Five Ways You Void a Hot Water Warranty on the Day You Install It

When a hot water unit fails inside its warranty period and the manufacturer rejects the claim, it's almost never because the unit was defective. It's because something about the installation wasn't compliant, wasn't documented, or didn't meet the manufacturer's specific requirements. Here are the five most common ways it happens.

1. No compliance certificate lodged

Rheem, Rinnai, Bosch, and most other major manufacturers require the installation to be carried out by a licensed plumber and the compliance certificate to be lodged with the relevant authority. Without it, there's no proof the installation met Australian Standards. The warranty requires compliant installation as a condition. No cert — or a cert issued but not lodged — is the first thing a manufacturer checks when a claim is submitted. If the cert number isn't in the file, the claim is already in trouble.

2. No pressure-limiting valve on the cold inlet

AS/NZS 3500.4 requires a pressure-limiting valve (PLV) on the cold water inlet to a hot water unit. The PLV limits mains pressure to a safe level for the unit and downstream pipework. If mains pressure is high and there's no PLV, the unit operates under over-pressure — causing premature failure of the vessel, joints, and fittings. Manufacturers check for this specifically. Missing PLV is an installation defect, and an installation defect voids the warranty.

3. No tempering valve at personal hygiene outlets

AS 4032.2 requires a tempering valve at personal hygiene outlets — showers, baths, basins — in residential installations. The hot water unit stores water at 60°C to prevent legionella growth. The tempering valve blends this down to a safe delivery temperature (maximum 50°C at the outlet). Missing tempering is a compliance failure under AS 4032.2. Several manufacturers flag this specifically in warranty documentation: if the installation wasn't compliant with AS 4032, the warranty doesn't apply.

4. Wrong flue clearances for instantaneous units

AS/NZS 5601.1 specifies minimum clearances from flue terminals to openable windows, doors, air intakes, and adjacent building elements. For instantaneous gas units, these clearances are specific and non-negotiable. A common mistake: mounting a unit near a laundry window that gets opened in summer, or too close to a neighbour's openable window. If the inspector finds it — or the building changes around it — the installation is non-compliant from day one, and the warranty reflects that.

5. Installation in an unapproved location

Most hot water units have specific requirements about where they can be installed: minimum ventilation requirements for enclosed spaces, prohibitions on certain installation orientations, restrictions on proximity to electrical switchboards. Installing a unit in a cupboard without the required ventilation openings, or in a garage without meeting the manufacturer's indoor installation requirements, voids the warranty regardless of how tidy the plumbing looks. The compliance requirement isn't just what you can see — it's what the manual says.