AC Leaking Water in Phoenix: The Clogged Drain Problem and How to Fix It

For nine months of the year, Valley air is dry and the AC produces very little condensate. When monsoon humidity arrives in July, the same system suddenly pulls gallons of water a day off the coil. A drain line that was fine when it barely carried water clogs with dust, algae, and mineral scale the moment real flow starts.

Attic air handlers, common in two-story Valley homes, are the ones that cause ceiling damage. The secondary drain pan under the unit is supposed to catch overflow, but if it's rusted, cracked, or its float switch isn't wired, the water goes into the drywall below.

Rooftop package units drain onto the roof, so a clog shows up as water running down the outside of the house or pooling in a roof valley rather than inside. Less damaging, but it still means the drain is blocked.

Turn cooling off. Find the condensate drain line where it exits outside, usually a white PVC pipe near the air handler wall or under the eave. Fit a wet/dry vacuum over the end and run it for two to three minutes. A clog often comes out as a slug of gray sludge.

Inside, look for a capped tee on the drain line near the air handler. Pouring a cup of white vinegar down it monthly during summer keeps algae from rebuilding. Skip bleach; it corrodes some drain fittings and coils.

If the float switch tripped and shut the system down, clearing the line and letting the pan drain will usually restore power. If the system was frozen, let it thaw fully before restarting or the drain will flood again.

Call a pro if water keeps appearing after you've cleared the line, if the drain pan is rusted through or cracked, if the leak is coming from the coil housing rather than the pan, or if there's any ceiling staining. Water damage in an attic escalates fast in summer heat.

A tech will flush the line with pressure or nitrogen, verify the slope of the drain, check the pan and float switch, and confirm the coil isn't freezing. It's typically a same-day, under-an-hour repair.

PhoenixCoolQuotes connects you with licensed local HVAC contractors who handle drain problems every monsoon. We're a free matching service, not the contractor.