Flue Terminal Clearance on a Tight Boundary
A licensed gasfitter is replacing a 20-year-old internal instantaneous water heater in a two-storey home. The new unit is a fan-assisted Type B appliance rated at 26 MJ/h, and the manufacturer's instructions specify a minimum flue terminal clearance of 300 mm from any openable window and 500 mm from a boundary. The only practical flue position puts the terminal 380 mm below the top of an openable first-floor window and 420 mm horizontally from the neighbouring property boundary. The homeowner is impatient and says the old unit was in the same spot. The gasfitter notes the old appliance was a natural-draught unit with a different terminal design and that the window was replaced six months ago.
1. How should the gasfitter decide whether the proposed flue position is acceptable?
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The decision is not "the old one was there, so it's fine". The old appliance's terminal was a different design, and the window is new, so the previous installation tells you nothing about compliance of the new unit.
The gasfitter must apply the most stringent of: the manufacturer's instructions for the new appliance (300 mm window, 500 mm boundary), and the applicable Australian Standard requirements for flue terminal location. Manufacturer's instructions are mandatory under gas regulations, not advisory. If the standard requires a greater clearance than the instructions, the greater figure governs.
Here the 380 mm window clearance satisfies the 300 mm instruction, but the 420 mm boundary clearance fails the 500 mm instruction by 80 mm. Unless the standard permits a lesser distance in this specific configuration (for example, a boundary with no habitable structure), the position is non-compliant.
The correct action is to relocate the terminal, use an approved extension or cowl that restores clearances, or select a different appliance. Documenting why the original position is unsuitable protects the gasfitter later.
2. The homeowner asks the gasfitter to install it anyway and says they will sign a waiver. What is the appropriate response?
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A waiver from a consumer cannot displace statutory obligations. Gasfitting work must comply with the gas regulations, the relevant standards and the manufacturer's instructions; a homeowner cannot contract out of those duties, and a signature does not convert non-compliant work into compliant work.
Installing a flue terminal too close to a boundary creates a foreseeable risk of combustion products entering a neighbour's property, and the gasfitter would bear responsibility. The gasfitter should:
- Decline to install in the non-compliant position, explaining plainly that the waiver has no legal effect.
- Offer compliant alternatives: relocate the terminal, fit an approved terminal extension, or select an appliance that suits the available space.
- Record the advice given and the options offered.
- If the customer still insists, the gasfitter may decline the job. Walking away is the correct commercial and professional outcome.
The gasfitter's licence, insurance and duty of care all depend on refusing work that cannot be done lawfully and safely.