TinnerFlow™3rd YearEquipment ConnectionsYELLOW · Check First
A draw-through unit can hold water in the pan if the trap does not overcome negative pressure. Verify unit type/static and rebuild the drain trap per manufacturer detail before water damages the cabinet.
On some AHUs, the fan can pull against the condensate drain. If the trap is too shallow or piped wrong, air gets pulled through the drain and water cannot leave the pan properly.
This is not just plumbing-looking PVC. Check the AHU manufacturer trap detail, negative/static pressure condition, drain pan elevation, venting, slope, and whether it is draw-through or blow-through. Repipe only to the approved trap profile.
Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.