What fails a PAT test? The most common failures
Most failures are visible before any instrument comes out
The formal test has two halves: a visual inspection and instrument tests. In practice the visual inspection catches the majority of failures — damaged cables and flexes, cracked or taped-up plugs, scorch marks around pins, bent earth pins, strained cable grips where the flex pulls out of the plug, and casings held together with hope.
This is good news: it means a member of staff doing informal visual checks between test visits can catch most developing hazards early, for free.
What the instruments catch
Earth continuity failures: Class I appliances (kettles, toasters, most white goods — anything metal-cased) rely on an earth path to make a fault safe. A broken earth conductor is invisible from outside and turns a minor internal fault into a live metal case.
Insulation resistance failures: the insulation separating live parts from the parts you touch degrades with heat, age, and abuse. The test applies a voltage and measures leakage — failures here mean the appliance is one step from delivering a shock.
Polarity and wiring faults: mostly found in rewireable plugs and extension leads that someone has wired incorrectly — live and neutral swapped, or the earth connected to nothing.
The serial offenders
Extension leads and multiway adaptors fail more than any other item — they are trodden on, daisy-chained, overloaded, and forgotten. Kettles and toasters suffer heat-degraded flexes. Power tools and site equipment take mechanical abuse. And user-supplied phone chargers, especially cheap unbranded ones, are a recurring hazard in HMOs and staff areas.
What happens when something fails
A failed item is labelled, taken out of service, and recorded in your register with the reason. Some failures are economically repairable — a new plug, a replaced flex — and can be retested on the spot or at the next visit. Others (failed insulation on a £15 kettle) are replacements. Either way the paper trail shows the hazard was found and dealt with, which is precisely the record your insurer wants to see.
Quick answers
What failure rate should I expect?
It varies hugely with environment and how recently things were last tested. Well-maintained offices often see low single-digit percentages; first-time tests in older or harsher premises find more. A high failure rate on a first visit usually drops sharply once bad extension leads and damaged flexes are cleared out.
Can a failed appliance be fixed?
Often, yes — plugs, fuses, and flexes are cheap repairs. The tester records the failure reason so you know whether repair or replacement makes sense.
Does a pass guarantee the appliance is safe forever?
No — a pass records that the appliance was safe at the time of the test. That is why intervals matter and why visual checks between visits are worth doing.
Relevant services & areas
Booking or compliance questions for your premises? These pages go deeper on what we test locally.
Local service areas
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