In Plain English
Quick Answer
A drain pipe that carries dirty water from sinks and floor drains — but not toilet waste — to the main building drain.
Definition
Definition
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.
Context
Why It Matters in Bidding
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.
Example
Example
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.
See Also
Related Terms
FAQ
Questions Contractors Ask
How is waste pipe priced differently from soil pipe in a bid?
Waste piping typically runs at smaller diameters than soil stacks, so it carries lower material cost per foot but can require more fittings per fixture group. Estimators price each diameter and material separately, account for slope and hangers, and split the two in the takeoff to avoid double-counting fixture connections.
What scope details should I confirm before bidding waste piping?
Confirm pipe material specified, required slope, venting layout, and whether the sub or the GC sets and connects floor drains. Check the spec section for cleanout locations and fixture connection responsibility, since unclear vent and cleanout scope is a frequent source of post-award change orders on plumbing work.
Does waste pipe slope affect labor cost on an estimate?
Yes. Maintaining 1/4 inch per foot grade across long horizontal runs takes added layout and hanger labor, and tight ceiling or slab depths can force fittings or offsets that slow installation. Estimators add labor hours where structure or coordination makes maintaining proper grade difficult.
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