How to bid plumbing work as a subcontractor

Start with what you are actually bidding

Settle the boundaries before you measure a single foot. The plumbing package on a commercial job is split across several MasterFormat divisions, and the money leaks at the splits rather than in the pipe.

• Division 22 Plumbing is your core: 22 11 00 Facility Water Distribution, 22 13 00 Facility Sanitary Sewerage, 22 14 00 Facility Storm Drainage, 22 30 00 Plumbing Equipment, 22 40 00 Plumbing Fixtures.
• Division 33 Utilities is the site work: 33 11 00 water utility distribution, 33 31 00 sanitary utility sewerage, 33 41 00 storm utility drainage. On most jobs that is a different sub entirely.
• Facility Natural-Gas Piping is 23 11 23, in the mechanical division, even though the gas is usually drawn on the P sheets and usually installed by the plumber. Section number and installer are two different questions.
• 22 60 00 Gas and Vacuum Systems for Laboratory and Healthcare Facilities is medical and lab gas. Treat it as a separate scope with separate certifications, never as a line inside plumbing.

Then the five foot line. Most specifications end Division 22 five feet outside the building and hand everything beyond it to Division 33. Three things go wrong with that. The five feet is a specification convention, not a code rule, and the plumbing code defines the building drain to building sewer transition a short distance outside the wall measured in inches, so the code line and the spec line are not the same line. The civil drawings often stub the lateral at a different point with a stated invert. And the note that actually assigns the connection is frequently on a C sheet that the plumbing bidder never opens. State in your proposal exactly where your pipe stops, by station or by distance off the building line, and state the invert you assumed.

The second boundary is the fixtures. Supply and install, install only, or owner furnished contractor installed are three different numbers. On an owner furnished job you still own the carriers, the supports, the stops, the supplies, the traps, the setting labour and the warranty argument when a fixture arrives damaged. Say which one you priced.

Read the drawings for your sheets, not the whole set

• P sheets carry the scope, and there is more than one plumbing plan. The underground plumbing plan is a separate sheet from the above slab plan. The waste and vent isometrics, the domestic water riser, the gas riser, the fixture schedule and the equipment schedule are all separate again.
• Risers and isometrics beat plans. Plan view gives you routing and location, not vertical footage. Stacks, fixture drops and vents through the roof exist only on the isometrics, and on a fixture heavy floor the vent footage can rival the drainage footage. See DWV for how the two sides split.
• A sheets carry the enlarged restroom plans and interior elevations: mounting heights, whether the water closet is wall hung on a carrier, and whether the wall is furred deep enough to take one.
• C sheets carry the lateral, the invert at the point of connection, the water service size, the meter and vault location, and whether the backflow preventer assembly sits in an exterior vault or inside your building. They also carry the in ground grease interceptor, which drags a second underground run and an excavation question with it.
• S sheets decide your underslab routing. Grade beams, pile caps, footings and depressed slabs are things you cannot trench through, and the slab pour joints tell you how the work will be sequenced.
• M sheets are full of your connections. Every rooftop unit condensate drain, boiler make up water line and humidifier feed is a connection somebody has to price.
• The specification sets pipe material by service and size, which is a large cost delta. Cast iron against PVC on the drainage side, and copper against PEX on the supply side, are not close in either material or labour. It also sets insulation, testing, disinfection and who owns firestopping at your penetrations.

Getting the quantities right

Plumbing is bid in a mix of units, and the mix is the point. Fixtures and equipment are each. Pipe is linear feet by size, by material and by service, with underground and above slab kept as separate line items because the labour is nothing alike. Fittings, valves, cleanouts, floor drains, roof drains, hose bibbs, carriers and trap primers are each. Insulation is linear feet by size and thickness. Trench and backfill are cubic yards, if they are yours.

What the obvious fixture count misses:

1. Carriers and trim. A wall hung water closet needs a carrier, which is on the details rather than the fixture schedule, and it is real money each.
2. The second and third underground run. Grease waste, acid waste on a lab job, and condensate are separate systems that no fixture count will reveal.
3. Trap primers. Every floor drain that needs one needs a water line run to it, shown as a small note and priced as real pipe.
4. Testing and disinfection. Pressure testing, chlorination and bacteriological clearance on the domestic water system are line items, not overhead.
5. Roof drainage. The drain body is yours under 22 14 00, the flashing and membrane tie in belongs to roofing, and horizontal storm piping in conditioned space usually needs insulation against condensation. Beyond the building it becomes the site storm drain and someone else's package.

The gotcha that costs more than any of those: underslab rough-in labour is set by the concrete schedule, not by your productivity. The underground rough has to be laid, tested, inspected and backfilled before each pour. If the slab goes in six sections, you mobilise six times, and every mobilisation carries a crew, a layout, a test and an inspection whether it covers four hundred feet of pipe or forty. Count the pour sequence off the structural sheets, price the mobilisations as their own line items, and write the sequence you assumed into the proposal. A footage only takeoff prices a job you will not get to build.

On sizing, plan and spec work hands you the pipe sizes and the fixture unit math is the engineer's. Two exceptions make it yours. A performance specification or design build bid puts the sizing, and the engineering cost, on you. And an addendum that swaps fixtures can change DFU and WSFU totals enough to resize pipe, so re take off the affected runs rather than assuming the sizes held.

What the GC checks when leveling plumbing bids

Bid leveling is the GC normalising every plumbing proposal to one common scope. Expect them to check:

• Where your scope stops outside the building, and the invert you carried there.
• Fixture count and fixture responsibility, item by item against the schedule.
• Trench, bedding, backfill, compaction and compaction testing, plus spoils removal and who eats rock or groundwater.
• Gas piping, yours or the mechanical sub's, including rooftop supports, painting and labelling.
• Water service, meter, vault and backflow assembly, and which utility fees are the owner's.
• Medical and lab gas, including the third party verification a facility code job requires, which is not your own labour.
• Insulation, firestopping, sleeves, seismic bracing, testing and disinfection, each of which a silent bid will be assumed to include.
• Unit prices and allowances, so changes are priced without re bidding.

Anything you left silent gets filled in with an assumption, and the assumption will not favour you.

Structure the proposal so it survives leveling

1. The number, with the fixture count and the specification sections it covers.
2. Inclusions, as items rather than a paragraph.
3. Exclusions, the same way. This is the most valuable section in the document.
4. Clarifications and assumptions. Where your pipe stops and at what invert, the pour sequence and mobilisation count you priced, fixture supply responsibility, trench and compaction responsibility, rock and dewatering, temporary facilities.
5. Unit prices for the likely adds: per linear foot of underground pipe by size, per fixture, per cubic yard of rock excavation.

Where this fits

Price your markup on top of a cost you can defend line by line, and keep the takeoff that produced it. If you are running that takeoff, Ruh reads the drawing set, measures the scope, and prices the measured quantities against your own price book, with every line traceable back to the sheet it came from. That traceability is exactly what you need when a GC calls to ask why your underground number is different from everybody else's.