AC New Install — Condensate Drain Slope and Trap

Step 1 — Slope ≥1% + diameter ≥20 mm + P-trap installation

Check: Minimum slope: 1% (10 mm drop per 1 m, IMC/KS) — practical 2% (1/4 inch per foot). Minimum diameter: 20 mm (3/4 inch). Trap depth: 50 mm per ≤0.05 in.WC of static pressure. Without trap = indoor static pressure pulls condensate back → indoor leak or coil flooding.

What to do: Pipe = HDPE or PVC ≥20 mm diameter. Slope = ensure ≥1% with level (10 mm drop per 1 m). Install P-trap ≥50 mm depth. After install, pour 2 L water → verify drain within 90 sec. Below 5°C ambient zones = add heat trace or insulated pipe.