Symptoms and their likely causes
| Often caused by | Usually | |
|---|---|---|
| No hot water at all (electric) | A tripped circuit, a failed element or a faulty thermostat | A repair |
| Hot water, but not hot enough | A thermostat or element fault, or a faulty tempering valve (Rheem lists this one) | A repair |
| Hot water runs out early | A failed element, or a cylinder too small for the household | A repair, unless it's the size |
| A drip or trickle from a valve or its drain pipe | A valve that needs servicing or replacing | A repair |
| No hot water (gas) | The gas supply, the ignition or the gas controls | A gasfitter's repair |
| Water from the tank body | The tank itself has failed | A replacement |
Safe checks before you book
You can
- Look at the switchboard. If the hot water circuit breaker has tripped, reset it once. If it trips again, leave it off.
- On gas, check that your other gas appliances work and, on LPG, that the bottle isn't empty.
- Look at the cylinder, its valves and the floor or safe tray for water, and take photos.
- Note when it started and whether every hot tap is affected or just one.
- Find the label with the model and serial number.
Leave to an authorised tradie
- Taking off covers to reach an element or thermostat.
- Testing, adjusting or replacing valves.
- Anything on the gas side of a gas heater.
- Changing the temperature setting.
How a plumber will track it down
Ask what changed
A plumber will ask about the symptoms, roughly how old the cylinder is and what you've already reset, then read the label.
Test the heating side
On an electric cylinder that means testing the element and thermostat, with an electrician for the wiring where it's needed. On a gas heater, an authorised gasfitter checks the supply and controls.
Check the valves
A sticking tempering valve can feel exactly like a heating fault at the shower, so the valves get checked too.
Judge the tank
Any weeping from the tank body moves the conversation from repair to replacement.
Give you the choice
You should hear what failed, what fixing it involves, and whether the tank is close to the end regardless.
Rules that apply to a repair
Repairing or maintaining an existing water heater with comparable products is one of the Building Act's consent exemptions (Schedule 1 clause 36). Like the other exemptions in that part of the schedule, it holds only when an authorised person does the work, and the repaired cylinder still has to meet the Building Code.
Clause G12 of the Code expects anything that stores hot water to have safety features that relieve excessive pressure and limit temperature, so a rupture can't produce flash steam. That's why the valves on a cylinder are never something to block, cap or remove.
Rheem says repairs that need covers or casing taken off with tools should only be done by a suitably qualified plumber, gasfitter or electrician. Gas repairs are gasfitting, which only an authorised gasfitter may do. Our guide to checking a PGDB licence shows how to look someone up.
For the bigger picture, start at our hot water cylinders page.
Red flags on a repair call
- A valve that has been capped or plugged to stop it dripping.
- Being told the tank is finished without being shown where it leaks.
- Pressure to sign for a new cylinder on the spot, with no repair price offered.
- Advice to turn the thermostat down yourself to save power.
- No practising licence to show when you ask.
What we would do
If the tank is dry and sound, fix the part. If the tank itself is weeping, put the money toward a replacement instead of a repair it won't outlive. Either way, ask a hot water repair specialist to show you the failed part or the leak before you decide.