Hot water problems are one of the most common reasons Kiwis call a plumber. Whether you’re suddenly showering in cold water or your cylinder is making strange noises, most issues come down to a few common causes. Here’s a quick guide to help you understand what might be going wrong — and when it’s time to call a professional.
1. No Hot Water at All
If your taps are running cold, the cause is usually one of the following:
- Faulty thermostat
- Failed heating element
- Tripped switch or power fault
- Gas supply issue (for gas systems)
What you can check:
- Ensure the switch on the cylinder is ON
- Check your switchboard for a tripped breaker
If everything looks normal, it’s time for a qualified plumber or gasfitter to diagnose the fault safely.
2. Water Not Hot Enough
When the water heats, but not fully, common causes include:
- Thermostat set too low
- Sediment build-up inside the cylinder
- Ageing or worn-out heating element
- Hot water cylinder too small for household needs
Tip: NZ building code recommends storing hot water at 60°C to prevent bacteria growth.
3. Running Out of Hot Water Quickly
If you used to have plenty of hot water but now run out fast, the system may be struggling.
Likely reasons:
- A failing element (only one is working)
- Increased household use (extra people, longer showers)
- Damaged or blocked tempering valve
- Cylinder reaching end of life
If the issue develops suddenly, it’s usually a fault — not usage.
4. Water Pressure Problems
Low hot water pressure is a common issue in older Auckland homes with low-pressure cylinders.
Causes include:
- Blocked filters or valves
- Failing pressure-reducing valve
- Old copper cylinders that need upgrading
Solution: Many homeowners switch to a mains pressure hot water cylinder for stronger, consistent flow.
5. Hot Water Cylinder Leaking
A leak is never a good sign.
Common causes:
- Rusted or corroded cylinder
- Faulty pressure relief valve
- Failing pipe fittings
- Damaged cylinder base
If you notice water pooling around your cylinder, turn it off and call a professional immediately — leaks can cause major property damage.
6. Strange Noises From the Cylinder
Banging, hissing, popping, or rumbling sounds may mean:
- Sediment build-up
- Pressure problems
- Overheating issues
- Failing elements
- Sediment build-up is extremely common in NZ due to mineral content in local water supplies.
7. Smelly or Discoloured Hot Water
If your hot water smells like sulphur or appears rusty:
- The cylinder may be corroding
- The anode rod may need replacing
- Bacteria could be present in stagnant water
Rust-coloured water usually means the cylinder is old and needs replacing.
When to Call a Professional
Contact a certified plumber or gasfitter if you notice:
- No hot water
- Leaks around your cylinder
- Water discolouration or unusual smells
- Sudden pressure drops
- Gas hot water system faults
- Tripped power that keeps happening
Hot water systems can be dangerous if handled incorrectly — especially gas systems or high-pressure cylinders.
Need Hot Water Repairs or Upgrades?
ProSpec Plumbing & Gas offers:
- Hot water cylinder repairs
- Mains pressure upgrades
- Gas hot water installation
- Element and thermostat replacement
- Tempering valve repairs
- 24/7 emergency service
Call 021 029 4648 for fast, reliable hot water repairs across Auckland.