Mechanical, Electrical, and Plumbing Coordination
What is tested
MEP coordination tests how the trades fit together: sleeves, clearances, slopes, access, testing, and commissioning. Questions often involve code clearances and interference.
Core rules
- Coordinate before installation: combine plumbing, HVAC, electrical, and fire protection in a clash-detection model; resolve ceiling and structural conflicts.
- Plumbing: drain lines slope toward the drain; a common rule is ¼ in per ft for 2 in and smaller and ⅛ in per ft for larger. Vents protect traps.
- Electrical: working space in front of panels is typically 30 in wide, 36 in deep, and 6½ ft high; do not block panels.
- HVAC: ducts need clearance and access; fire dampers are required at rated assemblies; condensate drains must slope.
- Access panels are required for concealed valves, dampers, and equipment. Test and balance, pressure tests, and commissioning verify performance.
Worked example
A 20 ft drain run at ¼ in per ft falls 20 × 0.25 = 5 in. If the upstream invert is 100.00 ft, the downstream invert is 99.583 ft because 5 in = 0.417 ft. Reasoning: convert inches to feet before subtracting; slope is drop per horizontal foot, not per pipe length along the slope.
Traps
Running drains flat; burying valves without access; sizing electrical working space from the panel door only; ignoring firestopping at rated walls; coordinating after rough-in.