Sparks When Plugging Something In

What's happening?

When you push a plug into a socket that is already switched on, current starts to flow the instant the pins touch. Chargers, laptops, TVs and anything with a power supply draw a short surge at that moment, so a very small blue flash at the pin is possible and does no harm if it is rare, quiet and leaves no trace. It is avoidable: switch the socket off, plug in, then switch on. What is not normal is a spark you hear as a crack or bang, an orange or yellow flash, a spark with the socket switched off, one that happens with every appliance, or any black or brown mark on the pins or the socket face. Those point to worn socket contacts, a loose terminal behind the faceplate, or a fault in the appliance or its plug. If the spark comes when you flick the socket switch rather than when you insert the plug, see the page on a plug sparking when switched on.

What usually causes it?

• Normal start-up surge from a charger or power supply when plugged into a live, switched-on socket
• Worn or loose socket contacts that make intermittent contact with the pins
• A loose terminal screw behind the socket faceplate
• A damaged appliance plug, bent pins or a loose fuse inside the plug
• A fault in the appliance drawing far more current than it should at switch-on
• A socket switch that no longer breaks the supply, so the socket stays live when off

Is it dangerous?

One tiny flash with the socket switched on is not a hazard in itself. Repeated sparking, a loud crack, a spark with the socket switched off, or any blackening is a fault that can overheat the socket and start a fire. Electrical Safety First lists burn marks, arcing sounds, blowing fuses and tripping breakers as signs to get a registered electrician in. If the socket smokes or the plastic melts, switch off at the consumer unit and call 999 if anything is alight.

Can I fix it myself?

1. Switch the socket off before plugging in or unplugging. If the spark stops, it was the start-up surge. 2. Try the same appliance in a different socket. If it sparks everywhere, the appliance or its plug is the problem: stop using it and check it against the product recall list. 3. Try a different appliance in the same socket. If that sparks too, the socket is the problem: stop using it. 4. Look for black or brown marks on the pins and around the socket holes. 5. Do not open the socket or plug up the holes. Leave the socket unused until it has been checked.

When should you call an electrician?

Call an electrician if the socket sparks with more than one appliance, sparks while switched off, has scorch marks, feels warm, crackles, or trips the circuit when you plug in. Book urgently (same day) if you see melting or smell burning. A spark that only ever happens with one appliance points to the appliance, which may need an appliance repair engineer or replacing instead.

What will the electrician actually do?

• Isolate the circuit and inspect the socket contacts, terminals and back box
• Tighten or re-terminate loose conductors and cut back any heat-damaged cable
• Replace the socket if the contacts are worn or the switch no longer isolates
• Test the circuit for polarity, earth continuity and insulation resistance
• Check the appliance plug and fuse, and advise if the appliance itself is at fault

Who fixes this

• Electrical fault finding

What it usually costs

Electrical Fault Finding Cost

Priced on survey

Questions people ask

Sources & References

1. Electrical Safety First: Your questions answered (burn marks, arcing, when to call an electrician)
2. Electrical Safety First: Plugs and fuses
3. Electrical Safety First: Product recalls
4. BS 7671: IET Wiring Regulations (18th Edition)