MEP
Drain-Waste-Vent (DWV)
The plumbing subsystem that removes wastewater from fixtures and vents sewer gases safely to the atmosphere above the roofline.
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In the Field
Every fixture trap requires a vent to prevent siphoning. Wet venting, air admittance valves (AAV), and studor vents are alternatives where running a vent to the roof isn't practical — verify local code acceptance. Slope drain lines 1/4 inch per foot for 4-inch and smaller pipe.
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Rule of Thumb
Drain slope is 1/4 inch per foot for 3-inch and smaller pipe. Avoid slopes steeper than 1/2 inch per foot — fast-moving water outruns the solids and causes chronic clogging.