Condensate Leak in the Attic in Sunnyvale, CA

Condensate Leak in the Attic in Sunnyvale

Sunnyvale is one of the warmer South Bay microclimates, and a lot of the older ranch stock has the air handler tucked up in the attic to free up floor space. Those two facts together are why we get condensate-leak calls here every cooling season. When the AC runs, the evaporator coil pulls moisture out of the air and that water has to drain somewhere. On an attic install it travels through a PVC line, often across a long lazy run with a trap, and out to a termination. The moment that line slows down, water backs up into the pan and finds the path of least resistance, which is your ceiling.

The good news is that this is almost never a dead system. A ceiling stain looks alarming, but the equipment under it is usually fine. The failure is in the drainage path: a clogged primary line, a pan that has rusted or cracked, a float switch that should have shut the system off and didn't, or a slope that was wrong from the day it was installed. Every one of those is a part or a correction, not a replacement.

We see this more on the 1960s tract homes where the air handler is original or has been swapped without anyone re-checking the drain pitch. On the newer Lawrence Station and Heritage District builds the drainage tends to be cleaner, but a clog can still happen on any system after enough summers of algae growth in the line.

Common causes

Clogged primary condensate line. This is the one we find most. Algae and biofilm build up inside the PVC over a few cooling seasons and the line stops draining. Water backs into the primary pan and overflows. We clear the line with a wet vac at the termination and flush it, then confirm it runs free. If there's no access tee to service it, we add one so the next cleaning is a five-minute job.

Failed or missing float switch. The float switch sits in the pan or on the drain and is supposed to cut the system off before water ever reaches the ceiling. When one is wired wrong, stuck, or was never installed, the AC keeps running and overflowing. We test it by lifting the float and confirming the system shuts down. If it's bad or absent, we install a proper safety float on the primary drain.

Cracked or rusted primary drain pan. On older attic air handlers the metal pan under the coil corrodes, or a plastic pan cracks, and water leaks straight through regardless of whether the line is clear. We inspect the pan with a flashlight and a moisture check. A cracked pan means pulling the coil to replace it, which we put on the written estimate before we touch anything.

Improper drain slope. A condensate line needs continuous downhill pitch, roughly a quarter inch per foot. On attic runs that get bumped, sag between supports, or were installed flat, water pools and overflows even when the line is clear. We check the run with a level and re-support or re-pitch it so it drains by gravity the way it should.

Plugged or overflowing emergency pan. Attic installs should have a secondary emergency pan under the unit with its own drain. When the primary fails and the emergency pan is also clogged or has no working drain, the backstop is gone and the water reaches the ceiling. We clear the emergency drain, confirm it daylights somewhere visible, and tie its float switch into the safety circuit.

Condensate pump failure. Some Sunnyvale attic and closet conversions can't drain by gravity, so the water goes to a small condensate pump. When the pump's float sticks or the motor dies, the reservoir fills and spills. We test the pump by filling the reservoir and watching it cycle. A failed pump gets replaced, and we add a safety float that kills the AC if the new pump ever quits.

How we diagnose it

Pull the access panel and inspect the primary pan and coil for standing water, rust, or cracks with a light and a moisture meter.
Test the float switch by lifting it to confirm the system actually shuts off, and verify it's wired into the control circuit.
Flush and wet-vac the primary line, then watch it drain to confirm the clog is gone and not merely shifted.
Check the drain pitch with a level along the full attic run and look for sags or flat sections between supports.
Confirm the emergency pan has a clear drain and a working secondary float as the last line before the ceiling.

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

Condensate Leak in the Attic in Sunnyvale: common questions

Do you cover Sunnyvale, or are you mostly an East Bay company?

We work the South Bay including Sunnyvale, Mountain View, Santa Clara, and Cupertino out of our San Ramon base. A ceiling leak is one we try to get to same-day when we can, because every hour the system keeps running is more water in the drywall. Call (925) 999-4095 and we'll tell you honestly when we can be there.

Sunnyvale runs hot in summer. Does that make condensate problems worse?

Yes. The harder and longer your AC runs through July and August, the more condensate the coil produces, so a marginal drain line that limped along in a cooler town overflows here. Heavy cooling duty also feeds the algae growth that clogs the line in the first place. A summer flush is cheap insurance on an attic system in this climate.

There's a water stain on my ceiling but the drip stopped. Is it fixed?

Probably not. A line that clogs intermittently will drain enough to stop the drip, then back up again next time the AC runs a long cycle. The stain means the pan overflowed at least once, which usually means the float switch didn't do its job. We'd want to clear the line and test that safety so the next overflow doesn't reach the ceiling.

Nearby and related

Condensate Leak in the Attic near Sunnyvale: Mountain View · Santa Clara · Cupertino .

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