Skip to main content
PM Assist
Cooling Maintenance

Water-Cooled Chiller Maintenance Checklist

A maintenance checklist for water-cooled chillers — condenser tube fouling and approach temperature, brushing and eddy current testing, condenser water flow and treatment chemistry, and the legionella duties that come with an evaporative cooling system.

Generate a custom checklist
Try PM Assist freeTry the live demo

Also available as editable Excel and Word — with asset, sign-off and findings columns.

What is a water-cooled chiller maintenance checklist?

A water-cooled chiller maintenance checklist is a structured list of the 17 preventive maintenance tasks — covering visual, functional, cleaning, safety and record-keeping checks — that keep a water-cooled chiller running safely and reliably. It groups routine checks by frequency, from daily inspections to annual servicing, so FM teams and building engineers can plan and evidence preventive maintenance.

Core water-cooled chiller checks

  • Inspect condenser tubes internally for scale, biofilm, silt and mud deposits at the tube ends
  • Record condenser approach temperature
  • Brush-clean condenser tubes with correctly sized nylon or brass brushes appropriate to the tube material
  • Confirm cooling tower cleaning and disinfection is in date and recorded, and that the tower condition supports the chiller's design condenser water temperature
  • Review microbiological monitoring results including dip slide or total viable count sampling and legionella sampling as set out in the control scheme

What is a water-cooled chiller?

A water-cooled chiller rejects heat into a condenser water circuit rather than to ambient air. That circuit carries the heat to a cooling tower or evaporative condenser, where it is dissipated largely through evaporation. Because evaporative heat rejection reaches a lower condensing temperature than an air-cooled machine can, water-cooled plant is substantially more efficient at full load, which is why it remains the choice for large commercial buildings, hospitals and data centres.

The efficiency comes at the cost of a whole additional system to maintain. A water-cooled installation adds a cooling tower, condenser water pumps, strainers, and a water treatment regime — and each of those has a direct effect on chiller performance. The chiller cannot be maintained in isolation from the circuit it rejects heat into, and a great many apparent chiller faults are actually condenser water faults.

It also brings a statutory dimension that air-cooled plant does not have. A cooling tower is an evaporative system creating an aerosol, so it falls within the legionella control duties set out in the HSE's Approved Code of Practice L8 and the detailed guidance in HSG274 Part 1. Cooling towers and evaporative condensers must also be notified to the local authority. Those duties sit with the operator regardless of who holds the maintenance contract, and the water treatment regime that satisfies them is the same regime that keeps the condenser tubes clean.

This checklist is one of 34 in our HVAC maintenance checklists, covering air handling units, fan coils, chillers, VRF, ductwork and extract systems — filters, coils, refrigerant and damper checks.

Typical Water-Cooled Chiller maintenance checklist

A practical starting point for planned preventive maintenance. Always refer to the manufacturer's O&M manual and site-specific requirements.

Water-Cooled Chiller maintenance checklist showing tasks such as cooling tower checks required and log condenser and evaporator approach, each with its service frequency
A preview of the Water-Cooled Chiller maintenance checklist — the full 17-task routine, service frequencies and safety notes are below, free to download as a PDF.

Visual Checks

  • Inspect condenser tubes internally for scale, biofilm, silt and mud deposits at the tube ends
  • Check tube ends for erosion, grooving and inlet-end wear caused by excessive water velocity or entrained solids
  • Inspect condenser waterboxes, end covers, gaskets and any sacrificial anodes for corrosion and wastage

Functional Checks

  • Record condenser approach temperature — the difference between leaving condenser water temperature and saturated condensing temperature — and trend it against commissioning data
  • Record evaporator approach temperature and chilled water ΔT against design
  • Arrange eddy current testing of the condenser tube bundle to detect wall thinning and pitting before a tube fails
  • Verify condenser water flow rate against design and confirm condenser water pump duty and standby operation
  • Check water treatment chemistry — conductivity, pH, inhibitor residual and biocide levels against the written control scheme
  • Record refrigerant suction and discharge pressures and verify superheat and subcooling against the manufacturer's target range
  • Check compressor oil level, colour and acidity, and take an oil sample for analysis on large machines

Cleaning & Housekeeping

  • Brush-clean condenser tubes with correctly sized nylon or brass brushes appropriate to the tube material — never steel brushes in copper tubes
  • Clean condenser water strainers and check the differential pressure across them

Safety Checks

  • Confirm cooling tower cleaning and disinfection is in date and recorded, and that the tower condition supports the chiller's design condenser water temperature
  • Test safety controls including high pressure cutout, low pressure cutout, condenser and chilled water flow switches and the freeze stat

Record Keeping

  • Review microbiological monitoring results including dip slide or total viable count sampling and legionella sampling as set out in the control scheme
  • Confirm the cooling tower or evaporative condenser is notified to the local authority and that the notification details remain current
  • Update the F-Gas logbook with charge, any top-up, leak test result and the engineer's certificate number

Download the free Water-Cooled Chiller maintenance checklist PDF

Get all 17 tasks as a printable PDF — free, no signup needed. Keep a copy in the plant room, attach it to work orders, or share it with your maintenance contractor.

Generate a custom checklist
Try PM Assist freeTry the live demo
PDF

The PDF is free and needs nothing. The Excel and Word versions add asset details, sign-off and findings columns so you can record the work as you do it — we ask for an email address for those.

Typical maintenance frequency

Suggested intervals for water-cooled chiller maintenance. Actual frequencies should follow manufacturer guidance and site-specific risk assessments.

Weekly

  • •Cooling tower checks required by the written control scheme, including visual condition and any automatic dosing confirmation

Monthly

  • •Log condenser and evaporator approach temperatures, pressures and compressor currents
  • •Water treatment chemistry checks against the control scheme parameters
  • •Check condenser water strainer differential and clean where required

Quarterly

  • •Full performance check under load with approach temperatures compared against commissioning data
  • •Test safety controls and flow switches
  • •Review microbiological monitoring trends and act on any adverse results

Every 6 Months

  • •Cooling tower clean and disinfect in line with HSG274 Part 1 and the site's written control scheme
  • •Condenser tube inspection at the tube ends and waterbox condition check
  • •F-Gas leak check where the charge places the unit on a six-monthly interval

Annually

  • •Comprehensive service including condenser tube brush cleaning
  • •Eddy current test of the condenser tube bundle
  • •Compressor oil and filter change with oil analysis
  • •Electrical thermography of panel, starter and motor terminations
  • •Review of the legionella risk assessment and written control scheme
  • •F-Gas leak check and logbook update at the interval set by the CO₂e charge

Common faults and issues

Issues to be aware of when maintaining water-cooled chiller equipment.

Condenser tube fouling — scale, biofilm or silt raising approach temperature, condensing pressure and compressor power draw well before any fault is indicated
Rising condenser approach temperature treated as a chiller problem when it is a water treatment problem
Tube end erosion from excessive condenser water velocity or entrained sand and grit, eventually thinning tube walls to failure
Water treatment regime lapsing — dosing pump failure, empty chemical drums or an out-of-date control scheme allowing scale and biofilm to establish
Cooling tower fill fouling or scaling, raising condenser water temperature and derating the chiller regardless of the chiller's own condition
Condenser water strainer blockage reducing flow, sometimes to the point of a flow switch trip mistaken for a pump fault
Legionella control failures — sampling gaps, missed cleans, or a written control scheme that no longer matches the installed system
Corrosion of waterboxes, end covers and tube sheets where sacrificial anodes have wasted away unreplaced
Refrigerant leaks at the condenser tube sheet, which can pass refrigerant into the condenser water circuit and are easily missed

Safety and compliance notes

Key safety considerations for water-cooled chiller maintenance. This is general guidance only — always follow OEM instructions, statutory requirements, and your organisation's safe systems of work.

All refrigerant work must be carried out by an F-Gas certified engineer — this is a legal requirement
Cooling towers create an aerosol and carry a legionella risk: work on the tower or condenser water circuit must follow the site's legionella risk assessment and written control scheme under HSE ACoP L8 and HSG274 Part 1
Cooling towers and evaporative condensers must be notified to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992
Entry into a cooling tower may be a confined space — assess before entry, never as an afterthought, and follow the site permit system
Water treatment chemicals include biocides and acids: handle to the COSHH assessment, use the specified PPE, and never mix products
Large chillers operate at 400V and above with high starting currents — observe safe isolation, lock-off and prove-dead procedures
Condenser waterboxes may be under pressure and heavy — depressurise and drain before removing end covers, and plan the lift
Always refer to the manufacturer's O&M manual for tube cleaning methods, brush materials and torque figures for waterbox covers

Reference standards and frameworks

United Kingdom
SFG20, CIBSE Guide M, and the UK F-Gas Regulations for refrigerant plant
North America
ASHRAE/ACCA Standard 180, plus EPA Section 608 refrigerant handling rules
Middle East
Dubai Municipality's Green Building Regulations require commissioning to CIBSE Commissioning Code R (refrigeration systems)

Frameworks commonly referenced when planning water-cooled chiller maintenance programmes. Always confirm the requirements that apply to your site and jurisdiction.

How PM Assist helps

Managing Water-Cooled Chiller documentation with PM Assist

PM Assist helps FM and building operations teams search their O&M manuals and building drawings in seconds. Upload your water-cooled chiller documentation and ask questions like “What is the rated cooling capacity?” or “When was the last F-Gas leak check?” — and get source-cited answers instantly.

The checklist tells you what to check. The manual tells you the numbers.

Ask a water-cooled chiller manual a question and get the answer back with the page it came from. No signup, and you can drop in your own PDF instead of the sample.

“What is the rated cooling capacity?”

Runs against a sample chiller manual so you can see the shape of the answer — then try it on one of yours.

Take this checklist with you

Download the branded PDF, generate a custom version for your asset, or run AI search across all your building documentation.

Instant download either way — the email is optional. One short email a month, unsubscribe anytime. See our privacy policy.

Generate a custom checklist
Try PM Assist freeTry the live demo

Related free tools

Chiller Diagnostic & Refrigerant CalculatorF-Gas CO₂e CalculatorHVAC Fault DiagnosisMaintenance Checklist GeneratorAll free tools

Related maintenance checklists

Chiller maintenance checklist

Cooling · 18 tasks

Air-Cooled Chiller maintenance checklist

Cooling · 16 tasks

Process Chiller maintenance checklist

Cooling · 16 tasks

Cooling Tower maintenance checklist

Cooling · 12 tasks

Condenser maintenance checklist

Cooling · 10 tasks

Water Treatment Unit maintenance checklist

Water Systems · 10 tasks

Chemical Dosing Pot maintenance checklist

Water Systems · 8 tasks

Pump maintenance checklist

Pumps & Pressurisation · 12 tasks

All HVAC maintenance checklistsView all maintenance checklists

Further reading on water-cooled chiller maintenance

Reactive vs Planned Maintenance Explained·Why Building Engineers Waste Hours Searching Documentation·How AI Can Transform Facilities Management·All articles

Compliance topics for water-cooled chiller maintenance

F-Gas Regulations Explained·SFG20 Explained: The Standard for Building Maintenance·Planned Preventive Maintenance (PPM) Explained·TM44 Air Conditioning Inspections Explained·All topics

Related guides

Find Equipment Specifications Across Building Documents·Find Maintenance Schedules in O&M Manuals·Search Building System & Maintenance Records with AI·Planned Preventive Maintenance Documentation·All guides·UK facilities management statistics

Refrigerants used in water-cooled chiller

GWP, the charge in kg at which leak checks start, and the Great Britain and Northern Ireland figures side by side.

R-134a GWP·R-513A GWP

Compliance & CAFM

Run water-cooled chiller maintenance in PM Assist

This checklist is also a planned maintenance programme in PM Assist, included in every paid plan alongside the compliance register and mobile inspections.

  • Add a water-cooled chiller to a building's asset register and this maintenance programme is created for you, with each task on its frequency in the planner.
  • Air Conditioning Inspection (TM44) and F-Gas Leak Check are tracked on the compliance register, with the date last done, the date next due and the certificate.
  • Contractors can be given a login to see their jobs and upload certificates.
See the compliance and PPM softwareCompare plans

Frequently asked questions

What is condenser approach temperature and why does it matter?
Condenser approach is the difference between the saturated condensing temperature of the refrigerant and the temperature of the water leaving the condenser. It is the single most useful indicator of condenser tube fouling available without opening the machine. Clean tubes transfer heat efficiently and the approach stays close to its commissioned value; as scale or biofilm builds, heat transfer worsens and the approach widens. Trending approach at every visit gives weeks or months of warning before fouling shows up as high head pressure or a high-pressure trip, and it distinguishes a fouling problem from a refrigerant charge problem, which the pressures alone often will not.
How often should condenser tubes be cleaned on a water-cooled chiller?
Annual brush cleaning as part of the comprehensive service is the usual baseline, but the honest answer is that the water treatment regime and the approach temperature trend should set the interval, not the calendar. A well-treated closed condenser circuit on a clean site may hold its approach for years; an open circuit with poor treatment, a fouled tower or high make-up water hardness can need attention within a season. If approach temperature has widened noticeably since commissioning, the tubes need cleaning regardless of when they were last done.
What is eddy current testing and does my chiller need it?
Eddy current testing passes a probe through each condenser tube to detect wall thinning, pitting and cracking that a visual inspection of the tube ends cannot see. It produces a condition report for the bundle rather than a pass or fail for the machine, which lets you plan tube plugging or a re-tube before a tube fails in service. A failed condenser tube floods the refrigerant circuit with water and typically means a major overhaul, so on any significant water-cooled chiller — particularly one over ten years old, or one with a history of poor water treatment or tube end erosion — periodic eddy current testing is inexpensive insurance rather than an optional extra.
What legionella duties come with a water-cooled chiller?
The chiller itself does not create the risk; the cooling tower or evaporative condenser it rejects heat into does, because it generates an aerosol that can carry legionella bacteria. That brings the installation within the HSE's Approved Code of Practice L8, with the practical detail set out in HSG274 Part 1. In outline the operator must have a suitable and sufficient risk assessment, appoint a responsible person, implement a written scheme of control, monitor and record water treatment and microbiological results, and clean and disinfect the tower — HSG274 Part 1 recommends at least twice a year. Cooling towers and evaporative condensers must additionally be notified to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992. These duties sit with the operator whoever holds the maintenance contract.
Why is my water-cooled chiller losing efficiency when the chiller itself tests fine?
Because on a water-cooled installation most efficiency lives in the condenser water circuit rather than in the machine. A fouled cooling tower fill, a tower fan running at reduced speed, low condenser water flow from a blocked strainer or worn pump, scale in the condenser tubes, or a treatment regime that has quietly lapsed will each raise condensing temperature and increase compressor power draw for the same cooling output. The chiller will test as mechanically sound throughout. Start with approach temperatures and condenser water flow before investigating the refrigerant circuit.
Are water-cooled chillers more efficient than air-cooled?
At full load, generally yes — evaporative heat rejection reaches a lower condensing temperature than dry air-cooled rejection can, and lower condensing temperature means less compressor work per unit of cooling. The comparison is less clear cut in practice. Water-cooled efficiency depends on the tower, pumps and treatment all being maintained, and the auxiliary power of condenser water pumps and tower fans has to be counted against the chiller's own saving. A neglected water-cooled installation can easily perform worse than a well-maintained air-cooled one, and it carries the legionella duties as well.
What water treatment does a condenser water circuit need?
An open evaporative circuit concentrates dissolved solids as water evaporates, so it needs a treatment regime covering scale and corrosion inhibition, biocide dosing, and control of concentration through bleed-off, together with monitoring of conductivity, pH, inhibitor residual and microbiological activity. The specifics belong in the site's written scheme of control, drawn up against the legionella risk assessment and the make-up water quality. The point worth making to any FM team is that this is not a separate compliance exercise running alongside the chiller service — the same regime that controls legionella risk is what keeps the condenser tubes clean and the chiller efficient.
What superheat and subcooling should a water-cooled chiller run at?
As with any refrigeration machine, the manufacturer's O&M manual sets the targets and they vary by refrigerant and compressor type. The useful discipline is comparing against your own commissioning figures at every service. On a water-cooled machine, interpret them alongside the approach temperatures: high subcooling with a widening condenser approach points to fouling rather than overcharge, whereas high subcooling with a normal approach is more likely a charge issue. Reading the refrigerant side without the waterside on this type of plant leads to a lot of unnecessary refrigerant work.

Manage your building documentation with AI

PM Assist gives FM teams instant access to O&M manuals, drawings, and maintenance knowledge — all searchable with AI.

  • Upload and organise building documentation
  • AI-powered search across all your manuals
  • Source-cited answers for maintenance queries
  • Team collaboration and access control
  • No credit card required to start
Generate a custom checklist
Try PM Assist freeTry the live demo