A drain pipe that carries dirty water from sinks and floor drains — but not toilet waste — to the main building drain.
A drain pipe that carries liquid waste (without solid fecal matter) from sinks, floor drains, laundry equipment, and other non-toilet fixtures to the building drain. Waste pipes differ from soil pipes in that they do not convey toilet waste. They must be vented and sloped at the proper grade (typically 1/4 inch per foot) for self-cleaning flow.
On a plumbing takeoff, estimators must separate waste piping from soil piping because the two carry different loads, often use different diameters and materials, and price differently per linear foot. Misclassifying or undercounting waste runs leads to scope gaps the plumbing sub will catch as a change order after award.
Reviewing the mechanical drawings, a plumbing estimator counts 180 linear feet of 2-inch waste pipe serving the kitchen sinks and floor drains, then prices the labor to slope each run at 1/4 inch per foot before rolling it into the bid.
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