Do you actually need this?
Required by lawLegionella sampling or a legionella assessment: which one does the law require?
The law asks for a legionella risk assessment and a control scheme. HSE only calls for sampling in some cases. We think an assessment without water samples tells you very little. Here is the difference and what we advise.
What you were told: "You need a legionella certificate. It's a legal requirement."
What the law says: You must assess the risk from legionella in your water system and control it. That is the Health and Safety at Work Act and the COSHH Regulations and Approved Code of Practice L8. There is no such thing as a legionella certificate.
Two different things
The assessment looks at your water system. It finds where water could sit still or sit between 20 and 45 degrees. It sets the controls. Hot water hot and cold water cold. Little used outlets flushed. Tanks inspected. It names the person responsible. All of it is written down and the checks go in a log. That is the legal requirement.
Water samples sent to a laboratory. HSE does not make sampling a duty for ordinary hot and cold water systems. It says sampling is for certain cases. Those include systems treated with biocide and systems where temperatures are not being held. They also include places with vulnerable people and any suspected case or outbreak.
What HSE says
Microbiological monitoring of domestic hot and cold water supplied from the mains is not usually required, unless the risk assessment or monitoring indicates there is a problem.
That is the regulator's position. Here is mine.
Why I like sampling
I like sampling. It is the best way to find out whether there are bacteria in your water. Not just legionella either.
An assessment tells you what your system looks like. A sample tells you what is in it. They are not the same thing. Water sits in tanks and in dead legs and in showers nobody has run for weeks. A drawing will never show you a local build up of bacteria. A bottle sent to a lab will.
A laboratory does more than look for legionella. It can give a total viable count of all the bacteria in the water. It can test for coliforms and E. coli. That tells you whether the water your staff and customers drink and wash in is as clean as the water that came in from the mains.
So in my view an assessment without samples is close to useless. A sample costs about £55. Hot and cold together is about £140. That is cheap for knowing. I would sample when the assessment is done and then as often as your water hygiene engineer recommends.
Who should run the control scheme
HSE says a trained person on site can carry out simple checks. That part is true. The monthly temperature checks at the sentinel outlets are simple. So is weekly flushing of taps and showers nobody uses. A trained person on site can do those and write them in the log.
Most premises are not that simple though. Look at what you actually have. Thermostatic mixing valves on the taps or showers. An expansion vessel on the hot water. A stored hot water cylinder or a calorifier. A cold water tank in the loft. Showers.
If you have any of those then most of your control scheme is engineer work. The TMVs need servicing. The expansion vessel needs flushing. The tank needs inspecting and cleaning. The calorifier needs draining and the showerheads need descaling. Those are jobs for a water hygiene engineer. They are not jobs for the person who reads the thermometer.
Getting it wrong matters. A TMV that is not serviced can let water through too hot or let bacteria grow behind it. An expansion vessel that is never flushed can hold stagnant water right next to your hot supply.
What to do
Get the assessment done by someone competent. Use a Legionella Control Association member if you have tanks or TMVs or showers. Take water samples at the same time. Have a trained person on site take the monthly temperatures and keep the log. Then have a water hygiene engineer do the TMVs and the vessel and the tank on the schedule the assessment sets.
What you shouldn’t be sold
- A "legionella certificate". It does not exist.
- Chemical dosing for an ordinary building. Temperature is the main control for hot and cold water systems.
- Tank cleaning on a fixed schedule with no inspection finding. The tank is inspected. It is cleaned if it needs it.
- Monthly visits just to read two thermometers on a simple system. If you have no TMVs and no tank and no stored hot water a trained person on site can do this.
Quick answers
- Is legionella testing a legal requirement?
- No. The legal requirement is to assess the risk and put controls in place. That comes from the Health and Safety at Work Act and COSHH and the Approved Code of Practice L8. HSE only recommends sampling in certain cases. Our advice is to sample anyway because it is the only way to know what is in the water.
- What does a water sample test for?
- A laboratory can test for legionella. It can also give a total viable count of all bacteria and test for coliforms and E. coli. Together they tell you whether the water in your building is as clean as the water that came in from the mains. A sample costs about £70.
- Can I run the legionella control scheme myself?
- Only the simplest parts. A trained person on site can take the monthly temperatures and flush little used outlets. Most premises also have TMVs or an expansion vessel or a stored hot water cylinder. Servicing those is a job for a water hygiene engineer.
- Do I need a legionella certificate?
- No such document exists in law or HSE guidance. The risk assessment and the log of your checks are the records. A letting agent or contractor asking for a certificate is asking for a form they sell.
General information, written for the person paying the bill. Opinion is labelled as opinion. Not legal advice. See our editorial standards.