Water Tank Cleaning: Dubai Municipality Rules

Look up the rule for water tank cleaning in Dubai and most pages give the same answer: every six months, with no document named behind it. The interval is roughly right. Everything around it is missing. There is a document, with a code, a version number and an issue date, and it asks for a great deal more than a visit twice a year.

The document behind the rule: DM-HSD-GU44-LCWS2

The rule lives in Dubai Municipality's Technical Guidelines for Legionella Control in Water System, published by the Health and Safety Department, Environmental Health Section. The document code is DM-HSD-GU44-LCWS2. The current edition is Version 6, issued 19 August 2025, superseding the edition of 17 December 2024. It is published as open data on the Municipality's own site at dm.gov.ae/documents/hsd-gu44.

The scope is broad and written as an open list. The guideline applies "to waters used in all built environment including, but not limited to hotels, Professional non-medical service provider premises, educational institutes, commercial, governmental and residential buildings, and labor accommodations". Residential buildings are named. For a private villa, it is the clearest published standard for how a tank should be cleaned, whether or not anyone ever inspects it.

The same section states the consequence in general terms: "Every violator of these guidelines shall hold legal accountability according to local order No. (11) For the year 2003 concerning public health and community safety." No dirham figure appears in the document, or on the Municipality page that publishes it. A contractor quoting a specific fine is quoting something else.

Twice a year, and the clauses almost nobody quotes

Two clauses carry the headline. Section 12-1, on regular maintenance procedures, reads: "All water storage tanks, water heaters (calorifiers), water filters must be emptied, cleaned and disinfected at least twice a year and if legionella is detected in the system." The domestic water checklist at 20-2 adds the strength: "All water storage tanks shall be cleaned and disinfected with 50mg/l chlorine at least twice per year."

That is where most articles stop. Around the twice-yearly clean sits a schedule of much shorter intervals, and those clauses decide whether a tank is in order between visits.

What	The requirement, in the guideline's words	How often
Water storage tanks	"emptied, cleaned and disinfected", with 50mg/l chlorine	At least twice a year, and if legionella is detected
Water heaters (calorifiers)	"kept Clean, drained and disinfected"	At least twice per year
The tank and its coverings	"kept clean and inspected at least monthly. Ensure that all coverings are intact and firmly in place"	Monthly
Water filters	"kept Clean and disinfected regularly, at least monthly", and changed periodically	Monthly
The water system generally	"Regular visual inspections should be made at least every week to avoid the build-up of dirt, organic matter or other debris"	Weekly
Water samples (legionella and aerobic count)	One from the main tank, and one from "each water storage tank with a water storage volume of over 1000 liters" (section 13, Tables 1 and 2)	Quarterly
Shower heads and taps	"kept clean regularly and disinfected at least quarterly"	Quarterly
Taps and showers in unoccupied rooms	run "for several minutes to draw through water"	At least once a week, and always prior to occupation
Hot water, and cold water	50 to 60 degrees, and below 20 degrees	At all times

The sampling row is the one that matters between cleans. Testing is not only something done after a clean: the guideline sets a quarterly minimum for legionella and for the general aerobic count, and requires that "The test results must be available for inspection by the Dubai Municipality staff."

Shower heads and taps have their own clause: kept free from scale and disinfected at least quarterly, a separate job from the tank.

What an inspection looks for before the work starts

The coverings come first. The monthly clause asks that "all coverings are intact and firmly in place", so a lid left ajar or a hatch that no longer seals fails it, whatever the water looks like.

Sediment on the tank floor matters less as dirt than as shelter. The guideline notes that "A detectable population of Legionella bacteria in the water indicates that there will be a larger population in sediments and biofilm within the system", and defines biofilm as "Microbial populations that adhere to and grow on the inside of pipes and other surfaces". A tank can look acceptable and still be coated, which is why the brush goes over the walls as well as the floor.

The guideline treats a bad tank as a hazard to the people cleaning it, not only to the people drinking from it. Section 21 requires that "Pre-disinfection should be carried out if conditions inside water tanks are so poor that they could negatively affect the comfort and health of cleaning personnel." It also requires that "Warning signs and labels indicating that disinfection is in progress must be installed in all water-use areas." In a villa that means every bathroom and the kitchen, and in a building every affected floor.

Finding significant sediment, or evidence of contamination, during a routine inspection is itself a trigger. Disinfection is required "If there is evidence of contamination or significant sediment during the periodic inspection of water storage tanks", so a monthly check that finds either one brings the job forward.

The procedure, step by step

Section 21-1, Cleaning and Disinfection of Water Tanks, gives nine steps. The order is the method.

Empty the tank. "Completely drain all water from the tank before starting the cleaning and disinfection process."
Initial cleaning. "Clean the internal walls and floor of the tank using a soft brush and clean water." Approved cleaning products are used on stubborn deposits.
Rinsing. "Rinse the tank thoroughly with clean water multiple times to ensure all chemicals and sediments are removed."
Preparing the chlorine solution. "Prepare a chlorine solution at a concentration of 50 parts per million (ppm) using chlorine-based disinfectants according to the instructions on the packaging."
Filling the tank. "Fill the tank with clean water up to 3/4 of its capacity, then add the chlorine solution and stir the water thoroughly to ensure even distribution of chlorine." Three quarters, then dose, then stir.
Disinfection. "Allow the water and chlorine solution to remain in the tank for at least 4 [to] 6 hours for disinfection. The chlorine concentration in the water should be maintained between 1 [and] 2 ppm during this period." Holding that range for the whole period means measuring it, not assuming it from the dose, and the guideline's equipment list for the job includes water quality testing devices.
Final rinsing. "After the disinfection period, rinse the tank again thoroughly with clean water to remove all chlorine residues."
Refilling. "Refill the tank completely with clean water, and ensure there are no leaks in the tank or malfunctions in the system."
Quality verification. A sample, sent to an accredited laboratory, "at least 48 hours after refilling".

A hold of four to six hours, on top of draining, brushing, repeated rinsing and refilling, rules out a short visit. Tank capacity, pump rate and the number of tanks move the total, but the hold does not compress.

Cleaning a tank also does not clean the pipes fed by it. The network has its own eight-step procedure at 21-2: a lower chlorine concentration of 1 to 2 ppm, held for at least four to six hours, rinsed, then sampled from various usage points at least 48 hours later. Separately, section 12-1 requires the system to be flushed at least every six months, either with water at 70 degrees or more for five minutes, or with chlorine to a free residual of 1 to 2 mg/l at every outlet.

The laboratory sample taken at least 48 hours after refilling

Step 9 in full: "Collect a water sample from the tank and send it to an accredited laboratory for analysis to confirm water quality and ensure no contamination remains, at least 48 hours after refilling."

This is the step that separates a job from a hose and a brush, and the first thing to look for on a certificate. The guideline does not explain the 48 hours. Its effect is that the sample reflects the tank back in service, rather than the tank on the day of the dose.

Accredited has a specific meaning here. The guideline states that "The analysis of microbiological samples must be undertaken by a laboratory that is accredited by The Emirates International Accreditation Centre (EIAC) to perform the required testing", and points to the accredited list at eiac.gov.ae. It also fixes the methods: legionella "must be detected by culture of viable organisms according to the international standard ISO 11731", with sampling in accordance with BS 7592.

What comes back is not a pass or fail stamp. The guideline sets limits for legionella and for total bacterial count in a hot, warm and cold water system, and a table of action levels against them. Not detected is acceptable. A low detection calls for the risk assessment and control measures to be reviewed and the water resampled, and if a similar count appears again, for cleaning and disinfection and another sample. A high detection calls for immediate cleaning and disinfection of the whole system, with resampling until the count comes down. Where a warm water system returns 1,000 or more colony forming units of legionella per litre, the guideline also requires the owner to submit the report to Dubai Municipality's health and safety department within 24 hours of receiving it. That duty sits with the owner, not the laboratory or the contractor.

Hot above 50, cold below 20, and why temperature is half the problem

Temperature is the other half of the problem, and no amount of tank cleaning substitutes for it. The risk assessment section names the band plainly: areas of concern are those "which contain water at temperatures likely to support the growth of Legionella (i.e. above 20°C but below 50°C)".

Hence the two temperature clauses in section 12-1: hot water kept hot, between 50 and 60 degrees, and cold water kept cold, below 20 degrees, at all times. The domestic checklist is more specific. Hot water storage is held at a minimum of 60 degrees. Calorifier thermostats "should modulate as close to 60 °C as practicable without going below 60 °C", with return temperatures not below 50 degrees, and small water heaters of no greater than 15 litres kept close to 60. Cold water is held below 20 degrees "throughout the system for all outlets".

Cold below 20 at every outlet, at all times, is a plumbing and insulation question rather than a cleaning one. So is the instruction that "All dead legs should be removed or disconnected (stagnant lines and stubs) from the water system", which covers capped spurs left by a bathroom refit and lines to taps nobody uses. Dead legs, a water heater that will not hold temperature and cold runs that warm up are plumbing questions, booked separately from a tank clean and worth settling before the next sample rather than after.

Who is responsible: villa owner, building management, tenant

The guideline is direct about the duty. Section 12 opens: "The owners, principal manager, or person in charge of the premises should comply with their legal duties." Three situations follow.

A villa

The owner is the person in charge of the premises. No management company sits between the tank and the owner, which also means nobody else is keeping the records. A villa owner who keeps the dated certificate and the laboratory result from each clean has the same paper trail the guideline asks of larger premises.

An apartment in a tower

The tanks are common property, so the duty travels with the management of the common parts. Dubai's Law No. (6) of 2019 Concerning Ownership of Jointly Owned Real Property places the management, operation and maintenance of common parts and utility services with the developer or with a specialised management company, depending on the project category. Article 34 provides that "A Management Entity will conclude contracts and agreements with maintenance, security, cleaning, insurance, and other corporations and companies to the extent required to enable it to perform its duties". The same law sets up an Owners Committee, whose duties include checking that the management entity complies.

For a tenant, that turns a vague complaint into a specific letter. Write to the building's management entity (the developer or the management company), copying the owners committee, and ask for two documents: the current water tank cleaning and disinfection certificate, and the water test results. Both are named in the Municipality's own compliance checklist, and test results must be available for inspection by Dubai Municipality staff. A building that cannot produce them has answered the question already.

A property that stood empty: the flushing clause

Stagnation is treated as its own hazard, with its own clause. The flushing policy in section 12-1 reads: "The premise shall have Flushing policy and run all taps and showers in guest rooms and other areas for several minutes to draw through water at least once a week if rooms are unoccupied, and always prior to occupation."

Several minutes, weekly, and always before anyone moves in. The wording is written with guest rooms in mind, but the logic carries to a villa closed while the family travels, a unit standing empty, a maid's bathroom nobody uses. Where a system has been idle longer, the guideline moves past flushing: disinfection is required "If the hot and cold water system has not been used for an extended period, has not been drained as recommended, or if control measures have been ineffective for a long time." Running the taps for a few minutes is not the same as disinfecting the system.

What to ask a contractor before booking

The procedure above is specific enough to hold a quote against. Six questions, all answerable from the document above, and by a competent contractor in one message:

What chlorine concentration goes into the tank, and what goes into the network? The guideline says 50 ppm for the tank, 1 to 2 ppm for the distribution system.
How long is the hold, and is the residual checked during it? At least four to six hours, maintained at 1 to 2 ppm.
How many rinses? Several before dosing, until the chemicals and sediment are gone, and a final rinse after the hold.
When is the sample taken? At least 48 hours after refilling, not on the day.
Which laboratory, and is it EIAC accredited?
Will the certificate be dated, and do the test results come with it?

A crew that arrives, drains, brushes, refills and leaves inside an hour has not carried out the procedure in section 21-1, whatever the certificate says afterwards. The hold alone rules it out.

Booking a tank clean

The guideline asks for notice before the work: building occupants and maintenance teams told about the procedure and any disruption to the water supply. Tank work is best booked a day or two ahead for that reason, so residents can be told and the supply can be off for the length of the hold.

OUSIS cleans water tanks to the Dubai Municipality standard with licensed technicians: inspection, draining, disinfection and refill. Details are on the water tank cleaning page, and a clear quote comes on WhatsApp, usually within the hour. Settle the laboratory sample at the same time as the booking: who collects it, which EIAC-accredited laboratory analyses it, and the date it will be drawn.

Two dates then decide whether a tank is in order: the date on the last cleaning and disinfection certificate, and the date the sample behind it was taken. The second should fall at least two days after the refill. With an accredited laboratory's result attached, the paperwork describes the water coming out of the taps, not only the chlorine that went into the tank.

Questions people ask

How often should water tanks be cleaned in Dubai?

Dubai Municipality's legionella guideline, DM-HSD-GU44-LCWS2, requires water storage tanks to be emptied, cleaned and disinfected at least twice a year, and again whenever legionella is detected. Between cleans, the tank should be inspected monthly with its covers intact, the wider system checked visually every week, and water samples taken at least quarterly for legionella and aerobic bacteria.

What chlorine concentration does Dubai Municipality require for tank disinfection?

The guideline's domestic water checklist asks for storage tanks to be disinfected with 50mg/l chlorine at least twice a year. In the step-by-step procedure, a 50 ppm solution is added once the tank is three quarters full, and the concentration in the tank is held between 1 and 2 ppm for at least four to six hours before the final rinse.

When should the water sample be taken after a tank clean?

At least 48 hours after the tank has been refilled. The sample goes to a laboratory accredited by the Emirates International Accreditation Centre, and legionella is tested by culture under ISO 11731. A sample drawn on the same day as the clean does not meet that step, so the certificate date and the sample date are worth comparing.

Who is responsible for water tank cleaning in a Dubai apartment building?

In a jointly owned building the tanks are common property, managed by the management entity under Law No. (6) of 2019: the developer or a specialised management company, depending on the project. A tenant with concerns should write to that entity, copying the owners committee, and ask for the current cleaning certificate and the latest water test results.

What should I ask a water tank cleaning company in Dubai?

Ask how the job follows the procedure in section 21-1 of the Dubai Municipality guideline: the chlorine strength (50 ppm for the tank, 1 to 2 ppm for the pipework), how long the hold lasts and whether the residual is measured during it (at least four to six hours at 1 to 2 ppm), how many rinses, which EIAC-accredited laboratory tests the water, and when the sample will be drawn (at least 48 hours after refilling). A crew that is in and out within the hour has not followed the procedure.

Is there a fine for not cleaning a water tank in Dubai?

The guideline states that violators are held legally accountable under Local Order No. 11 of 2003 on public health and community safety. It does not publish a fine amount, and no figure appears on the Dubai Municipality page that hosts the document. Any contractor quoting a specific penalty should be asked which document it comes from.

What Dubai Municipality actually requires of a water tank, and how a clean is done