If you’re planning a hot water cylinder replacement in NZ, you may have been told that a simple “like-for-like” swap is no longer allowed. That’s because modern installations must now meet current safety standards under the New Zealand Building Code, including the use of a safe tray and 40mm drain.
These requirements are designed to protect your home from water damage and ensure your plumbing system is compliant, safe, and future-proof.
NZ Building Code Requirements for Hot Water Cylinders
Under the New Zealand Building Code, particularly Clause G12 (Water Supplies) and E3 (Internal Moisture), all plumbing systems must safely manage water leaks, overflows, and discharges.
For hot water cylinders, this typically means:
Installing a safe tray under the hot water cylinder
Connecting the tray to a minimum 40mm drain
Ensuring any discharge is directed to a safe and visible location
These are standard expectations for a compliant hot water cylinder installation in NZ and are commonly required during upgrades or replacements.
Why Safe Trays and 40mm Drains Are Important
Many homeowners don’t realise how much water a failed cylinder can release. Without proper protection, even a small leak can cause serious damage.
Installing a hot water cylinder safe tray and drain helps to:
Prevent water damage to floors, walls, and cabinetry
Reduce the risk of mould and moisture issues
Ensure leaks are safely contained and discharged
Meet NZ plumbing compliance requirements
A 40mm drain is specifically required because it can handle high volumes of water quickly, reducing the chance of overflow.
Like-for-Like Cylinder Replacements: What’s Changed?
In the past, a like-for-like hot water cylinder replacement often meant swapping the old unit for a new one in the same location with minimal changes.
Today, that’s no longer the case.
When replacing a cylinder, the installation must generally meet current NZ Building Code requirements, even if the original system didn’t. This means:
Older setups without a safe tray or drain usually need to be upgraded
A compliant drain solution must be installed where required
The overall system must meet modern plumbing standards in NZ
This is why many “simple” replacements now involve additional work.
No Safe Tray? This Can Be an Issue When Selling Your Home
If your hot water cylinder does not have a safe tray and compliant 40mm drain, it can create complications when it comes time to sell your property.
During pre-sale inspections or building reports, non-compliant plumbing, such as a missing hot water cylinder safe tray is often flagged. This can:
Raise concerns for potential buyers
Lead to requests for repairs or price reductions
Delay settlement while issues are resolved
In some cases, buyers may request that the system be upgraded to meet current NZ Building Code requirements before completing the purchase. Addressing these issues early with a compliant hot water cylinder installation can help avoid stress and protect your property value.
No Safe Tray? It Could Impact Your Insurance
A hot water cylinder installed without a safe tray and compliant 40mm drain can also create issues with your home insurance. Insurers generally expect plumbing systems to meet current standards and to include reasonable protections against water damage. If a cylinder fails and causes flooding, and it’s found that there was no safe tray for the hot water cylinder or inadequate drainage, this may affect how a claim is assessed. In some cases, insurers could reduce a payout or decline a claim if the damage is linked to a non-compliant or poorly protected installation. Ensuring your system includes a compliant safe tray and drain setup helps protect not just your home, but also your ability to make a successful insurance claim if something goes wrong.
What If You Can’t Install a 40mm Drain?
In some homes, installing a 40mm drain for a hot water cylinder isn’t practical, especially in:
Homes with concrete slab floors
Cylinders located in the middle of the house
Areas without access to suitable drainage
If this is the case, a common and effective solution is a hot water cylinder relocation to outside.
Benefits of Installing an Outdoor Hot Water Cylinder
Choosing an outdoor hot water cylinder installation in NZ can solve compliance issues while offering added benefits:
Easier to meet drainage and overflow requirements
Lower risk of internal flooding or water damage
Frees up valuable indoor space
Provides better access for maintenance and servicing
Outdoor cylinders are becoming increasingly popular as a practical and compliant solution for modern homes.
Need Help with a Hot Water Cylinder Upgrade?
If you’re considering a hot water cylinder replacement, it’s important to understand how the latest NZ plumbing regulations affect your installation.
Whether you need:
A safe tray and 40mm drain installed
Advice on compliance requirements
Or a relocation of your cylinder outdoors
A professional assessment will ensure your system is safe, compliant, and built to last.
