The Legionella duty for the communal water system in a block of flats sits with whoever is in control of that system — usually the freeholder, the residents’ management company, or a right-to-manage company, not the individual leaseholders. Find that party first; everything else follows from it.
That single test, “who is in control of the premises and the water system”, is the one ACoP L8 applies [1]. It rarely lands neatly on one name, which is why blocks get stuck. A freeholder may own the structure, an RMC may run it, a managing agent may do the work, and each leaseholder controls the pipework inside their own front door. Sorting that out is the whole job.
Below is a decision path, then the questions managers actually search for.
A decision tree for the communal duty
Work top to bottom. Stop at the first answer that fits the system you are asking about.
Step 1 — Which system are you asking about?
- Communal cold-water storage tanks, shared risers, a communal calorifier or boosted mains serving multiple flats, communal showers, gym or spa facilities, or landlord taps in plant rooms and bin stores -> this is the communal system. Continue to Step 2.
- The hot and cold water inside a single flat, fed from the demise boundary onward -> the leaseholder or tenant controls that water in use. Jump to Step 5.
Step 2 — Is there an RMC or RTM company running the building?
- Yes, a residents’ management company or right-to-manage company holds the management function under the lease -> that company is the duty holder for the communal system [1]. It is the legal person in control. Continue to Step 3.
- No, the freeholder retains management -> the freeholder is the duty holder. Continue to Step 3.
Step 3 — Has a managing agent been appointed?
- Yes -> the agent carries out the day-to-day work: arranging the risk assessment, monitoring, remedials and records. The legal accountability stays with the RMC, RTM or freeholder who appointed them [2]. Put the split in writing. Continue to Step 4.
- No -> the duty holder from Step 2 does the work itself, or appoints competent people to do it [1]. Continue to Step 4.
Step 4 — Is the duty holder competent to assess and control the risk?
- Yes -> proceed: risk assessment, written scheme of control, monitoring, records, review.
- No (the usual answer) -> appoint a competent person or company to assess and advise, while keeping the duty [1][2]. Competence does not transfer the accountability; it discharges it.
Step 5 — Inside an individual flat.
- The leaseholder, or the tenant if sub-let, controls how that in-flat water is used: running outlets, descaling shower heads, reporting tepid hot water. A private landlord letting a flat also carries the domestic landlord duty for that flat’s system [3]. The communal duty holder still owns everything up to the demise boundary.
The pragmatic call: name the communal duty holder in one sentence, name the appointed competent party in the next, and record both. A block where no one can answer “who holds this” in writing is the block where the assessment never gets done.
Who is the duty holder for the communal water system?
The party in control of the communal system. In a typical leasehold block that is the freeholder, an RMC, or an RTM company, depending on how the building is managed under the lease [1]. The communal system means the shared infrastructure: storage tanks, risers, plant-room calorifiers, boosted cold-water sets and communal outlets. Whoever has the obligation to maintain that infrastructure holds the duty for controlling Legionella in it.
Does appointing a managing agent move the duty off the freeholder or RMC?
No. A managing agent does the work; the accountability stays with the freeholder, RMC or RTM that appointed them [2]. Treat the agent as the competent party who arranges the risk assessment, monitoring and remedials, then check that they actually do. The clean arrangement is a written brief stating who assesses, who reviews, who fixes faults, and who holds the logbook. If something goes wrong, the questions return to the appointing party, not only the agent.
What is the difference between a freeholder, an RMC and an RTM company here?
Ownership versus management. A freeholder owns the building’s structure. A residents’ management company is usually named in the leases and runs the building on the leaseholders’ behalf. A right-to-manage company is one the leaseholders set up to take management from the freeholder. For Legionella, the question is not who owns the freehold but who controls the communal water system day to day [1]. Where an RMC or RTM holds the management function, the communal duty travels with it.
Do individual leaseholders have any Legionella duty?
For the communal system, generally no — they do not control it. For the water inside their own flat, in practice yes: a leaseholder, or their tenant, controls how those outlets are used and is the person who flushes a little-used spare bathroom or descales a furred shower head. A leaseholder who sub-lets becomes a landlord for that flat and picks up the domestic landlord duty for its system [3]. The line is the demise boundary: communal side, the block’s duty holder; flat side, the occupier.
Where does the communal system stop and the flat begin?
At the demised pipework boundary defined in the lease, commonly the point where the supply enters the flat. Up to that point — tanks, risers, communal valves — the communal duty holder is responsible. Beyond it, the leaseholder controls the water in use. The exact boundary varies between leases, so read the demise rather than assume [1]. Where it is genuinely unclear, a competent assessor should map the system and the duty holder should record where responsibility changes hands.
What does the communal duty holder actually have to do?
Assess the risk, control it, and keep records that prove both. In practice that means a Legionella risk assessment of the communal system, a written scheme of control, and monitoring of the controls it identifies [1]. Temperature control is the backbone for most blocks: keeping hot water hot, cold water cold, and water moving [4]. Add tank inspections, attention to dead legs, and a review when anything material changes. None of it needs to be on paper — a digital logbook that timestamps each temperature check and flush makes the “can you prove it” question easy to answer.
Who pays for the communal Legionella risk assessment?
The cost normally falls to the service charge, recovered from leaseholders under their leases. The duty to get the work done still rests with the freeholder, RMC or RTM regardless of funding [1]. Funding and legal accountability are separate questions, and a dispute about the service charge does not pause the duty. Where a block also has commercial units, apportioning shared water-system costs gets more involved — Legionella in mixed-use residential and commercial complexes covers those split-responsibility buildings.
What if a flat is privately let within the block?
Two duties run in parallel. The block’s duty holder remains responsible for the communal system up to the demise; the private landlord of that flat carries the domestic landlord duty for the water system inside it [3]. The friction point is voids: an empty flat with stagnant in-flat pipework draws on the same riser as occupied homes. Landlord responsibilities for Legionella in rental properties sets out the individual-let duty in full.
Where this guidance stops
This is general guidance, not legal advice on your lease. The split between freeholder, RMC, RTM and leaseholder is ultimately fixed by the lease and management structure of your specific building, and those documents override any rule of thumb here. A competent person should carry out the site-specific risk assessment, map the system, and confirm where the communal duty ends and the flat begins. Any temperatures, intervals or limits you act on should come from that assessment, not a generic figure [1][4].
If you only do one thing
Today, write one sentence: “The duty holder for the communal water system at this block is ___, and the appointed competent party is ___.” If you cannot complete it from the lease and the management agreement, that gap is your first job — close it before the next risk assessment is due. Then start a single shared logbook for the communal system so the assessment, monitoring and faults all live in one place rather than across a managing agent’s inbox and a contractor’s clipboard.
Sources
[1] HSE, “Legionnaires’ disease. The control of legionella bacteria in water systems - ACoP and guidance (L8)”. https://www.hse.gov.uk/pubns/books/l8.htm [2] HSE, “Legionnaires’ disease - what you must do”. https://www.hse.gov.uk/legionnaires/what-you-must-do/index.htm [3] HSE, “Legionella and landlords’ responsibilities”. https://www.hse.gov.uk/legionnaires/legionella-landlords-responsibilities.htm [4] HSE, “Hot and cold water systems”. https://www.hse.gov.uk/legionnaires/hot-and-cold.htm