What each part does
| Its job | Signs it has failed | |
|---|---|---|
| Element | Heats the water in an electric storage tank | No hot water or lukewarm water; a safety switch that trips |
| Thermostat | Switches the element or gas burner on and off to hold the set temperature | Water too hot, too cold, or none at all |
| Anode | A metal rod that corrodes so the tank doesn't | Rusty or smelly hot water; an old tank never checked |
| Relief valve | Lets water out if pressure or temperature climbs too high | Constant dripping, or a valve that won't reseat |
Anodes and your water
An anode is meant to wear away. Dux, one manufacturer, says an anode's life span is limited and will decrease with a rise in temperature and worsening water quality. PlumbMatch isn't affiliated with Dux.
Dux designs its heaters for water with total dissolved solids (TDS) under 2500 mg/L. Where TDS is over 600 mg/L, it says the magnesium alloy anode may need replacing with an aluminium alloy one, and its warranty excludes tanks where TDS is above 2500 mg/L.
Other makers set their own rules. Ask your plumber, or the manufacturer, how often your model's anode should be checked and which type suits your water.
Thermostats and the 60°C line
A thermostat that drifts low isn't a saving. The building regulator warns that turning storage down will promote the growth of Legionella, which is why the plumber sets the tank to hold 60°C or more.
In Queensland, Queensland Health says any change to thermostat settings should be done by a licensed electrician. The temperature at the shower is a separate matter, handled by a tempering valve.
What a plumber will do
Isolate it
A plumber will switch off the power or gas and the water, and release the pressure before opening anything.
Test the part
Elements and thermostats are tested with a meter, not swapped on a hunch.
Check the anode
On an older tank, the anode is pulled out and inspected. A worn one is replaced with the type that suits your water.
Refill and check
The tank is refilled, air is bled from the taps, and the temperature is checked once it has heated.
Before you call
You can
- Note the symptoms and when they started.
- Check the circuit and safety switch at the switchboard.
- Copy the model number from the label so the right part can be ordered.
- Ask your water supplier about water quality if anodes seem to wear fast.
Leave to a licensed plumber
- Opening any cover on the unit.
- Element and thermostat changes, which involve mains power.
- Pulling and replacing the anode.
- Replacing the relief valve.
Who may do the work
Western Australia spells out the plumbing a homeowner may do: shower heads, taps other than thermostatic mixing taps, cistern washers, filter cartridges and plunging a blocked fixture or waste pipe. Hot water parts aren't on that list. Everything else must be done by a licensed plumber or permit holder.
In NSW, the Public Register shows a contractor's licence categories, expiry date and any conditions, so you can see that plumbing is covered before you book. Other states: our licence guide.
Questions to ask the plumber
- Which part failed, and how did you test it?
- Is the tank sound enough to be worth the part?
- When was the anode last checked, and which type suits our water?
- Is the replacement part from the original maker?
- Will the tank still store at 60°C or more after the repair?
What we would do
On a sound, dry tank, replacing a part is usually the right call. Ask for the anode to be checked whenever the cover is off, because a fresh anode is what stops the tank itself from rusting through. A plumber who specialises in hot water is likely to have the common elements and thermostats on the van, which can save a second visit.