Complete fault finding guide for electric showers — RCD tripping, cold water, solenoid valve faults, element failure, flow switch issues, low pressure diagnosis, when to call an electrician vs plumber, and typical repair costs for 2026.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
Most electric shower faults fall into three groups. If it trips the RCD, the heating element has likely failed to earth and must be replaced. If it runs cold, the element has gone open-circuit, or the flow switch or solenoid valve is not activating the element. If there is no water flow, suspect low pressure or a blocked inlet filter. Isolate at the consumer unit and prove dead before any work; element, PCB and wiring faults are electrician-only.
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An electric shower heats cold mains water on demand as it flows over the heating element. Unlike mixer showers, electric showers do not use the stored hot water in a cylinder — they take cold water directly from the mains and heat it instantaneously. This makes them independent of the boiler or cylinder, but also means they require a large dedicated electrical circuit.
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Use the table below to narrow down the fault before you start. Match the symptom to the most likely cause, then jump to the relevant section. Anything involving the element, PCB, solenoid coil or wiring is electrician-only work — always isolate and prove dead first.
| Symptom | Most likely cause | Who to call |
|---|---|---|
| Trips the RCD on switch-on, every time | Element failed dead-short to earth | Electrician |
| Trips the RCD after a few minutes | Element insulation breaking down when hot | Electrician |
| Runs cold, water flows normally | Open-circuit element or flow switch not activating | Electrician |
| No water flow at all | Solenoid stuck closed, blocked inlet filter | Either |
| Weak / cold only at peak times | Low dynamic water pressure | Plumber |
| Drips from head after switch-off | Solenoid not closing or worn valve seat | Either |
| Clicks then goes cold | Thermal cut-out (TCO) operating | Electrician |
| Erratic temperature / dead unit | PCB failure | Electrician |
Never work on an electric shower without safe isolation
A 10.5kW electric shower draws approximately 46A at 230V. Contact with live conductors inside the shower unit will cause severe burns, cardiac arrest, or death. Always isolate at the consumer unit and prove dead before opening the unit.
The safe isolation procedure for an electric shower:
An electric shower that trips the RCD every time it is switched on — or during use — has a fault to earth. This is by far the most common serious fault in electric showers.
Interpreting the insulation resistance reading at a 500V DC test between each element terminal and earth:
| IR reading (element to earth) | Verdict | Action |
|---|---|---|
| Above 1 MΩ | Healthy | Look elsewhere for the fault |
| 0.5–1 MΩ | Degrading | Investigate; retest hot |
| Below 0.5 MΩ | Failing element | Replace element |
| Near zero | Dead short to earth | Replace element |
These thresholds are practical fault-finding guidance for a single appliance element, not a circuit insulation resistance acceptance value. For circuit insulation resistance minimums during inspection and testing, refer to insulation resistance testing.
The heating element is the most failure-prone component in an electric shower, typically lasting five to ten years depending on water hardness, usage frequency, and power rating. In hard water areas, limescale deposits on the element surface reduce heat transfer and cause the element to overheat, accelerating insulation breakdown — the same failure mode seen in immersion heater elements.
The solenoid valve is an electromagnetically operated valve that controls water flow into the heating chamber. Solenoid valve failure is a common cause of electric shower problems that do not involve the electrical supply circuit at all.
Solenoid replacement is a job for an electrician familiar with the specific shower model. The valve is accessible after safe isolation and removal of the shower cover. The water supply must be isolated at the isolating valve under the shower before replacing the valve body.
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The flow switch tells the shower's PCB that water is flowing and it is safe to energise the heating element. If water pressure is too low, the flow switch does not activate and the shower runs cold — this is a plumbing issue, not an electrical fault.
Understanding which trade to call for an electric shower fault saves time and cost. The fault can lie in the electrical side, the plumbing side, or — in many cases — both.
Repair costs for electric showers vary by fault type and shower model. Older models may have discontinued parts, making repair uneconomical. The figures below are indicative UK market guidance for 2026 — not a quote. Always get a price confirmed for your specific unit and circuit.
| Repair | Parts | Labour | Typical all-in |
|---|---|---|---|
| Heating element (most common) | £30–£60 | £50–£90 | £80–£150 |
| Solenoid valve | £20–£50 | £40–£70 | £60–£120 |
| PCB (model-dependent) | £80–£200 | £60–£100 | £140–£300 |
| New shower unit fitted | £150–£400 | £150–£300 | £300–£700 |
| New dedicated circuit | Cable, MCB/RCBO, RCD protection & certification | £200–£500 | |
Electric shower installation and replacement is notifiable work under Part P of the Building Regulations in England and Wales. Registration with NICEIC, NAPIT, or ELECSA allows you to self-certify the work and issue an Electrical Installation Certificate on completion. The certificate must be handed to the customer before you leave site.
The dedicated shower circuit must be designed for the unit's power rating. Approximate full-load current is the power rating divided by the nominal supply voltage (230V). The MCB or RCBO and cable must both be sized for that load and the installation conditions. Cable cross-sectional area depends on the installation method, grouping, ambient temperature and run length — verify against BS 7671 Table 4D5 (70°C thermoplastic flat twin-and-earth cable, the typical shower cable) and apply the relevant correction factors rather than relying on a rule of thumb.
| Shower rating | Approx. load at 230V | Typical protective device |
|---|---|---|
| 7.5 kW | ≈ 33 A | 40 A Type B |
| 8.5 kW | ≈ 37 A | 40 A Type B |
| 9.5 kW | ≈ 41 A | 45 A Type B |
| 10.5 kW | ≈ 46 A | 50 A Type B |
Device ratings shown are a common starting point; the final selection is the designer's and must satisfy overload and fault protection for the actual cable, length and installation method. Confirm the consumer unit can accommodate the load and that 30mA RCD additional protection is in place per Reg 701.411.3.3.
Use the Elec-Mate Electrical Installation Certificate app to complete and sign the EIC before leaving the property. Record test results, circuit details, and schedule of inspections directly on your phone. Instant PDF to the customer — no chasing paperwork later.
If the shower circuit has undersized cable or an unprotected circuit, quote the upgrade immediately using the Elec-Mate quoting app. Customers who receive a professional quote while you are present approve work at a significantly higher rate than those who receive a quote later by email.
When installing or replacing a shower in an older property, verify supplementary protective equipotential bonding under BS 7671 Reg 701.415.2 — the terminals of the protective conductor of each circuit supplying Class I and Class II equipment must be connected to accessible extraneous-conductive-parts in the room, including metallic service and waste pipes, metallic central heating pipework, and accessible metallic structural parts. This local supplementary bonding may be omitted only where the location's final circuits meet automatic disconnection, have 30mA RCD additional protection, and the extraneous-conductive-parts are effectively connected to the main protective bonding. Note that the A4:2026 AFDD requirement in Reg 421.1.7 applies to single-phase AC final circuits supplying socket-outlets rated up to 32A in specified building types (such as high-rise residential buildings, HMOs, purpose-built student accommodation and care homes) — a dedicated shower circuit is not a socket-outlet circuit, so 421.1.7 does not mandate an AFDD on the shower circuit itself.
Electric shower not working? Diagnose 8 common faults fast. Step-by-step guides for electricians. Get your shower back online today.
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