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uk Home & property emergencies indoor ac leaking water • air con dripping water • ac unit dripping indoors • split ac indoor unit leak • wall mounted ac leaking • air conditioner water leak • condensate leak air con • ac started leaking suddenly • water dripping from ac • ac leak onto wall • ac leak onto floor • ac leaking near electrics • unexpected water from air con • indoor unit dripping overnight • ac leak after heavy use • air con overflow • dripping cassette unit • dripping mini split • ceiling drip from ac unit

What to do if…
an indoor air-conditioning unit starts dripping water or leaking unexpectedly

Short answer

Turn the air-conditioning off (and isolate power if you can do so safely), then keep water away from electrics and contain the leak while you arrange a qualified engineer.

Do not do these things

  • Don’t keep running the unit “to see if it stops” — leaks can quickly damage walls, ceilings, floors, and electrics.
  • Don’t open the indoor unit casing or poke inside it while it’s powered.
  • Don’t put towels or a bucket where water could run onto plugs, extension leads, sockets, or the consumer unit.
  • Don’t try to “top up” refrigerant or touch pipework/refrigerant components yourself.
  • Don’t ignore wet plasterboard, carpet/underlay, or skirting — lingering moisture can cause further damage and mould.

What to do now

  1. Switch the system off at the controller/remote. If water is dripping near electrics or you feel unsure, isolate power at the local AC isolator switch (if fitted) or at the relevant circuit at the consumer unit only if you can do it safely (dry hands, dry floor).
  2. Stop water reaching electricity. Unplug nearby devices if safe. Move extension leads/power strips up and away from the wet area.
  3. Catch and contain the water. Put a bucket/tray under the drip line and place towels around it. If the leak is from above/inside a wall, protect flooring with a plastic sheet or bin liners under towels.
  4. Reduce spread and damage for the next hour.
    • If water is running down a wall, gently tape a strip of plastic to guide drips into a container.
    • Wipe up standing water promptly.
  5. Only do homeowner-safe checks (no tools, no panels):
    • If you can see the condensate drain pipe where it exits the building, check for an obvious kink or disconnection (from the outside only, if safe).
    • If your user manual clearly describes removing/cleaning a filter as a homeowner task, and you can do it without opening panels or using tools, you can check whether it’s heavily clogged and set it aside to dry. If you’re unsure, skip this and wait for an engineer.
  6. Arrange the right help.
    • If you rent: contact your landlord/letting agent immediately, explain there is active water leakage, and ask for an air-conditioning engineer.
    • If you own: book a reputable air-conditioning engineer. If the system contains refrigerant (most fixed split systems do), the company and personnel working on it should have the appropriate F-gas certification/qualifications.
  7. Document the situation quickly. Take a few photos/videos of the dripping, the surrounding damage, and the unit model/serial label (without opening panels). This helps the engineer and can help with insurance/landlord records.
  8. If there’s significant water or ceiling bulging: keep people out of that spot, place containers underneath, and consider calling an emergency property maintenance service if you cannot stop the leak and damage is escalating.

What can wait

  • You don’t need to diagnose the exact cause right now.
  • You don’t need to dismantle the unit, flush lines, or attempt internal cleaning in a panic.
  • You don’t need to decide about replacement today — focus on stopping water damage and getting it inspected.

Important reassurance

A sudden indoor AC leak is common and often relates to drainage or airflow issues rather than something “catastrophic.” Turning it off and keeping water away from electrics is a safe, effective first response.

Scope note

This is first steps only — an engineer may need to inspect drainage, insulation, pipework, the condensate pump (if fitted), and any coil/refrigerant-related issues.

Important note

This is general information, not professional electrical or engineering advice. If you cannot safely isolate power or water is reaching electrical points, prioritise safety and get qualified help.

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