Perth conditions that shape the choice
Gas arrives on ATCO's network
The gas distribution systems serving the Perth greater metropolitan area, Mandurah included, are owned by ATCO Gas Australia. Work on a gas water heater's gas side needs a WA gasfitting licence.
Within the hardness guideline
Water Corporation says Perth's metropolitan supply meets the national hardness guideline, which draws the line at 200 mg/L. Its tip for hot water systems is still to release the pressure valves for a few seconds each month, to stop scale building up.
Mild winter nights
Perth Airport and Perth Metro both average a July minimum of 8.1°C, and Perth Airport has 2.5 days a year at 2°C or colder. That's the air a heat pump draws its heat from on a winter morning.
Relief valves leak most
Water Corporation names hot water systems among its five household leak hotspots, usually through the relief valve. A valve that never stops running is worth showing to a plumber before the next bill.
Is there a WA rule against gas?
Not one we've found. Victoria has announced that from 1 March 2027, gas hot water in existing homes must be replaced with an efficient electric system once it reaches the end of its life. We haven't found anything like it for WA. As with any purchase, check current rules before you buy.
So the choice in Perth is about your house: what fuel is already there, where a unit can sit, and how much hot water you use. Our gas or heat pump tool and the hot water size guide help you narrow it down, and the hot water page compares every type.
What WA's rules ask for
Installing or replacing a water heater counts as major work under WA's plumbing regulations. The licensed contractor lodges a notice of intention at least 24 hours before starting, and you should have a certificate of compliance within five working days of the job finishing.
Repairing a water heater is minor work, which needs a record but no certificate. A restricted plumbing permit only covers a straight swap where no pipes change.
On a replacement or relocation, WA requires a temperature control device, with an exception for basins. Bathroom fixtures used for personal hygiene must not deliver more than 50°C, and stored water is kept at 60°C or above to control Legionella.
Gas units bring a second trade. Once the gas side is done, the gas fitter must give you a Notice of Completion within 48 hours, unless the work was only servicing.
Discounts in WA
We haven't found a WA state rebate for hot water. The national STC scheme does apply: eligible heat pumps under 425 L and solar water heaters under 700 L can create small-scale technology certificates, and owners often assign them to an agent for a discount or a delayed cash payment.
The model has to be on the register, and certificates are issued until the scheme ends in 2030. Our STCs page explains how it works.
Questions for a Perth hot water plumber
- Is your licence number on this quote, as WA requires?
- Will you lodge a notice of intention, and when will I get the certificate of compliance?
- Does this replacement need a tempering valve, and is it included?
- If it's gas, who does the gas side, and will I receive the Notice of Completion?
- Is this model on the STC register, and how much does assigning the certificates take off?
What we would do
If the system still heats at all, find out whether it's one part before you replace it: a repair is minor work in WA and needs no certificate. If it's finished, choose the next one while you can still compare gas, heat pump and solar calmly, rather than taking whatever is on the truck. Ask for one written quote that shows the licence number, the tempering valve and any STC discount. A plumber who specialises in hot water will know which paperwork your job needs.