No hot water (electric storage system)
An electric storage hot water system has gone cold — no hot water at the taps. Usually the element, thermostat, supply, or (for off-peak) the tariff/timing.
Safety first
Hot water elements combine water and electricity — earth-leakage and scald risks. Isolate, prove dead, and never bypass earth-leakage protection. Tanks store very hot water.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
Failed heating element
Most likelyThe element has gone open circuit and no longer heats — the most common cause.
- 2
Faulty / tripped thermostat
#2The thermostat has failed, is set wrong, or a safety cut-out has tripped.
- 3
Off-peak / controlled-load not energising
#3Off-peak systems only heat during certain hours; a tariff/timer/contactor issue means it never gets power.
- 4
No supply / tripped protection
#4A tripped breaker/safety switch or lost supply leaves the system cold.
- 5
Element leaking to earth (tripping)
Least likelyA failing element leaks to earth and trips the protection.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModeCheck the hot water circuit's protective device and (for off-peak) whether it's within the heating window/controlled-load is active.
Protection on; controlled-load/off-peak energised when expected.
Supply/timing fine — check the thermostat and element.
Tripped protection or off-peak not energised — restore / chase the controlled-load.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
No hot water (electric)
→ step 2 - 2decision
Is protection on and (off-peak) energised in its window?
Yes→ step 3No→ step 4 - 3decision
Is the thermostat/cut-out healthy and calling?
Yes→ step 5No→ step 6 - 4result
Restore protection / chase the controlled-load (off-peak).
- 5decision
Is the element resistance sensible and insulation good?
Yes→ step 7No→ step 8 - 6result
Faulty/tripped thermostat or cut-out — find why, rectify.
- 7result
Re-check thermostat/supply/timing.
- 8result
Open element or low insulation — replace the element.
Common mistakes apprentices make
- Forgetting off-peak systems only heat in certain hours.
- Resetting a safety cut-out without finding why it tripped.
- Bypassing the safety switch when a leaking element trips it.
- Replacing the element without checking the thermostat/controlled-load.
When to stop & escalate
Hot water work is licensed electrical work (and tempering/valves may involve a plumber). A leaking element is a replacement — never run on defeated protection. Controlled-load/tariff issues may involve the supply authority/meter.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
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Related faults
Hot water runs out too quickly / not hot enough
There's some hot water but it runs out fast or never gets properly hot — often a partially-failed element, a thermostat set low, or a system being asked to do more than its size.
Off-peak / controlled-load hot water not heating
A controlled-load (off-peak) hot water system isn't being energised during its tariff window — the element and thermostat may be fine, but power never arrives at the right time.
Heater tripping the RCD / earth leakage
A heater circuit trips its RCD/earth-leakage protection — often when cold and first switched on, or once it's been damp — pointing to leakage to earth from the element.
Learn the theory
How the gear and circuits behind this fault actually work.