Electrics trip when it rains: outside lights and garden sockets

It rains, and the house goes dark. It dries up, and everything works again. This pattern is one of the clearest clues an electrician can get. Water is getting into part of your installation, and your RCD is doing exactly what it should.

Why rain trips the electrics

An RCD (residual current device) watches for current escaping from a circuit, usually to earth. Rainwater carries current. When water gets inside an outside light, a garden socket or a damaged cable, a small amount of current leaks through it. If the leak is big enough, the RCD trips.

When the fitting dries out, the leak stops. That is why the fault seems to come and go.

The usual suspects

Where	What goes wrong
Outside wall lights	Seals perish, glass cracks, water collects inside
PIR security lights	Sensor housings let water in; cable entry at the top acts as a funnel
Garden sockets	Covers left open, broken flaps, water in the back box
Lights set into decking or paths	Water pools around them; seals fail
Shed, garage or garden office supply	Cable damaged by digging, rodents or age; wet connections at the outbuilding
Pond pumps and fountains	Leaky pumps or connections near water
Extension leads run outside	Indoor leads left out in the garden
Cables clipped along fences	UV damage cracks the outer sheath over time

A common one in London is a security light fitted with its cable coming in from the top. Water runs down the cable and straight into the fitting.

What you can check safely

1. Note which switch trips. Is it the RCD covering the outside lights, or the sockets?
2. Turn off the outside lights at their switch, then reset the RCD. If it holds while the lights are off, the lights are the likely cause.
3. Unplug anything outside. Pond pumps, garden tools and leads. Reset again.
4. Look, don’t touch. From a distance, check outside fittings for condensation inside, broken covers or missing seals.
5. Think about recent digging. New fence posts, planting or paving can damage a buried cable.

Do not open outside fittings or touch wet electrical equipment. If a fitting is damaged and live, keep people and pets away from it.

Why Bromley gardens see this a lot

Bromley is London’s largest borough by area, and its homes have more outside space than most. Figures from the VOA council tax stock of properties show that 14.4% of homes in Bromley are detached houses, the highest share of the boroughs we cover, against 3.5% across London. Another 23.8% are semis and 5.3% are bungalows.

That means long back gardens in Petts Wood, Orpington and West Wickham, and large plots in Chislehurst and Keston. Bigger gardens tend to have:

• garden offices, workshops and sheds with their own supply
• long buried cables to outbuildings, sometimes laid decades ago
• outside lighting along paths and drives
• pond pumps and garden sockets far from the house
• detached garages fed by a separate cable, known as a submain

Each of these is a place for water to get in. A cable to a shed buried too shallow, or without the right protection, can be damaged by a spade years later. The trip may only start when the damaged section gets wet.

How an electrician tracks it down

Rain related faults can be tricky because the fault may not be there when the electrician arrives on a dry day. Our electrics keep tripping visits usually involve:

1. Asking which circuits trip and in what weather.
2. Testing insulation on each outside circuit. Damaged cable often shows lower readings even when dry.
3. Opening and inspecting outside fittings and garden sockets.
4. Testing the cable to outbuildings section by section.
5. Replacing failed fittings with ones rated for outdoor use, and resealing cable entries from below.
6. Checking that outside sockets and circuits have RCD protection.

If you can, take a photo of the consumer unit after each trip and note the weather. If the fault only shows after heavy rain, an electrician may suggest coming back in wet weather to catch it.

Getting outside electrics right

The current wiring standard is BS 7671:2018+A4:2026, which since 15 October 2026 is the only version electricians should work to. Good outdoor work generally means:

• fittings with a suitable weather rating, fitted the right way up
• cable entries from below, not above
• RCD protection for outside circuits and sockets
• buried cable at a suitable depth, protected and marked
• a proper supply to outbuildings, not an extension lead through a window

A new circuit to a garden office or outbuilding is notifiable work under Part P of the Building Regulations. It must be done by a registered competent person who can self certify, or notified to building control. The Planning Portal explains the options. Ask to see the electrician’s scheme registration and check it.

When it is more than the garden

If trips happen in rain but you have no outside electrics, look up. Water through a roof, a blocked gutter overflowing into a wall, or a leak around a loft light can all cause rain related trips. Read our guide to water leaking through a light fitting if you see drips or stains near a ceiling light.

If the RCD trips at night and the weather is dry, the cause may be something on a timer instead. See RCD keeps tripping at night.

For homes in Bromley and across south east London, the first test is simple. Switch off the outside lights, unplug the garden, and see whether the RCD holds.