Plumbing estimating, CSI Division 22, is the business of pricing the water, waste, gas, and venting systems that run through a building. You work from the plumbing plans, the riser diagrams, the fixture schedule, and the details. Every water closet, lavatory, floor drain, cleanout, foot of pipe, valve, and hanger has to be counted, measured, priced, and labored into a bid that holds water when the field work starts. Plumbing is a trade where the underground and the rough are two different jobs and both have to be in the same estimate.
What You Are Estimating
Division 22 covers the domestic water supply, the sanitary and storm drainage, the natural gas piping, the plumbing fixtures, and the supporting equipment. The major cost groups are fixtures, underground piping, above ground rough piping, vents, gas piping, and equipment. Fixtures include water closets, urinals, lavatories, sinks, service sinks, floor drains, and drinking fountains. Equipment includes water heaters, booster pumps, sump pumps, ejector pumps, water softeners, and backflow preventers.
On a typical commercial job the fixture list comes off the fixture schedule, the underground piping comes off the plumbing plan at the floor, the above ground piping comes off the riser diagrams and the floor plans, and the gas piping comes off the gas plan. You also carry the sleeves, the hangers, the fire stopping, the floor drains, the cleanouts, and the roof penetrations because every one of those is a line item on a plumbing estimate.
Units and Workflow
Plumbing quantities are counts and linear feet, with the pipe priced by the foot and labored by the foot or by the fitting. Fixtures are counted. Pipe is measured in linear feet by system, by pipe type, and by diameter, with the fitting labor either built into the foot price or counted separately. Hangers are counted by type and spacing. Valves are counted by type and size. Cleanouts, floor drains, and roof penetrations are counted.
The workflow runs underground first, rough second, finish third. You start with the underground because the sanitary and the storm drainage have to be in before the slab. You take the building sewer, the building drain, the storm drainage, and the under slab water. Then you run the rough above ground: the domestic hot and cold water risers, the sanitary and vent risers, the gas piping, and the branch lines to each fixture. Then you run the finish: setting the fixtures, the trim, the faucets, the stops, and the testing. Each phase has its own labor rate and its own risk.
Step by Step Estimate
First, set up the estimate with your labor rate and your labor units. Pipe labor comes from the PHCC manual or your own shop average by pipe type, by size, and by system. Cast iron soil pipe, PVC DWV, copper tube, and PEX each carry their own labor unit. The labor rate comes from your shop average plumber rate plus burden.
Second, do the fixture takeoff. Count every fixture from the schedule and tag it by type and by manufacturer. Price each fixture as an assembly that includes the fixture, the trim, the stops, the carrier where the wall hung unit needs one, and the testing. Third, do the underground takeoff. Measure the building sewer and the building drain in linear feet by pipe type and size, count the cleanouts, and count the floor drains. Fourth, do the rough takeoff. Measure the water risers, the sanitary risers, the vent risers, and the branch lines. Count the valves, the hangers, and the sleeves. Fifth, do the gas takeoff. Sixth, price the equipment. Seventh, load the spreads: labor burden, permits, inspection fees, excavation and backfill on the underground, and your overhead and profit.
Where the Money Goes
On a commercial plumbing package the fixtures and the rough piping together run 50 to 65 percent of the installed cost. Fixtures are bought in small quantities and the fixture price drives the section, with the carrier, the stops, and the trim adding real cost behind every wall hung water closet. Underground piping runs 10 to 20 percent, with excavation, backfill, and the under slab work carrying labor that is hard to see on the plan. Above ground rough piping runs 20 to 30 percent, and this is where the trade is won or lost because the fitting count and the hanger count hide in the riser diagrams.
Equipment runs 8 to 15 percent, with water heaters and booster pumps carrying the section on jobs that need them. Gas piping runs 5 to 10 percent. Labor overall runs 35 to 45 percent of the installed cost on commercial plumbing, which is one of the higher labor trades because every fitting is hand assembled and every joint is tested. A missed fitting is not just the cost of the fitting, it is the labor to install it and the labor to test it.
Common Mistakes
The first mistake is undercounting fittings. A tee, an elbow, or a cleanout is easy to miss on the riser diagram, and on a branch heavy job the fittings can equal the straight pipe in cost. The second mistake is forgetting the hangers. Pipe has to be supported, and the hanger type, the spacing, and the anchor all carry a cost and a labor unit. The third mistake is missing the sleeves and the fire stopping. Every pipe that crosses a rated wall or floor needs a sleeve and a fire stop assembly.
The fourth mistake is underpricing the underground. The building sewer is measured on the plan but the excavation, the bedding, the backfill, and the compaction are separate costs, and a high water table or rock can double the underground line item. The fifth mistake is pricing fixtures from a catalog without the carrier and the stops. A wall hung water closet needs a carrier, and forgetting the carrier cuts a real cost out of the bid. The sixth mistake is forgetting the test. Every system has to be tested, and the test labor and the test equipment are line items.
Putting It Together
A clean plumbing estimate is built underground first, rough second, finish third. You take the fixture schedule for the fixtures, the plumbing plan for the underground, the riser diagrams for the rough, and the gas plan for the gas. You count the fixtures, measure the pipe, count the fittings and the valves and the hangers, price the material, apply the labor, and load the spreads. When the bid number lands you compare it to the last similar job by the cost per fixture and the cost per square foot. If the number is out of line you go back to the riser diagrams and the fitting count before you submit. Plumbing is a trade where the fittings and the hangers hide the money, and the takeoff is where most plumbing subs make or lose the job.