Legionella control for hotels and buildings in Thailand: the part a lab test can't do
A six-monthly sample tells you what the water was like on one day. A risk assessment, a written control scheme and a monitoring routine keep it under control on the other 180. Envirisk Asia provides that second part, to the UK standard, from Bangkok.
Hotels and resorts, hospitals, offices and malls, factories, condominiums. Thailand first; Vietnam, Malaysia, Singapore, Indonesia and the rest of Southeast Asia on request.
- 229
cases of Legionnaires' disease were linked to stays in Thailand between 2013 and September 2024. 97% were foreign visitors; the UK was the largest source.Division of Epidemiology, 2025
- 28%
of the 50 hotels the Department of Health sampled in 2025 had Legionella in their water. Six months and a training round later, a third of those were still positive.Department of Health, 2026
- 44
accommodation visits in Thailand were triggered by the European surveillance network in 2023, joint second among all non-EU destinations. Each one starts with a sick guest and a phone call to the hotel.ECDC, 2023
Testing is not control
Most buildings in Thailand manage Legionella the same way: a contractor takes samples twice a year, the engineer drops chlorine tablets in the tank, and a certificate goes on the wall. Every one of those things is useful. None of them tells you where the bacteria will grow next, or proves to an auditor that you are in control.
What most properties have
- A lab sample every six months, usually taken by the maintenance contractor
- Chlorine tablets in the tank, dosed by habit rather than measurement
- A cooling tower chemical contract that covers scale and corrosion
- Showerheads cleaned when someone remembers
- No written plan, no named person, no records an auditor can read
What an assessment adds
- A survey and schematic of every water system, from the borehole to the furthest shower
- Risk scored system by system, with the actions ranked by what matters most
- A written scheme: who checks what, how often, and what counts as a fail
- Chlorine and temperature logs of the kind Department of Disease Control investigators and tour-operator auditors ask to see
- Sampling that is independent of the contractor who treats the water
In March 2025, Thai investigators visited a certified 248-room hotel in Phuket after three European guests fell ill. Two contractors had been testing it regularly, with clean results. The cooling towers were heavily contaminated. The investigators' recommendation: have sampling done by someone other than the maintenance contractor.How our approach differs
Legionella risk assessment
Time on site depends on the size of the property. Every water system surveyed and drawn, temperatures and chlorine measured at the points that matter, each risk scored, and a report that says exactly what to fix first. Carried out to the BS 8580-1 and HSG274 method used in the UK, mapped to the checks your auditors make.
- System schematics
- Scored risk register
- Prioritised action plan
- Written scheme of control
- Report in English, Thai summary on request
Water safety plans and monitoring
The plan that keeps the assessment alive: control limits, daily and weekly checks, logbooks your engineers will actually fill in, training for the responsible person, and review visits. Includes the procedure for closing wings in low season and bringing them back safely.
- Written water safety plan
- Check sheets and logbooks
- Responsible-person training
- Quarterly or six-monthly review visits
- Independent sampling at TEST TECH (ISO 11731:2017), IMC Thai (AS 3896:2017) or a Department of Medical Sciences Regional Medical Sciences Center (CDC-based method)
Who we work with
- Hotels and resorts
- Tour-operator audits, brand standards, seasonal closures and the guest who falls ill after checking out.
- Hospitals and clinics
- Immunocompromised patients, long pipe runs, warm water everywhere. Water safety plans for accreditation.
- Offices, malls and cooling towers
- Registers, written schemes and checks for cooling towers and the water systems around them.
- Factories and industrial sites
- Process cooling, evaporative condensers and welfare facilities on one site, assessed together.
- Condominiums and serviced apartments
- Roof tanks, stagnant units and shared hot water. A plan juristic persons and managers can run.
Written for the standards your auditors use
There is no single Legionella law in Thailand, so each property is judged by whoever audits it. We map the assessment to the framework that applies to you and say so on the cover.
- Thai Department of Health guidance and the GREEN Health Hotel and 3C Clean Hotel programmes: hot water generated above 60 °C and above 50 °C at the tap, free chlorine of at least 0.2 mg/L checked daily, six-monthly sampling, a water management plan and a responsible officer.
- Tour operators working to the ABTA accommodation guide and the European 15-point plan: a documented prevention plan, a trained responsible person, testing records and seasonal clean-and-disinfect evidence, the items TUI's auditors check.
- International hotel brands running water management programmes to ASHRAE 188 or the WHO water safety plan model, and hospitals preparing for accreditation.
- The UK method itself: BS 8580-1 risk assessment and HSG274 control limits, which set the bar European investigators compare against.
How it works
Site survey
On site with your chief engineer, for as long as the size of the property needs. Every tank, heater, loop, tower, spa and little-used outlet, with temperatures and chlorine measured where the risk sits.
Assessment report
Schematics, a scored risk register and an action plan ranked by urgency and cost. Delivered within five working days.
Written scheme and training
Control limits, check frequencies and logbooks for your team, and a half-day session for the person who will be responsible.
Monitoring and review
Quarterly or six-monthly visits, independent sampling at TEST TECH (ISO 11731:2017), IMC Thai (AS 3896:2017) or a Department of Medical Sciences Regional Medical Sciences Center (CDC-based method), and a re-assessment after refurbishment, closure or an incident.
Who you are dealing with
Envirisk Asia is the Southeast Asian arm of Envirisk, a UK water hygiene company and Legionella Control Association member. Ken carried out and reviewed Legionella risk assessments across the UK for ten years before moving to Bangkok. He does the surveys himself.
Envirisk Asia is a trading name of KLM Hospitality Group Co., Ltd., registered in Thailand.More about us
Get a quote for your property
Tell us the property type, where it is, how many rooms and whether it has cooling towers. We reply with a price and the earliest survey date, usually the same working day.
Had a positive result, or a notification about a guest?
What you do and record in the first 24 hours is what investigators and tour operators will read later. Get in touch now for advice on disinfection, independent resampling and the evidence they will ask for.