AC Water Leaking From Indoor Unit: Causes and DIY Checks Before Calling a Repair Service

The most likely cause first: a blocked drain

Dust, algae or debris build up inside the drain pipe over time, blocking the path condensation normally takes to drain outside. When it's blocked, water backs up and overflows from the indoor unit instead. This is the single most common cause of indoor leaking and often the easiest to fix.

DIY checks you can do before calling anyone

A few quick checks can sometimes save you a service visit, or at least tell the technician exactly what to look for.

• Check the drain pipe's outdoor end — make sure it isn't blocked, kinked, or submerged in standing water
• Check the air filter — a heavily clogged filter can cause the coil to ice up, and the melting ice is what actually overflows
• Look for ice on the indoor coil — if present, switch off cooling mode and let it melt before further checks
• Check if the indoor unit is level — a unit that has shifted slightly out of level can drain incorrectly even with a clear pipe

When it's not something you can fix yourself

If the drain pipe is clear, the filter is clean, and there's no visible ice, the cause is likely internal — a cracked drain pan (common in older units), an improperly sloped installation, or low refrigerant causing icing you can't see without opening the unit. These need a technician's inspection rather than a DIY fix.

Frequently asked questions