Do you actually need this?
Legionella sampling or a legionella assessment: which one does the law require?
Water hygiene companies sell monthly monitoring and quarterly sampling to offices, shops and rented flats. The law requires an assessment and a control scheme. For most small premises, sampling is a cost with no legal basis. Here is the distinction.
What you were told: "You need quarterly legionella testing. It's a legal requirement."
What the law says: You must assess the risk from legionella in your water system and manage it. That's the Health and Safety at Work Act, the COSHH Regulations and Approved Code of Practice L8. The word "sampling" appears in HSE's guidance as something you do when the assessment says control is uncertain. It never appears as a duty.
Two different things
Identify the water system, find where water could stagnate or sit between 20 and 45 degrees, decide the controls (hot water hot, cold water cold, flush unused outlets, inspect any tank), name the responsible person, write it down, keep a log. That's the legal requirement. For a small simple system, HSE says the person managing the premises can often do it.
Taking water samples for laboratory analysis. HSG274 Part 2 says routine sampling is not usually required for hot and cold water systems. It's indicated where temperatures can't be maintained, where the system is complex, where occupants are vulnerable (healthcare, care homes), or where there's a specific concern. Cooling towers and spa pools have their own regimes. For an office, a shop, a salon or a rented flat, it's a decision, not a duty.
Where the money goes
The water hygiene contract: an assessment (fine), then monthly monitoring visits at £30 to £60 each to read two thermometers, plus quarterly sampling at £40 to £80 a sample. For a ten-outlet office that's £600 to £1,500 a year for work the guidance says you can do yourself in ten minutes a month, plus samples the guidance says you don't need.
What to do instead
Get the assessment done, professionally if your system has stored water, tanks, showers or more than a handful of outlets. Then run the control scheme in-house: monthly temperatures at the sentinel outlets, weekly flushing of anything unused, an annual look at the tank if you have one. Write it in a log. Review the assessment every two years or when something changes.
If the assessment specifically recommends sampling, with a reason, follow it. If the contract includes sampling by default, ask what in the assessment justifies it.
What you shouldn’t be sold
- A "legionella certificate". Doesn't exist.
- Routine sampling for low-risk premises. Not in L8, not in HSG274.
- Monthly monitoring visits for a small system. Two thermometers and a log.
- Tank cleaning on a schedule with no inspection finding. The tank is inspected; it's cleaned if it needs it.
- Chemical dosing for an ordinary building. Temperature is the primary control for hot and cold water systems.
Quick answers
- Is legionella testing a legal requirement?
- No. The legal requirement, under the Health and Safety at Work Act, COSHH and Approved Code of Practice L8, is to assess the risk and put controls in place. Sampling is only recommended by HSE where control is uncertain, where occupants are vulnerable, for complex systems, or during an outbreak investigation.
- Do I need a legionella certificate?
- No such document exists in law or HSE guidance. The risk assessment and the log of your monthly checks are the records. A letting agent or contractor asking for a certificate is asking for a form they sell.
This is general information about UK compliance, written for the person paying the bill. It isn’t legal advice. If your situation is unusual, get a professional to look at it.