Domestic Gas Hot Water System Replacement SWMS

Domestic gas hot water system replacement covers the removal of an existing gas water heater and the installation and commissioning of a replacement gas water heater at a domestic property — the disconnection and removal of the old unit, the gas and water connections of the new unit, and the commissioning that proves the installation is safe. It is everyday but high-consequence gasfitting work: the gas connection carries the risk of a leak, fire or carbon monoxide, and the heated water carries the scalding and Legionella risks common to all heated water. This document is written on the basis that domestic gas hot water replacement is carried out by a licensed gasfitter, with the gas installation and commissioning to the gas standard and the heated water to the heated water standard.

Domestic gas hot water replacement is carried out to AS/NZS 5601.1:2022 Gas installations Part 1 for the gas installation, connection, leak testing and commissioning of the gas water heater, and to AS/NZS 3500.4 for the heated water service, temperature control and relief. Delivered water to sanitary fixtures used for personal hygiene must be temperature-limited to prevent scalding, the system must control Legionella, and the gas appliance must be commissioned with correct combustion. This document coordinates the gas-standard, heated-water, scalding, Legionella and commissioning controls so the replacement is installed and left safe.

Hazards identified

9 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Administrative: isolate the gas and water and make safe before removing the old unit, and install the replacement gas water heater to AS/NZS 5601.1:2022 and the heated water service to AS/NZS 3500.4.
2. 2Engineering: provide and confirm adequate ventilation and flueing for the appliance, and install or verify the flue so combustion products are safely discharged.
3. 3Engineering: fit a tempering or thermostatic mixing valve so delivered water to sanitary fixtures used for personal hygiene is limited to the required maximum to prevent scalding, while the system controls Legionella.
4. 4Engineering: fit and confirm the pressure and temperature relief valve and pipe the relief discharge to a safe, visible disposal point so hot discharge cannot scald.
5. 5Administrative: leak test and pressure test the gas connection before placing the appliance in service, and commission the appliance with combustion testing and a carbon monoxide check.
6. 6Administrative: control all ignition sources during the work — no naked flames, no electrical switching, and control of static — and use a gas detector or approved leak-detection fluid rather than a flame for leak finding.
7. 7Engineering: isolate, depressurise and allow the old unit to cool before removal, and use correct manual-handling technique or aids for the heavy units.
8. 8Administrative: ensure the work is carried out and certified by an appropriately licensed gasfitter or plumber under the relevant state or territory gasfitting and plumbing licensing scheme, with a compliance certificate issued where required.
9. 9Administrative: all workers must hold a valid White Card (General Construction Induction Training, CPCCWHS1001) before entering any construction workplace, with the gasfitting, plumbing and any confined space competencies and licences required for the work.
10. 10Administrative: conduct a daily pre-start toolbox talk covering the day's work, identified hazards, isolations, required PPE and emergency procedures, and record attendance in the consultation section.
11. 11Administrative: consult workers and any health and safety representatives on the work and its risks, record the consultation, and keep this document available at the workplace.
12. 12PPE: eye protection to AS/NZS 1337.1, hearing protection where required, gloves appropriate to the task, and Class I or Class II safety footwear with protective toecap to AS/NZS 2210.3.
13. 13Administrative: review and update this SWMS whenever the work scope changes, after any incident or near miss, when a worker or health and safety representative raises a concern, when new hazards are identified, or at minimum every 12 months.

Applicable Codes of Practice

Worked example

A licensed gasfitter is engaged to replace a failed gas storage water heater at a home with a new gas water heater. The gas and water are isolated and made safe, and the old unit is isolated, depressurised and allowed to cool before removal, handled with correct technique. The replacement is installed to AS/NZS 5601.1:2022 for the gas and AS/NZS 3500.4 for the heated water service. Ventilation and flueing are provided and confirmed so combustion products are safely discharged. A tempering valve is fitted so delivered water to the bathroom fixtures is limited to the required maximum to prevent scalding, while the system controls Legionella, and the pressure and temperature relief valve is fitted with the discharge piped to a safe, visible point. The gas connection is leak tested and pressure tested, and the appliance commissioned with combustion testing and a carbon monoxide check, with ignition sources controlled and a gas detector used for leak finding. The gasfitter confirms the system is safe, issues the compliance certificate, and retains the records.

Related legislation

• Model Work Health and Safety Act — primary duty of care; the duty to consult workers; the reckless-conduct offence; and notifiable-incident provisions, as enacted in each jurisdiction.
• Model Work Health and Safety Regulations — Section 291 high risk construction work and the SWMS preparation and review duties, and the confined space, excavation and pressurised-gas provisions where applicable, as enacted in each jurisdiction.
• The gas installation standard AS/NZS 5601.1:2022, the LP Gas storage standard AS/NZS 1596, the medical gas standard AS 2896, and the relevant plumbing and drainage standards AS/NZS 3500, are called up by the state and territory gas and plumbing safety legislation, together with the Type B and medical gas certification requirements and the gas network operator's requirements where applicable.
• Gasfitting and plumbing work is licensed under each state and territory's gasfitting and plumbing licensing scheme, with Type B authorisation and medical gas certification required for that work, and compliance certification required for notifiable work.
• Victoria operates under the Occupational Health and Safety Act 2004 and the Occupational Health and Safety Regulations 2017, with the high risk construction work, confined space and excavation provisions applying in place of the model instruments.

Frequently asked questions