An asset register is the spine of your Legionella file. It is the single list of every part of the water system that needs a control, a check, or an owner — every outlet, calorifier, cold water storage tank, thermostatic mixing valve and pump. Get it right and the risk assessment, monitoring schedule and written scheme all hang off it. Get it wrong and you are monitoring a system you cannot fully see.
This is a template you can build today, in a spreadsheet, before anyone buys software. Below are the columns to capture, what to record for each type of asset, and the rows people quietly skip.
Why the register comes first
The risk assessment describes risk. The written scheme says what you will do about it. But both assume you already know what you are managing. HSG274 frames control as something applied to identified assets and outlets — you cannot write a scheme for a calorifier you have not logged, or set a flushing regime for a tap nobody recorded [1].
The register is also where ownership gets pinned down. An unassigned shower in a rarely-used changing room is not a paperwork problem; it is a stagnation risk with no name against it. The register is where that asset stops being invisible.
L8 expects duty holders to keep records that identify the system and the precautions taken against Legionella [2]. A clean, current asset register is the most basic form of that evidence.
The field checklist: columns to capture
Build your register so every row carries enough to act on without walking back to the plant room. Capture these for each asset:
- Asset ID — a unique, durable reference (e.g. CWS-01, TMV-204, OUT-G12). Label the physical asset to match.
- Asset type — outlet, calorifier, CWST, TMV, pump, expansion vessel, water softener, point-of-use heater.
- Location — building, floor, room, and a plain-English landmark (“under sink, accessible WC”).
- Description / make-model — enough to identify it on sight and order parts.
- Served by / feeds — which system or zone, hot or cold, and what is downstream.
- Sentinel flag — is this a sentinel outlet (nearest/furthest on a loop) used to represent the system? [3]
- Monitoring tasks — temperature check, flush, descale, inspection, sample point — and the frequency your risk assessment sets.
- Usage / frequency of use — daily, weekly, infrequent. This drives flushing.
- Risk notes — dead leg, blended outlet, vulnerable user group, hard-to-reach.
- Responsible person — who owns the check.
- Status / date added / last reviewed — in service, isolated, removed, capped.
Verb-first and recordable beats vague. “Flush weekly, record temperature” is a task. “Monitor” is not.
What to record by asset type
Outlets (taps, showers, drinking points). Log every wet point, not just the obvious ones. Mark sentinel outlets clearly — these are the points used to represent the wider system for temperature monitoring [3]. Flag blended outlets fed via a TMV, because the temperature you read there is not the system temperature. Note any outlet used less than weekly; low use is where stagnation hides.
Calorifiers and water heaters. Record capacity, location, the drain-off point, and whether there is a working flow/return. Hot water is expected to be stored hot and distributed hot, with cold kept cold; your register should make it obvious where each calorifier sits in that distribution so checks land in the right place [4].
Cold water storage tanks (CWST). Capacity, material, lid and insect-screen condition, and overflow arrangement. A tank with a poor lid is a contamination route, so the register should prompt the inspection rather than rely on memory.
Thermostatic mixing valves (TMVs). These deserve their own discipline. Record the valve, the outlet it serves, and the servicing/disinfection interval. TMVs blend to a safe delivery temperature, which means they create a section of pipe between the valve and the spout sitting in the bacterial growth range — exactly the spot you need on the register, not lost inside a generic “shower” row.
Plant and ancillaries. Pumps, expansion vessels, water softeners, filters, point-of-use heaters, and any infrequently-used or dead leg. The pragmatic call: if it holds water or moves it, it earns a row.
How to use and record it
The register is a living document, not a one-off survey output. Three habits keep it honest:
- Reconcile against the schematic. Every asset on the drawing should appear as a row, and every row should map to the drawing. Mismatches are usually where unrecorded assets live — see Using water system schematics and asset registers in risk assessments.
- Drive monitoring from it. Each asset’s tasks and frequencies feed your monitoring schedule. Temperature checks and their frequency follow the risk assessment rather than a fixed calendar, so the register has to carry that detail per asset [5].
- Update on change. New tap, capped dead leg, decommissioned heater — the register changes the same day, with a date and a name.
A register is an inventory, not a control. Listing a calorifier does not make it safe; it only ensures the check that does happen. Treat the register as the prompt sheet for action, and have a competent person fold it into a site-specific risk assessment that decides the actual temperatures, frequencies and limits for your building. This article is general guidance, not a substitute for that assessment.
The rows people skip
The gaps are predictable. Irrigation and outside taps. Eye-wash stations and emergency showers. The kitchen pot-wash and the cleaner’s bucket-fill point. Point-of-use water heaters and instant boilers. The flexible hose feeding a vending machine. Capped dead legs that someone left in place “for now.” None feel like a Legionella asset until they are the one outlet nobody flushed.
Spreadsheet or digital register
A spreadsheet is a perfectly legitimate place to start, and starting beats waiting. Where a flat sheet strains is at the join between the register and everything it should drive: a column saying “flush weekly” does not chase the person who missed last Tuesday, does not timestamp who checked what, and quietly drifts out of date as assets change.
A digital asset register in L8log keeps each asset’s tasks, frequencies and history attached to the asset itself, schedules the checks, and produces the audit-ready record automatically. If your file already lives in a spreadsheet, the genuinely useful next step is to export it cleanly — one row per asset, consistent IDs — so it imports straight in. Setting that foundation up well is covered in Setting up a digital Legionella logbook, and tying it into wider FM workflows in Integrating Legionella records with facility management systems.
FAQ
What makes a good asset ID?
A unique, short, durable reference that you can physically label on the asset and that will not change if the building is re-furbished — a type prefix plus a number works well (TMV-204, CWS-01). Avoid IDs based on the room name alone, because rooms get renamed and reassigned.
Do I really need every outlet on the register, or just sentinels?
Every wet point belongs on the register; sentinels are a subset you flag for representative temperature monitoring [3]. A register that lists only sentinels hides the infrequently-used outlets where stagnation tends to develop, which defeats the point of having one.
How often should the register be reviewed?
Review it whenever the system changes and at the review points your risk assessment sets — and at minimum alongside the periodic risk assessment review. Any new, removed, capped or isolated asset should be updated on the day the work happens, not at the next annual sweep.
Sources
[1] HSE, “Legionnaires’ disease: Technical guidance (HSG274)”. https://www.hse.gov.uk/pubns/books/hsg274.htm [2] HSE, “Legionnaires’ disease. The control of legionella bacteria in water systems - ACoP and guidance (L8)”. https://www.hse.gov.uk/pubns/books/l8.htm [3] HSE, “Testing and monitoring your water system for legionella”. https://www.hse.gov.uk/legionnaires/testing-monitoring-water-system.htm [4] HSE, “Hot and cold water systems”. https://www.hse.gov.uk/legionnaires/hot-and-cold.htm [5] HSE, “Legionnaires’ disease - what you must do”. https://www.hse.gov.uk/legionnaires/what-you-must-do/index.htm