Hot Water Guides

Hot Water Safety Checks: Gas, Pressure & Scald Risks

A hot water system is pressurised, often gas-fired, and delivers water hot enough to scald — so a few safety basics genuinely matter. Here's a plain hot water system safety check: what's safe to look at yourself, what the warning signs are, and when to call a licensed pro.

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Why it matters

The three real safety risks

Most of the time a hot water system just works, quietly, for years. But three risks are worth understanding, because the warning signs are easy to miss until they're serious: gas (and carbon monoxide), pressure, and scalding.

None of this is about doing repairs yourself — the opposite. The point of a hot water system safety check is knowing the signs, doing the few safe checks a homeowner can, and knowing exactly when to stop and call a licensed professional.

See also: servicing

Homeowner checking a hot water system for safety warning signs
The three risks

Gas & carbon monoxide, pressure, and scalding

What each risk looks like, and why it matters.

Gas & carbon monoxide

A gas system should burn with a clean blue flame. A yellow or sooty flame, black marks around the unit, or symptoms like headaches, nausea or dizziness when it's running can signal carbon monoxide — which is colourless and odourless. This is a stop-and-call-a-professional situation.

Pressure & relief valves

The TPR (temperature-pressure relief) valve protects the tank. A little discharge while heating is normal; constant streaming means a fault or excess pressure. Banging pipes or a relief valve running non-stop points to a pressure problem that needs a licensed plumber.

Scald protection

Water is stored hot enough to scald, so a tempering valve blends it down to a safe maximum of 50°C at your bathroom taps. If your hot water suddenly runs dangerously hot, the tempering valve may have failed — treat it as urgent.

Safe vs stop

What you can check vs when to call a pro

Stay on the safe side of this line — the checks on the left are fine; anything on the right is a licensed job.

Safe for a homeowner

  • Look for a clean blue gas flame vs yellow/sooty.
  • Note whether the relief valve drips constantly or just while heating.
  • Check hot tap temperature isn't dangerously hot.
  • Keep the area around the unit clear and ventilated.

Stop and call a licensed pro

  • Any gas smell, yellow flame, soot, or CO symptoms.
  • A relief valve streaming constantly, or banging pipes.
  • Water running dangerously hot at the taps.
  • Any actual repair, valve replacement or gas work.
Clean blue gas flame versus a yellow flame on a hot water system
A clean blue flame is healthy; a yellow or sooty flame is a stop-and-call sign.
Gas emergency

If you smell gas — what to do

A gas smell is an emergency. Do this, in order, and don't improvise.

1 · Don't ignite anythingNo switches, no flames, no appliances — a spark can ignite gas. Don't use your phone inside.
2 · Turn off the gasIf it's safe to reach, turn off the gas at the meter or bottle.
3 · Ventilate and leaveOpen doors and windows if you safely can, then get everyone outside into fresh air.
4 · Call for helpFrom outside, call your gas emergency line or a licensed gasfitter. Don't go back in until it's cleared.
When to call

When to call a licensed professional

Look and notice freely; leave touching and fixing to a licensed pro.

The rule of thumb is simple: looking and noticing is fine; touching, adjusting or repairing a gas, pressure or hot water component is a licensed job. Gas work in particular is licensed for good reason — carbon monoxide and gas leaks are genuinely dangerous, and a DIY attempt can make a safe situation unsafe.

If any of the warning signs above are present, book a repair with a licensed plumber or gasfitter, and keep your system on a regular service so the safety components — the TPR valve, the tempering valve, the burner — are checked before they become a problem.

See also: book a repair

Licensed plumber carrying out a hot water safety check in Sydney
A regular service checks the safety components before they become a problem.
FAQ

Hot water safety questions, answered

The questions we're asked most about hot water safety.

How do I know if my hot water system is safe?
Check for a clean blue gas flame (not yellow or sooty), a relief valve that only discharges while heating (not constantly), and hot water that's warm but not scalding. Any warning sign on these, or a gas smell, means stop and call a licensed professional.
Can a gas hot water system cause carbon monoxide?
Yes — a faulty or poorly ventilated gas system can produce carbon monoxide, which is colourless and odourless. Warning signs are a yellow or sooty flame, black marks around the unit, and headaches, nausea or dizziness when it's running. Treat these as an emergency and call a licensed gasfitter.
What should I do if I smell gas?
Don't ignite anything (no switches, flames or phones inside), turn off the gas at the meter if it's safe, ventilate and get everyone outside, then call your gas emergency line or a licensed gasfitter from outside. Don't go back in until it's cleared.
Why is my hot water suddenly scalding hot?
The tempering valve, which blends water down to a safe maximum of 50°C at your bathroom taps, may have failed. It's a safety risk — switch to cold at the tap and book a licensed plumber to replace it urgently.
Is it normal for the relief valve to drip?
A little discharge from the TPR valve's drain line while the system is heating is normal. Constant streaming, or the valve running non-stop, is a fault or a pressure problem and needs a licensed plumber.
What hot water safety checks can I do myself?
Only looking and noticing — flame colour, relief-valve behaviour, tap temperature, and keeping the area clear and ventilated. Any adjustment, valve replacement or gas work must be done by a licensed professional.
Worried about your system's safety?

Book a safety check

We'll inspect the gas, pressure and scald-protection components and put anything unsafe right — licensed, Sydney-wide, and we come to you.

Call 1300 096 668