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CBO
When inspecting condensate drains, one of the most important steps is confirming whether the manufacturer requires a trap. The International Mechanical Code makes this clear in Section 307.2.4:
The commentary drives the point home. The appliance or equipment manufacturer determines if a trap is needed and often specifies its depth and configuration. These traps are not plumbing traps. They serve a different function entirely.
Condensate traps are installed to prevent air from being pushed or pulled through the drain piping. Without a trap to block airflow, condensate may not drain properly, leading to pan overflow or unusual water depth in the drain pan. This is especially true for pull-through cooling coils, which may not drain at all without a trap. In addition to functional issues, airflow through an untrapped drain wastes energy.
For ductless mini-split systems, Section 307.2.4.1 requires an inline check valve or a trap. The choice depends on the indoor unit design, but the purpose is the same: prevent airflow from interfering with condensate drainage and stop air from escaping through the drain line.
TBCF Takeaway: You cannot determine trap requirements by looking at the installation alone. The manufacturer’s installation instructions must be reviewed on every job. Without them, you have no way of knowing if the equipment is operating as designed.
The commentary drives the point home. The appliance or equipment manufacturer determines if a trap is needed and often specifies its depth and configuration. These traps are not plumbing traps. They serve a different function entirely.
Condensate traps are installed to prevent air from being pushed or pulled through the drain piping. Without a trap to block airflow, condensate may not drain properly, leading to pan overflow or unusual water depth in the drain pan. This is especially true for pull-through cooling coils, which may not drain at all without a trap. In addition to functional issues, airflow through an untrapped drain wastes energy.
For ductless mini-split systems, Section 307.2.4.1 requires an inline check valve or a trap. The choice depends on the indoor unit design, but the purpose is the same: prevent airflow from interfering with condensate drainage and stop air from escaping through the drain line.
TBCF Takeaway: You cannot determine trap requirements by looking at the installation alone. The manufacturer’s installation instructions must be reviewed on every job. Without them, you have no way of knowing if the equipment is operating as designed.