Condensate Leak in the Attic in Portola Valley

Condensate Leak in the Attic in Portola Valley

An air conditioner pulls moisture out of the air as it runs and drops that water into a pan under the evaporator coil. The water leaves through a primary condensate line, and when the line clogs, it has nowhere to go but over the pan's edge. In an attic install here, the first thing anyone notices is usually a stain spreading on the ceiling, sometimes a soft patch in the drywall before there's an actual drip.

Portola Valley's original Eichler-influenced homes in the Ladera-adjacent pockets were mostly slab-on-grade with no attic to speak of, so attic AC installs here tend to be additions and outbuildings built onto those footprints, along with the larger custom homes on wooded acreage that were built with attics from the start. Either way, the oak-and-redwood hill air holds enough moisture that the coil makes steady condensate, and the drain line grows biological slime over a season or two that eventually blocks it.

On the ranch properties toward Skyline and the wooded lots off Alpine Road, drain lines were often routed a long way to reach an exterior wall, and a line pitched wrong at install will pool and back up no matter how clean it is. We trace the leak to the specific cause, whether it's the line, the pan, or the float switch, rather than guessing.

Common causes

Clogged primary condensate line. Algae and slime build up inside the drain over time and block it, so water backs up into the pan and spills over. We clear the line with a wet vacuum at the termination, flush it, and pour water through the pan to confirm it drains clean. Where there's no cleanout on the line, we point out where one belongs.

Float switch that never tripped. The safety float in the pan or drain line is supposed to cut the AC off before water rises over the edge. When it's missing, miswired, or stuck, the system keeps running and keeps making water until it overflows. We lift the float to confirm the system actually shuts down, and install one where an attic unit doesn't have one.

Failed condensate pump. Units in an addition or outbuilding that sit below their drain exit often rely on a small pump to lift water out to daylight. When the pump motor fails or its own float sticks, the reservoir overflows. We test it under power, check the check valve, and replace the unit if it won't reliably clear its tank.

Cracked or rusted primary pan. An aging pan can crack or corrode through, letting water reach the ceiling even with a completely clear drain. We inspect it with a flashlight and mirror and confirm it actually holds water rather than just looking at it from below. A cracked pan gets replaced, not patched.

Improper pan slope from the original install. If the air handler sits level or tips the wrong direction, water pools at the low corner instead of reaching the drain fitting. On the sloped, wooded lots common here, we check both the pan's pitch and the full line's grade, since a long run losing its downhill slope partway will back up just as badly as a clog.

Emergency drain pan filling up. The secondary pan is the last barrier before water reaches the ceiling. Finding water in it means the primary already overflowed upstream. We treat that as the warning it is, find why the primary backed up, and confirm the float switch will catch it going forward.

How we diagnose it

• Confirm which unit is overflowing, since attic installs here are often additions or outbuildings separate from the main slab-built house.
• Pour water through the primary pan and watch where it goes: a clean drain, a clog, or a pan that won't hold water.
• Lifting the float switch, we verify the system shuts down as it should.
• Both the primary and secondary pans get checked for cracks, rust-through, and standing water.
• Check the drain line's slope along its full run, and confirm a condensate pump, if present, clears its tank under power.

$99 diagnostic, credited toward the repair. You get a written quote before any work begins.

Condensate Leak in the Attic in Portola Valley: common questions

Nearby and related

Condensate Leak in the Attic near Portola Valley: Woodside · Menlo Park · Los Altos Hills .

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