No hot water from your bath tap is a frustrating problem, but it's often caused by something straightforward — a worn washer, a faulty cartridge, or an issue with your hot water system. Some checks are safe for homeowners to carry out themselves, while others must be handled by a licensed plumber. Here's how to work through the problem systematically.
Start With the Obvious: Check Other Hot Taps First
Before touching anything, turn on another hot tap in the house — the kitchen sink or bathroom basin. If no taps in the house have hot water, the problem is with your hot water cylinder or heating system, not the bath tap itself. If other taps run hot fine, the fault is isolated to the bath tap or its supply line.
- No hot water anywhere: Check your hot water cylinder's thermostat, element, or gas supply. This is likely a job for a licensed plumber or gasfitter — see below.
- Only the bath tap affected: Continue with the steps below.
Check the Hot Water Isolation Valve
Under the bath or in a nearby access panel, there is usually an isolation valve (also called a service valve) on the hot water supply pipe. These small valves can accidentally be turned off — especially after recent maintenance or renovations. The valve is open when the slot in the valve head runs parallel to the pipe, and closed when it runs across the pipe. Turn it to the open position and test the tap again.
Inspect the Tap Washer or Cartridge
If the isolation valve is open and you still have no hot water flow, the tap mechanism itself is likely the culprit. NZ bath taps generally fall into two types:
Traditional Jumper-Valve (Washer) Taps
These use a rubber washer on a brass jumper. Over time, the washer can swell, harden, or become dislodged, blocking flow entirely. Replacing a washer is a common DIY task:
- Turn off the water at the isolation valve (or at the toby/main if there's no isolation valve).
- Remove the tap handle (usually a screw under a decorative cap).
- Unscrew the headgear with a spanner.
- Replace the washer and jumper if worn.
- Reassemble and restore water supply.
Ceramic Disc or Cartridge Taps
Modern mixer taps and many single-lever bath taps use a ceramic cartridge. If the hot side of the cartridge fails or the cartridge seizes, you'll lose hot water flow. Cartridges are brand-specific — take the old one to Mitre 10 or Bunnings to match it, or contact the tap manufacturer directly. Replacement is similar to washer taps: isolate the water, remove the handle, extract the cartridge, and fit the new one.
Important: If you are not confident working with plumbing fittings, or if the tap is old and corroded, stop and call a professional. Forcing corroded fittings can cause leaks or burst pipes.
Check for a Blocked Strainer or Flow Restrictor
Some tap bodies have a small strainer or flow restrictor fitted inside the inlet. Sediment and scale — common in many NZ regions with harder water — can clog these over time. With the water isolated, remove the inlet fitting and check for a small mesh screen or plastic disc. Clean or replace it if blocked.
Hot Water Cylinder Issues
If the bath tap is the only outlet affected and the above checks don't resolve it, there may be a partial blockage in the hot water pipe running to the bath. Scale build-up, a kinked flexi-hose, or a failing cylinder dip tube can all restrict flow to specific outlets. Diagnosing pipe blockages and cylinder faults is best left to a licensed plumber — they have the tools to pressure-test and inspect pipework properly.
For information on hot water system requirements under the NZ Building Code (clause G12), visit MBIE Building Performance.
Healthy Homes and Rental Properties
If you're a landlord, be aware that the Healthy Homes Standards require rental properties to have hot water at a safe and functional temperature. A bath tap with no hot water flow could put you in breach of your obligations. Check the requirements at Tenancy Services.
When to Call a Professional
Some plumbing work in New Zealand is restricted work under the Plumbers, Gasfitters and Drainlayers Act 2006, meaning it must be carried out by — or supervised by — a licensed tradesperson registered with the Plumbers Gasfitters & Drainlayers Board (PGDB). This includes:
- Any work on your hot water cylinder (element replacement, thermostat, pressure relief valve).
- Connecting or modifying pipework within the wall or under the floor.
- Any gas water heating components.
Simple tasks like replacing a tap washer or cartridge on an accessible tap are generally considered maintenance and can be done by a competent homeowner — but if you're unsure, it's always safer to call a pro.
Safety note: Always isolate the water supply before opening any tap fitting. Never work on a pressurised system. If you smell gas near a gas hot water unit, do not attempt any work — ventilate the area and call a gasfitter immediately.
You can find qualified, local plumbers in your area on tradedirectory.co.nz.
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