. Water that stands still in an unused shower, a guest room that has been empty for weeks, a dead-end pipe left behind after a renovation or a tank that is oversized for the building gives bacteria time to multiply and lets disinfectant fade. Sediment, scale and sludge in tanks and heaters add nutrients and shelter, which is why cleaning and flushing appear again and again in the guideline.
Biofilm ties these factors together. The guideline describes it as a thin layer of micro-organisms that forms as a slime on surfaces in contact with water. Biofilm, sludge and scale can protect Legionella from temperatures and disinfectant levels that would kill or inhibit free-floating bacteria. A water sample that shows no Legionella therefore does not prove that a system is clean, because the bacteria may be attached to surfaces rather than floating in the water.
Temperature control: the first line of defence
The guideline recommends that hot water be stored at 60 degrees Celsius and distributed so that, after one minute of running, a temperature of at least 50 degrees Celsius is reached at the outlets. Cold water storage and distribution should be at 20 degrees Celsius or below. Its domestic water checklist repeats the point: keep hot water hot and circulating at 50 to 60 degrees throughout the system, with storage at a minimum of 60 degrees, and keep cold water below 20 degrees at all outlets.
For central water heaters, called calorifiers, the guideline asks for the flow temperature to modulate as close to 60 degrees as practicable without going below it, and for the return temperature not to fall below 50 degrees. For small water heaters of no more than 15 litres, it says the water temperature should be kept close to 60 degrees. Hot water circulation pumps should run continuously rather than recycling only to mixing valves.
High temperatures bring a scalding risk, especially for children, older people and people with reduced sensation. The guideline recognises this by defining warm water as heated water delivered at around 45 degrees Celsius for sanitary purposes to prevent scalding, and by noting that hot water systems may include thermostatic mixing valves close to sanitary outlets. The usual approach is to keep the system itself hot and to blend the water down only at or near the point of use.
Temperature checks are simple and should be routine. A building team can measure the hot water at a sentinel outlet after one minute of running, the cold water at the same outlets, and the temperatures leaving and returning to each calorifier. The guideline's daily record template asks for hot and cold water temperatures at outlets in at least four different locations or floors each day, alongside disinfectant readings at the main and roof tanks.
Water tanks, heaters and filters: cleaning and inspection
Stored water is where many problems start. The guideline requires that all water storage tanks, water heaters and water filters be emptied, cleaned and disinfected at least twice a year, and again if Legionella is detected. Its checklist adds that storage tanks should be cleaned and disinfected with 50 milligrams per litre of chlorine at least twice per year, kept clean, and inspected at least monthly with all coverings intact and firmly in place.
Filters need more frequent attention than tanks. The general checklist says that all water filters should be kept clean and disinfected regularly, at least monthly, and changed periodically. A neglected filter or water softener can become a home for biofilm, which is why the sampling table also calls for a swab sample from each softener and filter.
The guideline also asks buildings to use a supplementary automatic chlorine dosing system at the water tank connected directly to the main supply, so that a free chlorine concentration of 0.2 to 0.5 milligrams per litre reaches the terminal points. It notes that chlorine works best below a pH of 7.6, and that the level commonly maintained for continuous treatment of domestic drinking water is between 0.2 and 0.5 milligrams per litre at the point of delivery.
The cleaning method matters as much as the frequency. The guideline describes draining the tank to a designated drain, flushing the inlet by opening the float valve fully, physically cleaning the tank without damaging its coating, removing residual sludge with a wet and dry vacuum, refilling, disinfecting, drawing the disinfectant through to the heaters and outlets, testing far outlets to confirm the target concentration, holding it for the contact period, then neutralising and flushing before the system returns to service. Signs and outlet warning labels should be fitted while disinfection is under way.
For tenants and owners, the visible proof of this work is a valid tank cleaning and disinfection certificate, which the guideline lists among the documents a building should hold. The guideline's checklist also requires that the water system cleaning and maintenance company be approved by Dubai Municipality, and that the building hold a valid maintenance contract with an approved company.
Dead legs, flushing and outlets that are rarely used
A dead leg is a section of pipework that does not allow water to flow, such as a capped branch left behind after a bathroom was removed or a stub that once fed equipment. The guideline is direct: all dead legs, stagnant lines and stubs should be removed or disconnected from the water system. Renovations and fit-outs are the most common source of new dead legs, so they should be checked at every handover.
Outlets that are used rarely create the same problem in a different way. The guideline requires a flushing policy: run all taps and showers in guest rooms and other areas for several minutes to draw water through at least once a week if rooms are unoccupied, and always before occupation. For hotels, furnished apartments and buildings with empty units, a simple flushing log with dates and outlets is the easiest way to show this is being done.
Shower heads and taps deserve their own attention because they produce the fine spray that people breathe in. The guideline asks for them to be kept clean and free from scale, and disinfected at least quarterly and whenever Legionella is detected. When results are being investigated, it also calls for swab samples from the back of selected shower heads and water filters after removal.
Beyond routine flushing, the guideline sets a periodic system flush. Hot, warm and cold water systems should be flushed at least every six months, and whenever Legionella is detected, with water of not less than 70 degrees Celsius for five minutes or an equivalent temperature and time combination, or treated with chlorine to give a minimum free chlorine residual of 1 to 2 milligrams per litre at all outlets. Its inspection section adds disinfection at least every six months with 1 to 2 milligrams per litre of free chlorine for one hour, with each outlet allowed to flow for at least five minutes.
Cooling towers and evaporative condensers
Cooling towers and evaporative condensers bring air and water into direct contact to cool the water, and a small amount of water escapes as drift in the exhaust air. That drift can carry aerosol, which is why the guideline says transmission through cooling towers and evaporative condensers has been the most documented route for Legionnaires' disease. Large district cooling plants are outside the scope of a typical building team, but many hotels, malls and older commercial buildings still operate their own towers.
The guideline requires that any cooling water system, including its make-up water tanks, be fitted with an automatic biocide dosing device that works properly throughout the year to manage corrosion, scaling, fouling and microbial growth. The tower should be located so that drift is directed away from air intakes, operable windows and building entrances, and it must be fitted with drift eliminators.
Cleaning is set at least every six months. All cooling water systems, including their tanks, pumps, pipes, water filters and fittings, must be emptied, cleaned and disinfected at least once every six months and whenever Legionella is detected. The inspection section adds that the water treatment system should be inspected at least monthly by a competent person, that total bacteria counts should be tested at least monthly, and that a system shut down for more than four days should be cleaned before it is restarted.
The guideline gives working biocide levels as a reference for consistent control between cleanings: continuous minimum free chlorine residuals of 0.5 to 1 milligrams per litre, or bromine residuals of 1 to 2 milligrams per litre. It recommends that a qualified water treatment specialist define and oversee the treatment programme, and it is clear that testing is not a substitute for sound maintenance and water treatment.
Fountains, spa pools, misters and evaporative coolers
Decorative water features are popular in Dubai lobbies, courtyards and villa gardens, and the guideline treats them seriously because they can produce spray and are exposed to dust, debris, people and animals. Fountains and water features, including their make-up tanks, should have automatically controlled water treatment, be continuously treated with 1 to 2 milligrams per litre of chlorine or 2 to 3 milligrams per litre of bromine, have biocide levels and pH recorded at least three times a day, and be cleaned and disinfected once a week.
Spa pools, whirlpool spas and jacuzzis carry the same treatment levels and a stricter routine. The guideline's checklist calls for biocide and pH monitoring at least three times per day, replacement of at least half of the water every day, daily backwashing of sand filters, and cleaning and disinfection of the whole system once a week, with a working biocide dosing system and daily records.
Evaporative air coolers trickle water over a medium and recirculate it from a sump, which creates the potential for microbial growth. The guideline's practical instruction is that evaporative coolers should be kept dry when not in use. Misters, air washers and humidifiers fall into the same family of aerosol-producing equipment and should be included in the building's risk assessment.
For these systems the guideline sets the strictest microbiological target: Legionella should be less than 1 colony-forming unit per litre, meaning not detected, and a total bacterial count above 500 per millilitre may indicate that maintenance is not satisfactory. Swimming pool water quality is covered by separate Dubai Municipality guidelines, which the Legionella guideline says should be followed for other microbiological and chemical parameters.
The Legionella risk assessment: what it must contain
The guideline describes carrying out a Legionella risk assessment and keeping it up to date as a key duty. It should be repeated periodically, at least once a year, and whenever the system changes or there is reason to suspect a problem. In practice it is the document that ties everything else together: it explains what water systems exist, where the risks sit, who is responsible and how control is checked.
According to the guideline, the assessment should consider a clear allocation of management responsibilities, the competence and training of key personnel, a description of the water system with an up-to-date schematic diagram, an evaluation of the factors that promote Legionella growth, safe operating procedures and controls, monitoring, inspection and maintenance procedures, the results of checks carried out, and arrangements for regular review.
Two layouts are specifically required. The first shows the water system itself, including plant and equipment, servicing and control valves, outlets, strainers, filters and parts that are out of use. The second shows the locations of sampling points chosen according to the risk assessment survey of all water systems that pose a risk to human health. Without these drawings, sampling tends to be random and the results are hard to interpret.
The assessment should identify the risk in each type of system present: hot, warm and cold water, cooling towers and evaporative condensers, fountains and water features, spa pools and jacuzzis, and other systems such as humidifiers, evaporative coolers, misters, air washers, irrigation and grey water. The guideline highlights the factors that raise risk: water between 20 and 50 degrees, places where aerosol is released, infrequently used pipework, stagnant or slow-moving water and dead legs, and water that is not treated.
Who is responsible inside the building
The guideline places the duties on the owners, principal manager or person in charge of the premises. It requires a named person responsible for Legionella control, and that person must be trained in Legionella control, with the training and the name documented. Many problems in practice come from responsibility that is spread across a facility manager, a maintenance contractor, a tank cleaning company and a laboratory without anyone owning the whole picture.
A practical way to organise this is to write down, in one page, who does each task: who reads temperatures and disinfectant levels daily, who inspects tanks monthly, who arranges six-monthly cleaning and flushing, who collects samples and from where, which accredited laboratory analyses them, who reviews the results, and who reports to Dubai Municipality if a result exceeds the limits. That page then becomes part of the risk assessment and the building's records.
Owners who use an annual maintenance contract should check that the contract actually covers these tasks rather than assuming it does. Water system cleaning, disinfection and Legionella sampling are often separate scopes from general plumbing maintenance. The guideline's checklist expects a valid water system maintenance contract with an approved company for cleaning and disinfection, so the contract wording itself is part of compliance.
Tenants in a building usually do not control the central water system, but they still benefit from understanding it. A tenant can reasonably ask the building management when the tanks were last cleaned and disinfected, whether there is a valid certificate, when the system was last tested, and what the hot water temperature at the taps should be. The answers show quickly whether a building has a working control programme.
Testing: what is sampled, where and how often
The guideline requires sampling and testing for both general aerobic bacteria and Legionella, at points chosen according to the risk assessment. For all water systems except cooling water, Legionella and aerobic counts are recommended quarterly. For cooling water, Legionella is tested quarterly and the aerobic count monthly. Testing for Legionella must be done by culturing viable organisms according to the international standard ISO 11731, and the sampling method should follow BS 7592.
Its minimum sampling table for hot, warm and cold water systems is specific. Each quarter, a building should take at least one sample from the main water tank connected to the supply, one from each other tank or cistern holding more than 1,000 litres, one from each central water heater, at least two from hot water taps, two from cold water taps and two from showers on different floors, rooms or locations, and a swab sample from each softener and filter.
Cooling towers need a sample from each make-up water tank and each collection basin. Fountains and water features need one from each collection basin, whirlpool spas and jacuzzis one from each pool, irrigation systems one from each storage tank and from any irrigation water jet, and other systems such as hydrotherapy pools and humidifiers one from each system. During an investigation or after adverse results, four to six sets of swabs should be taken from the back of shower heads and water filters.
The analysis must be carried out by a laboratory accredited by the Emirates International Accreditation Centre to perform the required tests, and the results must be available for inspection by Dubai Municipality staff. The guideline points readers to the accreditation centre's website for the list of accredited laboratories, which is the simplest way for an owner to check a laboratory named on a report.
Reading results: limits and the actions they trigger
For hot, warm and cold water systems, the guideline sets a Legionella reference limit of not more than 1,000 colony-forming units per litre and a total bacterial count of 500 per millilitre, above which maintenance practices may not be satisfactory. For cooling water systems the Legionella limit is also 1,000 per litre, with a total bacterial count below 10,000 per millilitre. For fountains, spas, misters, humidifiers and similar equipment, Legionella should not be detected.
The action table for domestic water is graded. If Legionella is not detected, the result is acceptable. Above 100 and up to 1,000 per litre, the building should review its risk assessment and control measures and resample; if a similar count is found again, the system should be cleaned and disinfected and resampled, with remedial action continuing until results fall below 100 per litre. Above 1,000 per litre, the whole hot, warm and cold system should be cleaned and disinfected immediately and resampled, with temperatures and dosing reviewed and remedial action continued until results fall below 100 per litre.
Cooling towers have their own table combining aerobic counts and Legionella. Below 5,000 aerobic count per millilitre with no Legionella detected is acceptable. In the middle bands the building reviews dosing, biocide levels and pH, reviews the risk assessment and resamples, cleaning and disinfecting the tower if the count repeats. Above 100,000 per millilitre or above 1,000 Legionella per litre, the tower should be turned off, cleaned and disinfected immediately, an alternative biocide added, and the tower restarted only when resampling shows Legionella below 100 per litre and an aerobic count below 10,000 per millilitre.
The guideline also reminds owners that results must be read with care. A detectable Legionella population in the water suggests a larger population in sediment and biofilm, while an undetected result may not mean the system is free of the bacteria. It concludes that monitoring the overall bacterial level is often more useful for managing a system than Legionella data alone, and that monitoring never replaces inspection, maintenance and cleaning.
Records, online submissions and the 24-hour reporting rule
Good records are what turn maintenance into evidence. The guideline lists the documents a building should keep: a formal risk assessment and scheme of control, the sampling point layout, system schematics and operating and maintenance manuals, the system water volume with the date and method used to determine it, inspection and maintenance dates and results, details of treatment and biocides with safety data sheets, the names of people responsible for operation and shutdown, and the results of all testing.
Daily record templates are included in the guideline for hot and cold water systems, cooling water systems, fountains and spas. They capture disinfectant readings, temperatures and, for cooling towers and features, ORP values. Version 5 of the guideline states that these records must be available for inspection and submitted every two weeks to the email address given in the document, and its checklist says the required reports should be submitted online through Dubai Municipality's Building Health and Safety Compliance Test Reports e-service.
Two reporting duties have strict deadlines. If the owner of premises with a cooling water system or a warm water system receives a laboratory report showing 1,000 or more colony-forming units of Legionella per litre, the guideline says the report must be submitted to Dubai Municipality's health and safety department within 24 hours of receiving it. The person in charge must also report to the department within 24 hours if any confirmed case of legionellosis occurs in the premises.
Because these deadlines are short, the communication path from the laboratory to the person responsible should be agreed in advance. The guideline itself advises owners of high-risk systems to establish an effective process for the rapid provision of microbiological results from the laboratory, so that a high result does not sit in an inbox over a weekend.
Outbreak plans and emergency decontamination
The guideline asks the owners, principal manager or person in charge to establish an emergency plan to protect public health and prevent further infection. It defines an outbreak as two or more confirmed cases of legionellosis occurring in the same locality within a six-month period. The plan should name the trained team and their responsibilities, command and control points, indoor and outdoor assembly areas, and communication procedures with mobile numbers and email addresses.
Emergency procedures in the plan include shutting down any process that can generate and spread airborne water droplets until sampling and remedial work have been done, taking water samples before any emergency disinfection, providing staff health records to identify undiagnosed cases, and co-operating fully with any investigation, including tracing pipe runs and reviewing operating records in detail.
Emergency decontamination is required when a system is suspected of being associated with an outbreak, or when it is known or suspected to contain more than 1,000 Legionella per litre in a warm water system or a cooling tower. For cooling towers the guideline describes shutting the system off, isolating the fans, circulating a dispersant, dosing sodium hypochlorite to hold a free chlorine residual of 5 to 10 milligrams per litre at pH 7.0 to 7.6 for at least 60 minutes with checks every 15 minutes, draining and cleaning, refilling and re-dosing, then draining, refilling and recommissioning with the treatment programme reinstated.
For hot, warm and cold water systems, emergency decontamination means flushing with water of not less than 70 degrees Celsius for five minutes, with a minimum of 60 degrees measured at the outlets, and disinfecting with chlorine to give a free chlorine residual of 1 to 2 milligrams per litre for one hour, with each outlet allowed to run for at least five minutes. These are specialist procedures with chemical and scalding hazards, so they should be carried out by trained teams following a written method.
Villas and smaller buildings: applying the same principles
The guideline is written mainly for public establishments and buildings such as hotels, residential buildings, schools, malls and labour accommodation, and the full sampling, reporting and record-keeping duties are designed for those premises. A private villa is a different scale of system, but the physical risks are the same: warm stored water, tanks on the roof, rarely used bathrooms, garden water features and misting fans.
For a villa, the guideline's principles translate into a few sensible habits. Keep the water heater set so that stored water reaches around 60 degrees and use mixing valves where scalding is a concern. Make sure roof and ground tanks have intact, firmly fitted covers and are cleaned and disinfected regularly by a qualified company. Run the taps and showers in guest rooms and unused bathrooms for several minutes every week, and always after the house has been empty, for example after a summer holiday.
Garden water features, outdoor misting systems and evaporative coolers deserve the same attention as in a hotel, scaled to the household. Keep them clean, treat the water as the manufacturer recommends, drain and dry evaporative coolers when they are not in use, and descale and clean shower heads regularly. If anyone in the household is more vulnerable, these simple steps matter even more.
Owners who rent out a villa or apartment should also think about the gap between tenancies. A property that stands empty for weeks in the Dubai summer accumulates stagnant, warm water in every pipe. Flushing all outlets before the new tenant moves in, checking the hot water temperature and confirming when the tanks were last cleaned are small steps that protect both the tenant and the owner.
Common gaps found when buildings review their water systems
When a building compares its daily practice with the guideline for the first time, the same gaps tend to appear. Roof tanks have covers that no longer close properly, or vents without screens. Cold water at outlets on upper floors runs warm for a long time before it cools, because the tanks and risers sit in the heat. Water heaters have been turned down to save energy, so stored water never reaches 60 degrees. Showers in staff rooms, gyms or empty units have not been run for weeks.
Other gaps are hidden in the pipework and the paperwork. Fit-out works have left capped branches that nobody removed. A filter or softener has not been opened since it was installed. A cooling tower dosing pump has failed and nobody noticed because the daily record was not being kept. The tank cleaning certificate is valid, but there is no risk assessment, no schematic and no sampling plan, so nobody can say which outlets were tested or why.
None of these findings is unusual, and each has a straightforward fix. The value of a structured review is that it turns a vague worry about water quality into a short, prioritised list: what to correct this week, what to schedule this month and what to build into the annual maintenance plan.
Energy saving and Legionella control: getting the balance right
Dubai buildings are rightly encouraged to save energy, and water heating is an obvious target. The difficulty is that lowering hot water temperatures to save energy moves stored water into the range where Legionella multiplies. The guideline's temperatures are clear: storage at 60 degrees, at least 50 degrees at outlets within one minute and calorifier returns not below 50 degrees. Energy measures should be designed around those temperatures, not against them.
The safer savings come from reducing heat loss rather than lowering set points: insulating hot water pipes and tanks, keeping circulation pumps running so that water does not cool in long branches, sizing storage to the real demand of the building so that water turns over rather than standing, and repairing leaking taps and cisterns that waste heated water. Cold water benefits from the same thinking, with insulation and routing that keep pipes away from hot ceiling voids and sun-exposed walls.
Any change to the hot water system, from a new heater to a new timer schedule, is a change to the water system and should be reflected in the risk assessment. A short check of outlet temperatures after the change confirms that energy has been saved without creating a new risk.
Choosing contractors and laboratories you can rely on
The guideline sets several expectations that help owners choose the right partners. The water system cleaning and maintenance company should be approved by Dubai Municipality. Microbiological analysis should be done by a laboratory accredited by the Emirates International Accreditation Centre. The person responsible for Legionella control in the building should be trained, with the training documented. Each of these can be checked on paper before work starts.
When comparing proposals, owners can ask each contractor to show which tasks from the guideline are included: six-monthly cleaning and disinfection of tanks, heaters and filters, monthly tank inspection, periodic system flushing, quarterly disinfection of shower heads and taps, sampling at the points named in the risk assessment, and support with records. Quotes that simply say tank cleaning without describing the method, chlorine level, contact time and certificate are hard to compare.
Owners should also ask what happens after a high result. A good contractor explains how resampling, cleaning, disinfection and reporting would be organised, who would contact Dubai Municipality within the 24-hour window, and how the building would be kept informed. That conversation reveals more about competence than any brochure.
Dubai Municipality's Health and Safety Department publishes approved company lists, and owners can ask any contractor for proof of the approvals that apply to the specific work being quoted. Keeping copies of approvals, certificates, laboratory accreditation and test reports in one file makes inspections and handovers far easier.
A year-round Legionella control calendar for Dubai buildings
Daily: record hot and cold water temperatures at representative outlets and disinfectant levels at the main and roof tanks, as the guideline's record templates show. For cooling towers, fountains and spas, record disinfectant levels, pH and the other parameters the templates list, three times a day where the guideline requires it.
Weekly: carry out visual inspections to prevent the build-up of dirt, organic matter and debris, as the guideline recommends at least every week. Run all taps and showers in unoccupied rooms for several minutes. Clean and disinfect spa pools, whirlpool spas, jacuzzis, fountains and water features once a week, and keep evaporative coolers dry when they are not in use.
Monthly: inspect water storage tanks and check that covers are intact and firmly fixed, clean and disinfect water filters, have a competent person inspect cooling water treatment systems, and test cooling water for total bacterial count. Review the daily records and follow up any reading outside the target range.
Quarterly and twice a year: take the quarterly Legionella and aerobic samples at the points named in the risk assessment, and disinfect shower heads and taps. At least every six months, empty, clean and disinfect tanks, water heaters and filters, flush and disinfect the hot, warm and cold system, and empty, clean and disinfect cooling water systems. At least once a year, and after any change, review and update the risk assessment.
How Power Zone Dubai supports building owners
Power Zone Dubai provides water tank cleaning, plumbing, water heater maintenance and commercial building maintenance from its office in Business Bay, across all seven emirates, with 20 in-house teams. For owners and facility managers, the most useful starting point is usually a site survey that maps the water systems, tanks, heaters, outlets and records against the checklist in this guide.
From there, the work can be organised into a calendar that matches the guideline: tank and heater cleaning and disinfection, flushing and outlet maintenance, dead-leg removal after renovations, and the records that show the work was done. Owners can request a quotation through the Dubai prices page or by contacting the Dubai office on WhatsApp.
Whichever contractor a building uses, the principle is the same. Legionella control in Dubai is not one cleaning visit a year but a system of temperatures, cleaning, flushing, testing, records and fast reporting, owned by a named, trained person. Buildings that run that system well protect their residents, guests and staff, and are ready when Dubai Municipality inspects.
Frequently asked questions
Does Dubai Municipality require Legionella testing in buildings?
Dubai Municipality's Technical Guidelines for Legionella Control in Water System require sampling and testing for both Legionella and general bacteria at points chosen in the building's risk assessment, recommended quarterly for most systems, with monthly aerobic counts for cooling water. Results must be available for inspection by Dubai Municipality staff.
How often must water tanks be cleaned in Dubai?
The guideline requires water storage tanks, water heaters and filters to be emptied, cleaned and disinfected at least twice a year and whenever Legionella is detected, with tanks inspected at least monthly. It also expects a valid tank cleaning and disinfection certificate and an approved cleaning company.
What temperature should hot water be to control Legionella?
The guideline recommends storing hot water at 60 degrees Celsius and distributing it so that at least 50 degrees is reached at outlets after one minute of running. Cold water should be stored and distributed at 20 degrees or below. Mixing valves near outlets help manage the scalding risk.
Who can test water for Legionella in Dubai?
The guideline requires the analysis to be carried out by a laboratory accredited by the Emirates International Accreditation Centre to perform the required testing, using culture methods according to ISO 11731, with sampling following BS 7592.
What happens if a test shows more than 1,000 Legionella per litre?
For hot, warm and cold water, the guideline calls for immediate cleaning and disinfection of the whole system, resampling and a review of controls. For cooling or warm water systems, the owner must submit the laboratory report to Dubai Municipality's health and safety department within 24 hours of receiving it.
How often should a Legionella risk assessment be done?
The guideline asks for a periodic risk assessment of water systems at least once a year, and whenever the system changes or there is reason to suspect a problem. It should include responsibilities, a system schematic, sampling point layouts, procedures, monitoring results and review arrangements.
Can Legionella be found even if the water looks clean?
Yes. Legionella cannot be seen or smelled, and the guideline notes that it can shelter in biofilm, sediment and scale. A sample with no Legionella detected does not always mean a system is free of the bacteria, which is why cleaning, temperature control and flushing matter as much as testing.
Does the guideline apply to private villas?
The guideline is written mainly for public establishments and buildings such as hotels, residential buildings, schools and malls. Private villas face the same physical risks, so keeping hot water hot and cold water cold, cleaning tanks regularly, flushing unused outlets and maintaining water features are sensible habits for any home.
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