No hot water is one of the most stressful household problems — especially in winter. But before you call a plumber, you can often diagnose (and sometimes fix) the problem yourself in minutes.
The first step is knowing what type of system you have.
Step 1 — Identify Your System
Electric hot water cylinder — a large insulated tank (typically 180–250L) in your hot water cupboard or ceiling space. Has an electrical connection box at the bottom. Most common type in NZ homes.
Gas califont / continuous flow — a wall-mounted unit (usually outside or in a garage/laundry) that heats water on demand. Runs on natural gas or LPG. No storage tank — water is heated as it flows through.
Heat pump hot water cylinder — looks like a regular cylinder but has a fan/compressor unit on top. Electrical, but uses heat pump technology. Less common but increasingly popular.
Wetback — a coil inside a wood burner that heats water via your cylinder. If the fire isn't lit, water won't heat via the wetback (though many homes have an electric element as backup).
Solar hot water — roof-mounted panels heat water into a cylinder. Works well in summer but needs a boost element (electric or gas) for cloudy days and winter.
Electric Hot Water Cylinder — What to Check
1. Check the circuit breaker
Go to your switchboard. Find the breaker labelled "Hot Water", "HWC", or "Cylinder". If it's tripped (in the middle position), flip it fully off, then back on.
If it trips again immediately: there's a fault in the system. Call a plumber.
2. Check the thermostat
The thermostat dial on the cylinder is usually behind a small panel at the bottom. It should be set to 60°C. If it's been knocked to a very low setting, turn it up and wait 2–3 hours.
3. Off-peak/night rate cylinder?
Some cylinders are on a ripple control circuit and only heat during off-peak hours (typically overnight, 11pm–7am). If yours is on this system, the cylinder may simply not have heated yet today — check the next morning.
4. What you can't fix yourself
- Replacing a failed heating element → needs a plumber or electrician
- A continuously tripping breaker → electrical fault, call a plumber/electrician
- A leaking cylinder → call a plumber
Gas Califont — What to Check
1. Check the gas supply
Is your gas account up to date? Have other gas appliances (cooktop, oven) stopped working too? If yes, call your gas retailer.
LPG cylinder: check if the cylinder is empty. If you have two cylinders, the changeover valve should automatically switch — make sure it's set to "Auto" or "Reserve". If both are empty, order a refill.
2. Check the gas isolation valve
There should be a ball valve on the gas pipe leading to the califont. It should be parallel to the pipe (open). If it's perpendicular (closed), open it.
3. Pilot light (older units)
Older gas califonts have a pilot light. If it's blown out, you can relight it — instructions are usually on a sticker on the unit or in the manual. Modern califonts have electronic ignition and no standing pilot.
4. Error code on the display
Modern califonts (Rinnai, Rheem, Bosch) show error codes. Google your model number + error code for the specific cause.
5. What you can't fix yourself
Any gas repair, gas line work, or flue work must be done by a licensed gasfitter in NZ. Gas work is not DIY.
Heat Pump Hot Water Cylinder — What to Check
Check the circuit breaker first. Heat pump cylinders also have an element backup — if the heat pump component fails, the element should take over (slowly). Check for error codes on the display panel. Most faults require a technician.
When You Need a Plumber — and What It Costs
| Problem | Typical cost |
|---|---|
| Replace electric heating element | $200–$500 |
| Replace thermostat | $150–$350 |
| Replace pressure relief valve | $150–$400 |
| Emergency callout (evenings/weekends) | $150–$250 callout + time |
| Replace electric cylinder (180L, installed) | $1,500–$2,800 |
| Replace gas califont (installed) | $1,200–$2,500 |
| Replace with heat pump cylinder (installed) | $3,000–$5,000 |
Is your cylinder more than 15 years old? An element replacement might buy you a few more years, but cylinder failure (leaking or bursting) tends to follow element failures in older units. Get a plumber's opinion on whether repair or replacement makes more sense.
While You're Waiting for the Plumber
- You can boil water for dishes
- Cold showers are uncomfortable but safe
- Most motels and gyms will let you use their facilities in a genuine emergency
- Hardware stores sell portable gas camping showers for multi-day outages
Finding a Plumber
If it's after hours and you have a leak as well as no hot water, that's an emergency — you want a plumber who takes emergency callouts. Expect to pay an after-hours callout fee on top of the job cost.