Lukewarm shower? Hot water that's suddenly weaker than it used to be on a unit you know is fine? It's often the tempering valve — a small mixing valve required by AS3500 on every hot water delivery to bathrooms in Victoria, with a 5-7 year service life. When they fail they fail unexpectedly, and the symptom is "all the hot water's gone". Prime Plumbing & Gasfitting replaces tempering valves across Melbourne, with the new valve set to the AS3500-required 50°C delivery temperature.
The classic mis-diagnosis: a customer calls saying the hot water unit is dead, gets quoted for a new unit, replaces it, and the new unit gives the same lukewarm shower. The valve is the culprit, not the unit. Prime Plumbing & Gasfitting always checks the tempering valve before recommending hot water unit replacement. A $250+ GST valve replacement is a lot less than a $2,500+ GST new hot water unit, and we'd rather you spend the right money on the right thing.
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AS3500 requires hot water delivery to bathrooms (basin, bath, shower) capped at 50°C. The tempering valve is set on install — we use a calibrated thermometer at the bathroom outlet during commissioning to confirm. Set too low and the shower is lukewarm; set too high and there's a scald risk. The right number is 50°C at the basin tap.
Different hot water configurations need different tempering valve specs. Gas storage with a 60°C tank delivers different inlet conditions than a heat pump with a slightly lower tank temperature. We match the replacement valve to the unit; using a generic valve on every install causes mid-shower temperature swings.
Tempering valve replacement is licensed plumbing work — BPC Compliance Certificate (#103414). The certificate is sometimes asked for at sale (particularly on healthcare or aged-care properties) and is part of the routine documentation we email after every Prime Plumbing & Gasfitting visit.
Before the valve, we check the unit's outlet temperature — sometimes the unit itself is the issue and not the valve. Five minutes at the unit confirms which is which.
Hot and cold isolations on the valve are closed, valve drained back to atmosphere, removed from the union connections. We document the make and model of the old valve in case there's a warranty claim possible.
New tempering valve is fitted with new union washers (we don't reuse old washers — they harden over the valve's service life and don't seal cleanly on a new install). Hot and cold isolations reopened.
The hot water draw is run at the closest bathroom basin while we adjust the valve. Calibrated thermometer at the basin outlet confirms 50°C. The valve's adjustment cap is then locked or sealed per AS3500 (so it can't drift).
Hot water at all bathroom outlets is tested in turn — basin, bath, shower — to confirm consistent delivery temperature. BPC Compliance Certificate emailed as a PDF along with the calibration record.
Making sure your kitchen is prepared and ready for a gas cooktop installation saves everyone time. We've put together an in depth guide that details all the steps you can take for a seamless install: Gas Cooktop Installation Guide: Preparing Your Kitchen
Below are 4 points that we look for:
We help you select the right size and configuration for your space and cooking style.
We confirm whether your bench requires modification before installation begins.
Most gas cooktops need a power outlet for ignition. We check access and setup before installation.
Clear access to the workspace and gas meter allows us to complete your installation smoothly.
Most replacements run $280-$420 + GST supplied-and-installed. Variation is access (an under-floor valve takes longer than a wall-mounted one) and brand match (a unit-specific valve costs more than a generic). On-site quote in writing. *Pricing depends on lots of factors — every job is different. Budget for the higher side of the range; we'll quote the actual price on site.
Quick test: turn on a hot tap at the kitchen sink (not bathroom). If the kitchen runs hot but the bathrooms are lukewarm, the issue is the valve, not the unit. Kitchen taps are usually not tempered, so they bypass the valve and show the unit's real output.
Yes — AS3500 requires hot water delivery to bathroom fixtures (basin, bath, shower) capped at 50°C in residential settings, 45°C in some healthcare and aged-care contexts. Without a tempering valve, delivery from a 60°C tank exceeds the regulatory cap.
Manufacturer service life is 5-7 years on most residential models. Hard water (not common in Melbourne but occasionally relevant) shortens that. Valves don't often fail before 5 years; almost always do before 10.
No — tempering valve installation is licensed plumbing under BPC, and the calibration to AS3500 50°C requires a calibrated reference thermometer. The cost saving from DIY isn't real once you account for buying the calibration gear and sourcing a compliant valve.
Sometimes. Heat pumps store water at a slightly lower temperature than gas storage, and some heat pump installs use a different tempering valve spec. We match the valve to the unit type.
Standard install is on the hot water outlet of the unit. Wall-mounted is easiest to service; under-floor or in-wall installs work but are slower to reach for replacement. If your old valve is in a hard-to-access location, we can sometimes relocate during the replacement — discussion at quote stage.
