"Tempering valve" and "thermostatic mixing valve" get used almost interchangeably on the tools, but they're built to two different standards for two different jobs, and AVG's range makes both. Getting the wrong one onto a commercial or aged-care job is a compliance problem, not just a part swap.
Tempering valve (AS4032.2): single-dwelling scald protection
A tempering valve — the AVG units behind our HotKit storage hot water kits and the Hot Water Valves collection — blends a fixed-ish outlet temperature for scald protection on a single dwelling's storage hot water system. It's built to AS4032.2, doesn't carry a disinfection function, and is the right default for a standard house.
Thermostatic mixing valve (AS4032.1): the healthcare/commercial standard
AVG's TMV range (TMV15-LF, TMV20-LF, TMV25HF-LF, $266.97/$305.28/$636.88) is built to the stricter AS4032.1 standard and carries a WaterMark certification to AS1357.2 (Lic 2639). The outlet temperature is adjustable 35-45°C from a 60-90°C hot supply, with a minimum 4 L/min flow — but the feature that actually separates it from a tempering valve is a manually selectable 65°C thermal flush (2-minute disinfection cycle), used to periodically purge warm-water dead legs of legionella risk. That function is why TMVs, not tempering valves, are specified for aged care, healthcare, schools and other multi-outlet commercial buildings where warm water sitting in pipework is a recognised risk.
The plumbed-in box (PIB): concealment, not a different valve
The PIB versions (TMV15-PIB-LF $540.26, TMV20-PIB-LF $603.82) are the same TMV pre-fitted into a 305mm square x 75mm deep stainless steel recessed wall box with a lockable hinged door, NSW Health Department approved and keyed alike across boxes for easier servicing across a building. The box doesn't change the valve's performance — it changes where and how it's installed: concealed behind a lockable door in a corridor, ward or public-facing wall where a standard exposed valve body would be either unsightly or tamper-prone. If the valve is going into a plant room or service riser nobody but a technician accesses, the standard TMV without the box is the simpler, cheaper choice.
Bypass variants
TMV15BP-PIB-LF and TMV20BP-PIB-LF add a cold-water bypass to the plumbed-in box, for sites running a hot water circulation system where the bypass is needed to maintain flow through the circulation loop. Three AVG tempering-valve PIB variants (TVA15C/TVA20C/TVA15CHP/TVA20CHP-PIB-LF) are currently DRAFT and not purchasable — worth checking back if a boxed tempering valve (rather than a boxed TMV) is specifically what the job calls for.
Frequently Asked Questions
What's the actual difference between a TMV and a tempering valve?
A tempering valve (AS4032.2) gives scald protection for a single dwelling's hot water. A thermostatic mixing valve (AS4032.1) adds a manually selectable thermal flush for periodic legionella disinfection and is WaterMark certified to AS1357.2, which is why it's specified for aged care, healthcare and other commercial multi-outlet buildings.
Why would I need the plumbed-in box (PIB) version instead of a standard TMV?
The PIB conceals the same valve in a lockable stainless steel wall box, which matters in a corridor, ward or other public-facing location where an exposed valve would be unsightly or tamper-prone. In a plant room or service riser, the standard TMV without a box is simpler and cheaper.
What does the thermal flush/disinfection function actually do?
It's a manually selectable 65°C, 2-minute flush cycle that purges warm water sitting in pipework, reducing the legionella risk that can build up in warm-water dead legs between normal use.
Is there a bypass version, and when do I need it?
Yes — TMV15BP-PIB-LF and TMV20BP-PIB-LF add a cold-water bypass inside the box, needed on sites running a hot water circulation system to maintain flow through the circulation loop.