PanicStation.org
UK USA
us Home & property emergencies furnace leaking water • dripping furnace • furnace leak getting worse • water around furnace • puddle near furnace • hvac leaking water • air handler dripping water • condensate drain overflow • condensate pump leaking • humidifier leaking furnace • water near furnace electrical • basement furnace water leak • boiler leaking water • hydronic boiler leak • heater leaking water • hvac emergency water leak • renting furnace leaking • landlord hvac repair urgent • gas smell near furnace • carbon monoxide alarm sounding

What to do if…
your boiler or furnace is dripping water and the leak seems to be getting worse

Short answer

Shut the system off and keep water away from electrical hazards, then call a licensed HVAC technician or plumber (and your landlord/property manager if you rent).

Do not do these things

  • Do not keep running the furnace/boiler “to see if it stops.”
  • Do not open sealed panels or put your hands inside the unit.
  • Do not touch outlets, cords, breakers, thermostats, or the unit’s power switch if you’re wet or standing in water.
  • Do not ignore a gas-leak smell (often described as “rotten eggs”) or a carbon monoxide alarm.

What to do now

  1. Turn the system off.
    • Set the thermostat to OFF.
    • If you can safely access it, turn off the furnace/boiler service switch (often a light-switch style switch near the unit).
    • If water is spreading or you’re unsure, shut off power to the HVAC at the circuit breaker (only if you’re not standing in water and the area is dry enough to do this safely).
  2. If you smell gas or a CO alarm is sounding:
    • Leave the building immediately and get to fresh air.
    • Do not use switches, lighters, or anything that could spark. Avoid using a phone inside the building.
    • From outside (or a neighbor’s location), call 911 and/or your gas utility’s emergency number. Do not re-enter until responders say it’s safe.
  3. Stop more water from feeding the leak (only if it’s obvious and you can do it safely).
    • If your furnace has a whole-home humidifier, turn off its water supply valve (often on a small copper/plastic line).
    • If you have a hot-water boiler and you can clearly identify the cold-water feed valve to the boiler, you can close it to limit further water entry (don’t force stuck valves).
  4. Limit damage while staying safe.
    • Put a shallow pan/bucket under the drip and towels around it.
    • Mop up water promptly so it doesn’t reach outlets, extension cords, or stored items.
    • Keep kids/pets away from the wet area.
  5. Call for urgent service and use the right words.
    • Tell the company: “active water leak at furnace/air handler/boiler, getting worse; system is shut off; water is near (outlet/breaker/pump/etc.).”
    • If you rent: notify your landlord/property manager immediately and document that you shut the system off to prevent damage.
  6. Document quickly (helps the repair go faster).
    • Photo/video of where the water is coming from and any pooling.
    • Note whether the unit is high-efficiency (often has white PVC venting), has a humidifier, or whether this started after heavy A/C use or a temperature swing.

What can wait

  • You do not need to figure out the exact cause (clogged condensate drain, pump failure, humidifier line leak, boiler feed/relief issues) before calling.
  • You do not need to flush lines, use chemicals, or remove panels right now.
  • You do not need to decide on major replacement today.

Important reassurance

A worsening HVAC/boiler water leak is common enough that technicians see it often, and many causes are repairable. Turning the system off and preventing electrical contact are the most protective first steps.

Scope note

This guide is for stabilising the situation and reducing risk. A licensed professional still needs to inspect, fix the leak source, and confirm safe operation.

Important note

This is general safety information, not a diagnosis. If there’s any gas smell, a CO alarm, or water near electrical components, treat it as urgent and get professional help.

Additional Resources
Support us