In New Zealand, installing a water pressure reducing valve (PRV) is restricted plumbing work under the Plumbers, Gasfitters, and Drainlayers Act 2006. This means it must be carried out by — or under the direct supervision of — a licensed plumber. Attempting to do it yourself is not only illegal but could void your home insurance and cause serious damage to your plumbing system.
What Is a Water Pressure Reducing Valve?
A pressure reducing valve (PRV) is a device fitted to your incoming water supply that reduces mains water pressure to a safe, consistent level for your home's plumbing. In many parts of New Zealand, mains water pressure can exceed 800 kPa, which is far too high for standard household fittings and appliances. The NZ Building Code (specifically clause G12 – Water Supplies) requires that water pressure at outlets does not exceed 500 kPa, and a PRV is the standard way to achieve this.
Without a correctly installed PRV, you risk:
- Burst pipes and fittings
- Damaged appliances (washing machines, dishwashers, hot water cylinders)
- Noisy "water hammer" in your pipes
- Reduced lifespan of tapware and valves
Why Is This Restricted Work in NZ?
Under the Plumbers, Gasfitters and Drainlayers Board (PGDB) licensing framework, any work that connects to or modifies your home's pressurised water supply is classified as restricted sanitary plumbing work. This includes:
- Fitting or replacing a PRV on the toby (main water supply) or internal pipework
- Adjusting or modifying existing pressure control equipment
- Any work on pipes that form part of the building's water supply system
Only a registered or licensed certifying plumber can legally carry out and certify this work. You can verify a tradesperson's licence on the PGDB website.
What Can a Homeowner Do?
While you cannot install the PRV yourself, there are a few things you can legally and safely do:
- Check your water pressure using an inexpensive pressure gauge (available at Bunnings or Mitre 10) fitted to an outdoor tap. This helps you understand whether high pressure is actually your problem before calling a plumber.
- Identify your toby location so the plumber can work efficiently.
- Research PRV options and discuss preferences with your plumber — common brands available in NZ include Honeywell and Watts, though your plumber will advise on the most suitable product for your situation.
- Monitor your system after installation and report any changes in pressure or performance to your plumber.
⚠️ Safety note: Never attempt to cut into pressurised water supply pipes or tamper with your toby valve beyond simply turning the water on or off. High-pressure water can cause serious injury and significant property damage.
What Does a Plumber Actually Do?
When a licensed plumber installs a PRV, the job typically involves:
- Isolating the water supply at the toby
- Cutting into the incoming supply pipe at an appropriate location (usually near the toby or where the pipe enters the house)
- Fitting the PRV, along with isolation valves and sometimes a pressure gauge for future monitoring
- Setting the PRV to the correct outlet pressure (commonly 350–500 kPa for residential use)
- Testing the system and issuing a Certificate of Compliance for the work
The Certificate of Compliance is an important document — keep it with your property records. It confirms the work meets the NZ Building Code and MBIE Building Performance requirements.
Does a PRV Installation Need a Building Consent?
In most cases, fitting a PRV is exempt from building consent under Schedule 1 of the Building Act 2004, as it is routine plumbing maintenance and repair work. However, always confirm this with your local council before work begins, as exemptions can depend on the scope of work and your specific situation.
How Much Does It Cost? (Rough Guide)
As a general guide only, expect to pay somewhere in the range of $300–$700 for a straightforward PRV installation, including parts and labour. Costs vary depending on your location, ease of access to the pipework, and the plumber's call-out rates. Get at least two quotes from licensed plumbers.
When to Call a Professional
You should call a licensed plumber if you notice any of the following:
- Banging or hammering noises in your pipes when taps are turned off
- Dripping relief valves on your hot water cylinder (a common sign of excess pressure)
- Appliances failing prematurely or leaking at connections
- Unusually high water bills that could indicate pressure-related leaks
- Your pressure gauge reads above 500 kPa
You can find qualified, local plumbers on tradedirectory.co.nz — look for someone who is PGDB-licensed and experienced with residential water supply work.
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