Carlo DeLuca, Master plumber As an Amazon Associate I earn from qualifying purchases. Some links are affiliate links.
The closet door was open. Morning light came in from the hall. The air handler sat on its stand over a metal pan. The pan held standing water. A short white PVC nipple stuck out from the side of the pan. Nothing was attached to it. Water dripped from the open end onto the concrete floor and ran toward the baseboard.
An overflow pan is the last stop before water leaves the closet and finds the ceiling below. The primary condensate line is supposed to carry the water away first. When that line clogs or loses its fall, the coil makes water into the pan. The pan is supposed to have its own drain. That drain is usually a nipple or a fitting on the side of the pan with a hose or a short PVC run that dumps outside or into a pump. When the nipple has no hose, the pan fills and then overflows through the open fitting. The water never leaves the room. It just moves from the pan to the floor.
This is not a float switch that sits too high. The switch can still cut the unit if the water rises far enough. This is the path out of the pan. Someone installed the pan and left the drain fitting open. Or the hose fell off and nobody put it back. The outdoor dump can look clear. The primary line can be open. The water still ends up on the floor because the pan drain was never finished.
After-work check
Open the air-handler closet after the unit has run through the afternoon. Look at the pan first. Standing water means the coil made condensate and the primary path did not take it. Then look at the side of the pan. A PVC nipple or fitting with no hose or tube attached means the secondary drain was never hooked up. Water will leave the pan through that open end once the level reaches it. Follow any hose that is present. It should leave the closet and dump where you can see it. The closet guide shows the rest of the assembly: air-handler closet. After a heavy band the same overflow can stain the ceiling: after-storm.
Do not
Do not keep running the air to dry the closet. You are making more water into a pan that dumps on the floor. Do not pour cleaner down the primary line and call the pan fixed. The primary can be clear. The pan drain is the missing piece. Do not treat a wet floor under the closet as a humidity problem first. The house can feel fine while the closet holds water the pan never sent outside. Measure living-space relative humidity (RH) with Reed if the house still feels heavy after the pan is dry and the hose is on: how to measure. Do not open a pressurized supply line. The water in the pan is condensate. Do not ignore the open nipple because the floor looks only a little wet. The next run will make more.
Run this
- Shut the unit at the thermostat and at the breaker if the floor is wet. Empty the pan into a bucket. Confirm the water stops when the coil is off.
- Check the pan drain. The nipple or fitting on the side of the pan needs a hose or a short PVC run that leaves the closet and dumps outside or into a working pump. Attach the hose. Secure it so it cannot fall off. Confirm the outdoor dump is clear.
- Confirm the primary line has fall and the trap holds water. Leave a leak puck in the dry pan so the phone knows next time the pan fills. The overflow pan should text you before the ceiling does. See the overflow pan should text you.
A hose on the pan drain keeps the water from leaving the closet through the open fitting. When the primary path is blocked the pan still has a way out. The PumpSpy CP-120 is assembled in the USA and built to move the volume a Florida closet makes when both drains are doing their job.
FloridaDamp is an Amazon associate — we earn from qualifying purchases. I still point at this one because it is an assembled-USA condensate pump that will actually drain a closet pan, not because anyone paid for a review.
Hook up the hose. Empty the pan. Keep the drain where the water can leave.
If it’s useful, it’s beautiful.
Carlo DeLuca is a third-generation master plumber writing from coastal Florida. Notes are educational. Not a service call.