Condensate Leak in the Attic in Los Altos, CA

Condensate Leak in the Attic in Los Altos

When the AC runs, the coil pulls moisture out of the air, it collects in a pan, and a drain line carries it off. Clog that line and the pan overflows, and on an attic install the water comes straight down through the ceiling. The first sign in most Los Altos homes is a stain, sometimes a soft patch in the drywall, not a sound.

A lot of the housing here is single-story ranch with a wide footprint, and those plans often run dual-zone systems with two air handlers. That's two coils making condensate and two drains to keep clear, frequently tucked into attic space. The good news is that a leak like this is almost always one fixable part rather than a failing system. Usually a plugged drain line, a float switch that never cut the AC, a worn condensate pump, or a pan that's cracked or pitched wrong.

Plenty of these ranches have been remodeled or added onto over the years, and HVAC moved or extended during a remodel doesn't always get the same care as the original. A condensate drain routed quickly during an addition is the kind that loses its slope or skips a float switch. The emergency pan and that switch under the air handler are the last line before the ceiling, so we confirm they're actually there and working.

Common causes

Clogged primary condensate line. Algae and sludge build inside the drain and block it, so the pan backs up and overflows. We clear it with a wet vacuum from the termination, flush the line, and run water through the pan to confirm it drains. We add a cleanout tee where one is missing so the line stays serviceable.

Float switch that didn't cut the system. The safety float should shut the AC off when water rises in the pan, but a stuck, missing, or miswired switch lets it keep running and overflowing. We test it by lifting the float and watching the system shut down, and install one where an attic unit has no protection.

Failed condensate pump. Where an attic air handler sits below its drain exit, a small pump lifts the water out. A burned motor or a stuck float means the reservoir overflows. We power-test the pump, check its check-valve, and replace it if it won't reliably clear its tank.

Improper pan slope after a remodel. When an air handler is moved or re-set during a remodel, it isn't always left sitting level toward the drain, so water pools and spills instead of running off. We check the pan's pitch and shim the air handler so it drains to the fitting, and verify the drain line keeps its downhill slope.

Cracked or corroded primary pan. An aging pan can crack or rust through and leak straight to the ceiling even with a clear drain. We inspect it with a light and mirror, confirm it holds water, and replace any pan that's failed.

How we diagnose it

On a dual-zone home, confirm which of the two air handlers is overflowing.
Pour water through the primary pan to separate a clog from a cracked or mis-sloped pan.
Test the float switch by lifting the float and confirming the system shuts off.
Clear and flush the primary drain line and verify flow at the termination.
Inspect both pans for standing water and check the condensate pump under power where present.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

Condensate Leak in the Attic in Los Altos: common questions

Are you local to Los Altos or coming from across the Bay?

We're based in San Ramon and run the whole Bay Area, Los Altos included. We route by the day's South Bay calls, so you'll get a real arrival window when you call rather than an all-day promise. A ceiling stain that's still spreading gets treated as same-day where the schedule allows.

My system is dual-zone. Does that make the leak harder to fix?

Not harder, just a matter of finding the right unit first. With two air handlers we confirm which one is overflowing before we open anything, then fix that drain or pan. The second system stays untouched unless its drain is heading the same way, in which case we'll note it on the estimate so you can decide.

The leak started after we remodeled. Is that related?

It can be. HVAC that gets moved or re-run during a remodel sometimes ends up with a condensate drain routed quickly, with marginal slope or no float switch. If your air handler moved or the drain was re-run during the work, that's the first place we look. We check the slope and the safety switch along with the clog.

Nearby and related

Condensate Leak in the Attic near Los Altos: Palo Alto · Mountain View · Cupertino .

This is usually a ac repair in Los Altos job. See our ac repair overview or the Los Altos service area.