Dose a positive pressure drain need a trap? - Answers

A trap on a positive drain is used to avoid the 'contaminated' air in a HVAC system from traveling through the condensate line and entering into areas where it is unwanted. The trap becomes necessary when one condensate line is used for multiple units, especially if it is tied to other negative pressure drain traps. The negative pressure drain traps may not drain properly if they have to overcome the positive non- trapped pressure of another unit. It allows the condensate to drain more evenly, as well. Without a trap, the positive pressure from the unit can blow air through the drain with the water and cause 'spitting.' A trap on a positive pressure system may not always be necessary, but it is good practice to trap every drain and trap it properly. There are guidelines for both positive and negative pressure traps. Always follow the manufacturers recommendations.