Symptom
Water leaking from the air conditioner
Water where water should not be. If there is a stain on a ceiling below an attic air handler, switch the system off now and read the first paragraph.
If there is water on a ceiling, do this now
Turn the system off at the thermostat and leave it off. Do not switch it back on to see if it has stopped. While the system runs, the coil keeps producing condensate, and if the drainage has failed that water keeps arriving in the ceiling.
A stain on a ceiling beneath an attic air handler means the primary drain has failed and the secondary pan is overflowing or has rusted through. That is the point at which an inexpensive drain clearing becomes a drywall repair.
Then call. This is one of the genuinely time-sensitive HVAC problems, because the cost climbs by the hour.
What to look at
- The drain pan under the indoor coil. Standing water means the line is not carrying it away
- The secondary pan beneath the air handler. Any water there means primary drainage has already failed
- The outdoor end of the drain line. It should drip steadily while the system runs
- The secondary drain outlet, often above a window or under an eave. Water there is a warning sign
- Ceiling below the air handler, for staining or sagging
Water dripping from a pipe high on an exterior wall is the secondary drain telling you the primary has blocked.
Call (866) 427-9264Causes
Where the water is coming from
A blocked condensate drain line
The overwhelmingly common cause. The drain line is a permanently damp pipe in a warm attic, which is an excellent environment for biological growth. Over a season that growth restricts the line and then blocks it. Water backs up into the pan, fills it, and overflows.
This is straightforward to clear and straightforward to prevent, which is why drain service is the highest-value item in a maintenance visit in this climate. See clogged AC drain lines.
A frozen coil that has thawed
A coil frozen into a block of ice releases all of that water at once when it thaws, at a rate the drain pan was never designed to handle. The result is overflow even with a perfectly clear drain line. If you have had ice on the system recently, this is very likely your answer. See frozen AC coil.
A cracked or rusted drain pan
Primary pans are plastic or metal and both fail eventually. Metal pans corrode from years of standing water, and plastic pans crack. Once the pan itself leaks, the drain line can be perfectly clear and water will still find the ceiling.
A disconnected or badly sloped drain line
Drain lines work by gravity. A line that has come apart at a joint, sagged between supports, or was installed with insufficient fall will hold water and eventually back up. Sagging is common where flexible line has been run over a long attic span without adequate support.
A failed condensate pump
Where gravity drainage is not possible, a small pump moves condensate to a drain. Pumps fail, floats stick, and discharge lines block. When the pump stops, the reservoir overflows.
Poor insulation on the refrigerant lines
A less common cause worth knowing about, because it looks like a leak and is not. Cold suction line running through a humid attic with damaged or missing insulation will condense water along its length, which drips. The system is fine. The insulation is not.
Why this matters more here
Attic air handlers and finished ceilings
Most two-storey houses in Sugar Land, Missouri City and Stafford have the air handler in the attic. That is a sensible use of space and it has one significant consequence: the equipment producing several gallons of water a day sits directly above finished ceilings.
The system is designed for that. There is a primary drain, a secondary drain, an emergency pan and usually a float switch, and each is a layer of protection. The problem is that the layers fail silently and in order. The primary line blocks, and unless the float switch catches it you never know. The secondary drain starts running, and unless you notice water dripping from a pipe under the eave you never know that either. By the time anything is visible indoors, all the earlier warnings have already been missed.
Which is why the pipe that occasionally drips above a window matters. That is the system telling you something well before the ceiling does.
Worth knowing before you call
- Where you can see water: pan, ceiling, wall or outside
- Whether the ceiling is stained, damp or actively dripping
- Whether the indoor unit is in the attic, a closet or a garage
- Whether the system recently had ice on it
- Whether the system has shut itself off
24/7 emergency HVAC service. Office monday - saturday, 9:00am - 6:00pm.
Leave this part to a technician
Do not bypass a float switch to get cooling back. It has shut the system down because water is where it should not be, and defeating it removes the last thing standing between a blocked drain and your ceiling.
Do not pour bleach into a drain line as a routine measure. It corrodes metal drain pans and fittings over time. Technicians use treatments formulated for the job.
If a ceiling is sagging or bulging with trapped water, keep people out from underneath it. That is a structural risk rather than an HVAC one.
Related pages
Clogged AC drain line
The cause behind most of these leaks, and how it is cleared.
Float switch keeps tripping
The safety device that prevents this, and why it trips.
Frozen AC coil
A thawing coil overwhelms a drain pan that is working perfectly.
HVAC maintenance
Annual drain service, the cheapest insurance available here.
Emergency AC repair
Water through a ceiling is a genuine emergency.
AC repair
What a diagnostic visit covers.
Water leak questions
Should I turn the AC off if it is leaking?
How much water does an AC actually produce?
Is a little water in the drain pan normal?
My AC leaks only sometimes. Why?
Water above a finished ceiling is one of the few HVAC problems where waiting genuinely costs more.
Call (866) 427-9264Water where it should not be
Turn the system off, then call. 24/7 emergency HVAC service, because this one gets more expensive the longer it runs.