Hot water problems: what each symptom points to
Name the symptom first. It decides which part is at fault, who you call and whether a new system is even on the table.
Most hot water problems are one of seven faults wearing different clothes. The mistake is to ring a plumber with "the hot water is playing up" and no more detail. A plumber who hears a symptom can bring the right part. One who hears a mood has to come twice.
Start with what you can see and feel at the taps. That narrows the list faster than any guess about the tank.
| What you notice | What it usually points to | Read next |
|---|---|---|
| No hot water anywhere | The heat source has stopped | No hot water: the checks that come first |
| No hot water in the shower only | That mixer, not the system | Shower only: it's the mixer |
| Warm but never properly hot | Thermostat or tempering valve | Hot water not hot enough |
| Weak flow on the hot side only | A blockage or valve on the hot line | Low hot water pressure |
| Water around the base of the unit | A leak, urgent or not depending on where | Your hot water system is leaking |
| Dripping from the relief valve | Normal expansion or a warning | Relief valve leaking |
| Brown water or a rotten egg smell | The tank, the anode or the mains | Brown hot water and smelly hot water |
Is the problem the whole house or one outlet?
Run the hot tap alone at the kitchen, the bathroom and the laundry. One dead or weak outlet is almost never the hot water system. It is that tap, that mixer or the pipe feeding it.
Every outlet affected is a different story. Now the system, its power or fuel supply, or a valve upstream of everything is the suspect. This single comparison separates a cheap fix from an expensive one more often than anything else on this page.
Does it happen all the time or only sometimes?
A fault that is constant has a constant cause, such as a failed part or a setting that has drifted. A fault that comes and goes follows something else: demand, weather, a power interruption or a household routine.
Hot water that runs out after a few minutes is a capacity or recovery question, not a breakdown. Hot water that vanished after a storm or a power cut is worth a look at the switchboard and any display on the unit. Write down when it changed. Plumbers ask for that first.
What you can check, and where you stop
The checks are simple. Look at the switchboard for a tripped circuit. Read any error code or warning light on the unit and note it down. Feel for dampness around the base and the pipes, without touching anything hot. Time how long the hot lasts.
That is the whole list. Replacing an element or thermostat, working on a tempering valve and any work on a gas appliance are licensed work in every Australian state and territory. Do not open covers, and do not adjust a thermostat to compensate for a poor shower. The setting is a safety margin, not a comfort dial.
Repair or replace?
Replacing a whole system for a fault that needs one part is the most expensive mistake in this category. A tank that is leaking from the body is usually finished. A tank with a failed thermostat, a worn valve or a dead element usually is not.
Ask the plumber to name the failed part and say why it cannot be replaced. If the answer is vague, get a second opinion before you agree to a new system.
What to tell the plumber
- Which outlets are affected, and which are fine.
- What it does: no heat, not enough heat, runs out, leaks or smells.
- When it started and what changed around then.
- The type and age of the system, if you know them.
Those four facts turn a diagnostic visit into a repair visit. If you would rather be walked through it, the hot water troubleshooter does the sorting for you.
Frequently asked questions
What are the most common hot water problems?
No hot water at all, water that is warm but never hot, hot water that runs out quickly, low pressure on the hot side only, leaks around the unit and discoloured or smelly water. Each has a different likely cause, so describe the symptom before you call anyone.
How do I know if my hot water problem is the system or just one tap?
Run the hot tap alone at every outlet. If only one is affected, the cause is that tap, its mixer or the pipe feeding it. If every outlet is affected, the system or its supply is the likely cause.
Can I fix a hot water problem myself?
You can check the switchboard, read any error code and note when the fault started. Repairs to elements, thermostats, valves and anything on the gas side are licensed work in every Australian state and territory, so leave them to a licensed tradesperson.
Should I replace my hot water system when it develops a fault?
Not automatically. Many faults come down to a single worn part such as a thermostat, a valve or an element. A tank that leaks from the body is usually at the end of its life. Ask the plumber which part has failed and why it cannot be replaced.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- Australian Government, energy.gov.au. Hot water systems — types, installation and energy performance
- NSW Fair Trading. Plumbers, drainers and gasfitters — licensing