Electric Shower Keeps Tripping: Causes and Fixes
A shower that trips the RCD almost always has an earth-leakage fault — usually a failing heating element. Confirm leakage versus overload, then trace it methodically.
An electric shower is a heavy, wet load, which makes it a prime candidate for earth-leakage faults. When one repeatedly trips its RCD or RCBO, the odds strongly favour a failing heating element leaking to earth — but overloading and cable faults are worth ruling out too.
This guide explains how to distinguish a leakage trip from an overload, the common shower-specific faults, and how to confirm the diagnosis with a test rather than a guess. It assumes safe isolation before any investigation.
Key takeaways
- A shower tripping the RCD almost always means earth leakage, not overload.
- A failing (cracked or degraded) heating element leaking to earth is the classic cause.
- Test insulation resistance from line/neutral to earth to confirm element leakage.
- Overload trips (of the MCB/RCBO) point to a wrong-size cable or device, not leakage.
- Water ingress at the shower or its isolator can also cause leakage trips.
Leakage or overload?
First establish which protection is operating. If the RCD (or the RCD part of an RCBO) trips, you have an earth-leakage fault — current escaping to earth. If the overcurrent part trips (or a plain MCB), you have an overload or short-circuit, which on a shower usually means an undersized circuit or a wiring fault, not the shower itself.
The behaviour helps too: leakage often trips as soon as the shower runs, or when it switches between heat settings; overload tends to trip after the shower has been drawing full current for a while.
Isolate before testing
Prove the shower circuit dead with safe isolation and an approved voltage indicator before disconnecting the element or testing insulation resistance. It's a wet, high-current circuit — respect it.
The classic fault: a failing element
The heating element sits directly in the water path, so as it ages it can crack or degrade until the live element leaks current to earth through the water. That leakage trips the RCD. It often worsens over time — first an occasional trip, then every use — and may be worse on the hotter setting where more of the element is energised.
Confirm it by isolating and testing insulation resistance from line and neutral to earth at the shower with the element connected: a low reading points squarely at the element. Disconnecting the element and re-testing isolates it from the rest of the circuit.
Doing this on a job? Minor Works Certificate — part of TradePlanr. Free to start, no card needed.
Other shower-specific faults
Water ingress is the next suspect — a leaking shower unit, a failed seal, or moisture in the pull-cord isolator or its ceiling rose can all leak to earth. Inspect for damp, staining and corrosion around the unit and isolator.
Less commonly, a damaged supply cable (nicked during installation, or overheated on an undersized run) can leak or short. And an overload trip may reveal that the circuit was never correctly sized for the shower's kW rating in the first place — worth checking against the cable and device.
Certify the repair
After replacing the element or unit and re-testing, issue a Minor Works Certificate from TradePlanr with the insulation resistance and RCD results, so the customer has proof the shower is safe.
Confirming the fix
Once you've replaced the faulty element or unit, re-test: insulation resistance should be back to a healthy value, the RCD should hold under load, and the shower should run through all its settings without tripping. Record the readings so both you and the customer have evidence the fault is genuinely cleared, not just quiet for now.
From guidance to action
Frequently asked questions
Why does my electric shower trip the RCD?
Almost always because of an earth-leakage fault, most commonly a failing heating element leaking current to earth through the water. Water ingress at the unit or isolator is the next most likely cause.
How do I confirm it's the element?
Safely isolate, then test insulation resistance from line and neutral to earth at the shower with the element connected. A low reading points to element leakage; disconnecting the element and re-testing confirms it.
Could it be an overload rather than leakage?
If the overcurrent device trips rather than the RCD, yes — usually meaning the circuit was undersized for the shower's kW rating, or there's a wiring fault. Check the cable and device rating against the shower's design current.
Related guides
Electric Shower Installation
Cable sizing, protection, isolation and bathroom-zone rules for an electric shower circuit.
How to Price an Electric Shower Installation
The cable run to the board, not the shower unit, sets the price — how to survey, size and quote it.
Why Your RCBO Keeps Tripping
Work out whether it's overcurrent or earth leakage, then trace the fault by splitting the circuit.
