Low water pressure throughout the whole house is one of those frustrations that affects everything from your morning shower to filling the kitchen sink. Unlike a single tap running slowly, whole-house pressure issues usually point to something upstream — either the mains supply, your meter, your pipes, or a pressure-reducing valve. The good news is that many causes are straightforward to identify, and some are easy to fix yourself.
How Water Pressure Works in a NZ Home
Water pressure is measured in kilopascals (kPa). In New Zealand, your local council or water supplier is generally required to deliver water to your property boundary at a minimum pressure, though the exact figure varies by region. Inside your home, pressure can be further affected by your internal pipework, fittings, and any pressure-control devices installed.
A static pressure of around 200–500 kPa at the boundary is typical for most urban NZ properties, but your experience at the tap depends on what happens between the street and your fixtures.
Common Causes of Whole-House Low Pressure
1. Low Mains Supply Pressure
If your neighbours are also experiencing low pressure, the issue likely lies with your water supplier. Mains pressure can drop during peak demand times (early morning, evening), after nearby works, or due to a fault in the network. Contact your local council or water utility first to rule this out.
2. Partially Closed or Faulty Toby Valve
Your toby valve (the main shutoff at the boundary) may not be fully open. This is especially common after recent plumbing work or if the valve is old and corroded. Locate your toby box (usually near the footpath or driveway) and check the valve is fully open. If it's stiff or damaged, contact your council or a licensed plumber — the toby and the pipework up to your boundary is often council-owned.
3. Pressure-Reducing Valve (PRV) Issues
Many NZ homes — particularly those on steep sections or with high mains pressure — have a pressure-reducing valve installed to protect appliances and fittings. Over time, PRVs can fail, wear out, or be set incorrectly, causing pressure to drop throughout the house. A licensed plumber can test and adjust or replace your PRV.
4. Corroded or Scaled Pipes
Older homes, particularly those built before the 1970s, may have galvanised steel pipes that corrode from the inside over time. The build-up of rust and scale narrows the pipe bore and restricts flow. If your home has galvanised pipes and is showing its age, repiping with copper or modern CPVC/PEX may be the long-term solution. BRANZ has useful guidance on older NZ housing materials and maintenance.
5. Leaks in the Supply Line
A significant leak between the toby and your house can bleed off pressure before water even reaches your taps. Signs include an unexplained spike in your water bill, damp patches in the lawn, or the sound of running water when everything is turned off. Check your water meter: if the dial is moving with all taps off, you likely have a leak.
6. Shared Supply Lines
In older subdivisions or multi-unit properties, several homes may share a single supply pipe. If a neighbour has added high-demand appliances or if the shared pipe is undersized for current use, everyone on that line can experience lower pressure.
7. Hot Water System Restrictions
If low pressure is mainly on the hot water side, the cause may be your hot water cylinder, a faulty tempering valve, or a blocked filter on the inlet. Mains-pressure hot water systems (common in newer NZ homes) should deliver similar pressure to cold; low-pressure (gravity-fed) cylinders are designed to operate at lower pressure and may need a pump if you want better flow.
What You Can Check Yourself
| Check | How to do it | DIY-friendly? |
|---|---|---|
| Toby valve position | Locate toby box, check valve is fully open | Yes |
| Water meter leak test | Turn off all taps, watch meter dial | Yes |
| Aerator/filter screens | Unscrew tap aerators and rinse clean | Yes |
| Showerhead flow | Remove and soak in vinegar to descale | Yes |
| PRV adjustment | Locate PRV, check manufacturer setting | Caution — call a plumber |
| Pipe inspection | Visual check for obvious corrosion | Yes (surface only) |
Note that while cleaning aerators and showerheads can help individual fixtures, if pressure is low at every outlet simultaneously, the problem is almost certainly upstream of your fittings.
Improving Pressure: Your Options
- Pressure-boosting pump: A pump can be installed on your incoming supply to boost pressure throughout the house. This is restricted plumbing work and must be carried out by a licensed plumber.
- PRV replacement or adjustment: Again, this is work for a licensed professional.
- Repiping: If corroded pipes are the culprit, a full or partial repipe is a significant job requiring a licensed plumber and, depending on scope, a building consent under the NZ Building Code.
- Contact your water supplier: If the issue is at the mains, your council may be obligated to investigate and remedy it.
When to Call a Professional
Under New Zealand law, plumbing work — including work on supply pipes, pressure valves, hot water systems, and drainage — is restricted work that must be performed by a Licensed Building Practitioner or a plumber registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB). Unlicensed plumbing work can void your home insurance and create liability issues when you sell.
Call a licensed plumber if:
- You suspect a burst or leaking supply pipe
- Your PRV needs replacing or adjusting
- You want a pressure-boosting pump installed
- Your pipes are old galvanised steel
- Pressure has dropped suddenly without obvious cause
You can find qualified, local plumbers in your area on tradedirectory.co.nz.