Mira Electric Shower Problems (Mira Sport, Mira Atom)
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Post a job — we'll find you an engineer →Isolate at the consumer unit and verify dead with a voltage tester before touching any internal components. Mira Sport units are 7.2–10.8 kW and will be on a dedicated high-current circuit.
Mira electric showers are reliable workhorses in thousands of British homes, but like any high-powered appliance, they can develop faults—usually signalled by a complete loss of power, no hot water, weak flow, or the unit cutting out mid-shower. Most problems stem from three culprits: a tripped circuit breaker at the consumer unit, a failed heating element, or limescale buildup in hard-water areas. This guide walks you through diagnosis and repair for the most common Mira Sport and Mira Atom faults, from checking your electrics to replacing components yourself. If you spot an earth fault, persistent tripping, or are uncomfortable working with high-current circuits, it's worth calling a qualified electrician or Gas Safe engineer to avoid safety risks.
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Most likely cause & what to check
Establish your model and generation. The Mira Sport has been sold since 1990 and has gone through multiple revisions — Sport, Sport Max, Sport Thermostatic, and the current Sport with Eco-mode. The Mira Atom (introduced around 2005) is a more compact unit aimed at smaller bathrooms. Check the label inside the cover for the precise model code and kW rating. Mira's full parts catalogue is searchable at mirashowers.co.uk and Mira also runs a dedicated spares line: 01242 221221 (Mon–Fri, 8 am–5 pm).
If the shower has no power or does not respond, check the consumer unit first. Mira Sport units require a dedicated 45 A double-pole isolator within sight of the shower. A tripped RCD or MCB is the most common cause of complete failure. Reset the breaker and test — if it trips immediately under load, there is likely an earth fault in the heating element or wiring, which will require a qualified electrician. If the isolator is on but there is still no power to the unit, use a multimeter to check for voltage at the terminal block inside the cover (take care — only test live terminals if you are a competent person).
No hot water / runs cold: the most likely cause is a failed heating element. Inside a Mira Sport, the element is a stainless steel or copper canister type. Isolate, remove the cover (four screws), and with a multimeter on resistance, measure across the element terminals. A working 9 kW element reads approximately 5.3 Ω. An open-circuit reading means the element is dead. Mira Sport elements are available from Screwfix (search "Mira Sport element"), Toolstation, or Plumb Center, typically £30–£50 depending on kW. The element unscrews anti-clockwise — always fit new PTFE tape on the thread. The Mira Atom uses a different, smaller element (check mirashowers.co.uk for exact part numbers).
No water or weak flow with power present: the solenoid valve has failed or is blocked by limescale. On the Mira Sport, turn off the water supply, remove the inlet connection, and pull out the solenoid coil. The rubber diaphragm inside degrades over time, especially in hard-water areas. Soak the valve body in descaler for 20–30 minutes. Replacement solenoid diaphragm kits for the Mira Sport are sold by Mira as a service kit (around £8–£12). If the coil itself has failed (check with a multimeter — a healthy coil reads 3–7 kΩ), replace the full solenoid assembly.
Thermal cut-out (TCO) tripping: the Sport has a manual-reset TCO that trips when the water temperature inside the heater exceeds a safe threshold. This is usually caused by blocked inlet filter, heavy limescale on the element, or low mains water pressure. Locate the reset button inside the cover (it is typically orange on the Sport, red on older variants) and press it firmly. Clean the inlet filter screen by removing it from the inlet fitting and rinsing under the tap. In hard-water areas (anything above 200 ppm — check your local water company's website), descale annually by running a dilute limescale remover solution through the unit.
Mira Atom-specific fault — intermittent cutting out: the Atom has a known sensitivity to fluctuating water pressure; if the incoming cold pressure drops below about 1.0 bar (common in older properties during peak demand), the pressure switch can cause the unit to cut out mid-shower. Fitting a pressure-reducing valve upstream to give a stable 1.5–2 bar can cure this. If the Atom is under two years old, faults are covered by Mira's two-year guarantee — register at mirashowers.co.uk or call 01242 221221. Out-of-warranty PCB replacements are rarely economical; a new Atom costs around £120 from Screwfix.
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Frequently asked questions
Why has my Mira shower suddenly stopped working completely?
The first thing to check is your consumer unit—a tripped RCD or MCB is the most common culprit. Reset the breaker and see if it holds; if it trips again immediately, you likely have an earth fault and should contact a qualified electrician. If the breaker stays on but the shower still has no power, use a multimeter to test for voltage at the terminal block inside the shower cover.
My Mira shower runs cold but the power is on—what's wrong?
The heating element has almost certainly failed. Isolate the unit, remove the cover, and test the element with a multimeter on resistance mode; a reading that's open-circuit (infinite) confirms it's dead. Replacement elements are inexpensive (£30–£50) and unscrew anti-clockwise—always use fresh PTFE tape when refitting.
What does it mean when the orange button inside the cover keeps popping out?
That's the thermal cut-out (TCO) doing its job—it trips when water inside the heater gets too hot, usually because of a blocked inlet filter or heavy limescale. Clean the inlet filter screen and press the orange button to reset; in hard-water areas, descale the unit annually with a limescale remover to prevent repeated trips.
My Mira Atom keeps cutting out during my shower—is it broken?
The Atom is sensitive to low incoming water pressure; if your mains pressure drops below 1.0 bar (common in older properties at peak times), the pressure switch will cut out. Fitting a pressure-reducing valve upstream to stabilise pressure at 1.5–2 bar often fixes it, or contact Mira on 01242 221221 if the unit is under two years old and still under warranty.