Condensate Done Right: Traps, Pitch, Floats, and the Callback You Never Get

Condensate is the least glamorous system on the job and the source of some of the most expensive callbacks — because when it fails, it fails as water damage.

Trap the primary drain where the equipment requires it. Coils under negative pressure will hold water in an untrapped line or pull air through it, and either way the pan overflows eventually. Match the trap depth to the unit's static pressure — the installation manual gives the number.

Pitch matters more than pipe size: a quarter inch per foot, consistently, to daylight or an approved drain. A run that sags holds water, grows the biofilm that plugs it, and turns into a service call every spring.

Put a float switch on everything. Primary pan, secondary pan, or inline on the drain — wherever the configuration wants it. Killing the system before an overflow is the cheapest insurance in the catalog, and inspectors increasingly expect it.

Where gravity can't get there — basement air handlers below grade, common in older mountain housing stock — a condensate pump is the answer. Check the lift rating against the actual rise, route the discharge somewhere legal, and wire the pump's safety contacts so a failed pump stops the system instead of flooding the mechanical room.