No Hot Water? 9 Reasons Your System Has Stopped Working (and What to Do First)

Before you do anything

Cold shower at 6am is stressful — but most no-hot-water calls fall into 9 predictable causes. Some you can check safely in 60 seconds; others need a licensed plumber or gasfitter.

Safety first: if you smell gas, hear hissing near the unit, or see water pouring from a relief valve continuously, turn off the gas/water isolation valves and call 1800 GAS LEAK or J.O. Plumbing 24/7. Do not relight a gas heater that has tripped repeatedly.

The 9 most common causes

1. Pilot light out (older gas storage). Relight per the sticker — if it won't hold, the thermocouple is failing.

2. Tripped circuit breaker (electric/heat pump). Reset once; if it trips again, stop and call.

3. Off-peak hasn't kicked in. Electric units on tariff 31 only heat overnight — heavy daytime use empties the tank.

4. Failed heating element or thermostat. Element life is 5–10 years in Melbourne water.

5. Continuous flow unit fault code. Note the code on the controller before calling — it tells us the part to bring.

6. Gas supply issue. One appliance out can mean a regulator or meter issue.

7. Tempering valve seized. Common after 5+ years; lukewarm water everywhere is the giveaway.

8. Tank leaking from the base. The cylinder has rusted through — replacement only.

9. End of life. Gas storage 8–12 years, electric 8–15, heat pump 10–15, continuous flow 15–20.

What to check yourself (safely)

Is the isolator switch on? Has the breaker tripped?

Is the gas on at the meter and at the appliance?

Is there water dripping from the unit or the relief valve?

Is there a fault code on the controller? Photograph it.

When to call a plumber immediately

Water leaking from the cylinder body.

Gas smell, soot marks, or yellow flame on a gas unit.

Repeated breaker trips or fault codes.

Unit older than its expected lifespan and failing intermittently.

FAQ

Can you come out today?

Yes — J.O. Plumbing runs 24/7 emergency response across Melbourne.

Should I repair or replace?

If repair is more than 40% of replacement cost on a unit past two-thirds of its life, replace.

Call to action

Need help right now? Book online or call J.O. Plumbing 24/7 for upfront pricing and same-day service across Melbourne.