Carlo DeLuca, Master plumber As an Amazon Associate I earn from qualifying purchases. Some links are affiliate links.
The hallway felt fine. The closet door was closed. When I opened it after work the metal pan under the air handler held a shallow lake. The outdoor dump was dry. The white PVC looked clear. The float switch on the side of the pan sat high, dry, and quiet. The coil was still making water.
A float switch is the last chance the closet has before the ceiling gets the message. It is supposed to rise with the water and open the circuit that feeds the outdoor unit. When the water hits the switch the compressor stops. The pan stops filling. You get a text or a quiet house instead of a stain. If the switch is mounted too high, or the float is stuck, or the arm never drops into the water, the coil keeps running. Florida air handlers make a lot of condensate in October. A switch that never sees the water is the same as no switch at all.
This is not a clogged trap. A clogged trap or a line with no fall fills the pan the same way, but the outdoor dump stays dry for a different reason. This is the switch itself. Someone set the bracket for a deep pan. The float needs more water than the pan can hold before it tips. The unit never sees the open circuit. The water keeps coming.
After-work check
Open the closet after the unit has run. Look at the pan first. A film or a standing puddle means water left the coil and did not leave the closet. Then look at the float. A dry float above the water line is the whole story. The outdoor dump being dry only proves the primary line never got the water. Follow the PVC from the coil to the wall. Confirm it still falls away. The closet guide shows the rest of the assembly: air-handler closet. After a heavy band the same backup can stain the ceiling below: after-storm.
Do not
Do not keep running the air to “dry the closet.” You are making more water into a pan the switch is ignoring. Do not pour bleach down the trap and call the switch fixed. The trap can be fine. The float is the problem. Do not treat a full pan as a humidity problem first. The hallway can feel fine while the closet holds water the coil never stopped making. Measure living-space relative humidity (RH) with Reed if the house still feels heavy after the pan is dry and the switch is set: how to measure. Do not open a pressurized supply line. The water in the pan is condensate. Do not cut the PVC because the pan is wet. The line can be clear. The switch never told the unit to stop.
Run this
- Shut the unit at the thermostat and at the breaker if the closet is wet. Empty the pan into a bucket. Confirm the water stops when the coil is off.
- Check the float height. The arm or the float body should sit low enough that a half-inch of water in the pan lifts it. If the bracket is high, lower it or have a licensed tech reset the switch so it opens before the pan overflows. A stuck float needs a free arm, not a new line.
- Confirm the outdoor dump is clear and the secondary stub is open. Leave a leak puck in the dry pan so the phone knows next time. The overflow pan should text you before the ceiling does. See the overflow pan should text you.
A switch that sees the water keeps the coil from filling the pan once the primary path is blocked. When the closet sits below the outdoor dump a pump still has to lift the water. The PumpSpy CP-120 is assembled in the USA and built to move the volume a Florida closet makes when the float is doing its 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.
Lower the float. Empty the pan. Keep the switch where the water can reach it.
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.