What the November 2024 Building Code Update Means for Your Hot Water System
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Understanding the Recent Changes to NZ Plumbing & Hot Water Regulations
From 1 November 2024, the updated version of G12/AS1 — part of the New Zealand building regulations governing water supplies — introduces important changes affecting domestic hot water systems.
Most notably: the maximum allowed hot-water temperature delivered at taps used for personal hygiene (bathrooms, showers) has been lowered from 55 °C to 50 °C.
This change aims to improve safety, particularly for vulnerable users such as children or the elderly, by reducing the risk of scalding.
At the same time, water storage tanks must still store water at at least 60 °C — to ensure hygiene and prevent bacterial growth (e.g. risk of Legionella).
What You Need to Know — Impact on New Installations & Replacements
If you are installing a new hot water cylinder — or replacing an existing system — here are the key implications of the regulation change:
- A tempering valve (or thermostatic mixing valve) is now required in any new installation or replacement to reduce water temperature at points of use (taps, showers) to no more than 50 °C.
- Stored water temperature remains at 60 °C — cylinder thermostats and heating elements must ensure water is hot enough for safe storage and bacterial control.
- “Low-to-low” (low-pressure) systems are also affected — even older, simpler systems require a tempering valve if replaced under the new rules.
- Changes apply only for new or replaced systems — existing cylinders already installed before 1 Nov 2024 are not automatically required to be upgraded, though retrofitting a tempering valve is advisable for safety. In essence: the update increases safety standards for hot water delivery, particularly in homes with vulnerable users — something all homeowners should take seriously.
Why These Changes Are Important — Safety, Compliance & Peace of Mind
The lowered tap-water temperature limit helps prevent scald injuries — a real risk, especially in multi-generational households, with children or older residents. Reducing the risk of burns while maintaining sufficient stored hot-water temperature strikes a balance between safety and hygiene.
At the same time, compliance with the updated building code ensures your hot water system meets current standards — an important consideration if you sell your home, make renovations, or need compliance documentation.
Additionally, the requirement for tempering valves means that water delivered to taps is safer, while still preserving stored water at hygienic levels (≥ 60 °C). It’s a simple but highly effective safety upgrade.
What Homeowners Should Do — Checklist Before Installing or Upgrading
If you are considering installing a new hot water cylinder, or replacing an existing one, here is what to do:
- Ensure a tempering valve or thermostatic mixing valve is included in the installation — especially if water is used for showers, baths, or basins.
- Verify the storage tank thermostat is set to keep water at 60 °C — to prevent bacterial growth while complying with safety regulations.
- If you have a low-pressure system and plan to keep it (or replace it), consider whether upgrading to a modern cylinder or installing a tempering valve may improve safety and compliance.
- Use a qualified plumber or hot-water specialist familiar with the updated code — to ensure installation is compliant, and paperwork/documentation is in order.
- For existing systems, consider a retrofitted tempering valve if the system hasn’t been updated — especially useful in homes with children or elderly.
Why The Cylinder Guys Are Your Trusted Partner for Compliance & Safety
At The Cylinder Guys, we stay up to date with regulatory changes — so your installation is always compliant and safe. When you work with us, we ensure:
- We install cylinders to meet the updated G12/AS1 requirements, including tempering valves where needed.
- We set thermostats correctly (storage 60 °C, tap output 50 °C) to balance hygiene and safety.
- We guide you on maintenance, safety best-practices, and compliance documentation — useful for insurance or when selling your home.
- We offer assessments and upgrades for existing systems to bring them in line with current code.
If you plan to install or replace your hot water cylinder soon — contact us today. We’ll make sure your hot water setup is not only efficient and reliable, but also compliant and safe under the 2024 regulations.