How to bid plumbing jobs comes down to one repeatable sequence: read the plans and specifications, take off the quantities the drawings show, convert those quantities into labor hours using labor units, price the material, add overhead and markup, and write a proposal that states exactly what the number covers.
This page walks the sequence end to end, from the first sheet to the submitted bid.
Read the plans and specs
Bidding starts with the documents, not the calculator.
A plan-and-spec bid package puts the drawings, the specification book, and the bid instructions in front of you, and each answers a question the others don't: the drawings show what is designed, the specifications decide what is acceptable, and the instructions set the form your proposal has to take.
Read the specifications with as much care as the plans.
The spec book names the acceptable manufacturers and models fixture by fixture, the pipe materials system by system, and the installation standards the finished work must meet — and those choices move the price.
Two sets of drawings that look alike can price worlds apart because the specs call for different fixture lines or different jointing methods.
Read the bid instructions just as closely.
They fix the proposal form, the deadline, the base bid and any alternates the owner wants priced separately, and the cut-off for questions.
Whatever the drawings leave ambiguous goes into a request for information before that cut-off — an assumption you price silently is a dispute you inherit after award.
Work from the legend printed on the set you are pricing.
Our research found no citable standard symbol chart to check a drawing against, so the legend on the current set is what defines each symbol.
Do the takeoff
The takeoff turns drawings into quantities, and everything after it prices that list.
Fixtures and equipment are counted, straight off the fixture schedule; pipe is measured run by run, by size and material, through every offset the drawing shows.
Measuring through offsets is where takeoffs quietly go wrong.
A drawing shows an offset flat, but the pipe travels through it at an angle, and the angle's multiplier is fixed geometry — the pipe in the offset is the offset distance times 1.414 for 45-degree fittings, 2.000 for 30-degree, 1.155 for 60-degree, 2.613 for 22-1/2-degree, and 5.126 for 11-1/4-degree fittings.
Counting those offsets as straight runs is how a takeoff comes up short on pipe that was there all along.
Separate the systems
Split the takeoff into sanitary drainage, vent, domestic water, and gas before measuring, so each system totals on its own line.Count fixtures against the schedule
Fixture and equipment counts come off the fixture schedule, checked against the plans rather than replaced by them.Measure pipe by size and material
Follow each run through its offsets and apply the angle multipliers, so the length reflects the pipe the crew will actually install.Capture what carries and connects
Hangers, supports, valves, and specialty fittings are quantities too — MCAA's WebLEM carries labor hours for hangers as well as pipe and fixtures.
The code table behind the drawings doubles as a cross-check on your counts.
Under the 2024 International Plumbing Code (IPC), Table 709.1 assigns these fixtures drainage fixture unit (DFU) values:
| Fixture (IPC 2024 Table 709.1) | DFU | Minimum trap |
|---|---|---|
| Lavatory | 1 | 1-1/4 inch |
| Bathtub | 2 | 1-1/2 inch |
| Kitchen sink, domestic | 2 | 1-1/2 inch |
| Automatic clothes washer, residential | 2 | 2 inch |
| Water closet, private (1.6 gpf) | 3 | — |
| Bathroom group (with 1.6-gpf water closet) | 5 | — |
If the fixture units you count do not square with the pipe sizes on the drawings, that mismatch is a question for the designer before bid day, not an adjustment you make quietly inside the estimate.
The same counts feed the labor and material pricing that follows, which is why the takeoff gets checked before anything is priced.
Code values are jurisdiction-specific
Apply labor units
Labor turns quantities into hours through labor units.
A labor unit is expressed in man-hours to install one unit of material — such as a foot of pipe — one individual item — such as a fitting or a valve — or to perform one specific task, such as welding a joint.
Multiply the unit by the takeoff quantity, and the hours total across the job.
One published reference is MCAA's WebLEM — the Labor Estimating Manual from the Mechanical Contractors Association of America.
It is a reference of labor hours for installing piping systems, plumbing fixtures and equipment, HVAC and refrigeration equipment, hangers, and more, so the takeoff lines from the last step map onto published units.
MCAA describes two ways to estimate piping labor with it.
The Component Method carries labor per pipe, fitting, and valve — joint labor, handling, testing, and installation included.
The Work Activity Method prices separate work activities instead, which makes splitting shop hours from field hours easier.
Several estimating-software providers are licensed to include MCAA labor units in their packages, and MCAA, MSCA, and PCA members get access to WebLEM free.
Book units are a starting point, and the units that hold up are the ones adjusted to your crews.
A shop's own production history — what its people actually did on similar buildings, under its conditions — is the correction layer over any published manual.
Hours become dollars when you multiply them by the loaded crew rate: the wage plus the taxes, insurance, and benefits that ride on payroll.
The back-and-forth between quantities, units, and rates is the daily work of the plumbing estimator — our role guide covers the seat itself, its pay data, and how field plumbers move into it.
Material pricing
Material pricing starts from the takeoff totals, priced against current supplier and distributor numbers.
Prices move, and an estimate priced off a stale list carries the gap straight into the bid, so the pricing run should be as recent as the bid schedule allows.
Price what the specification names.
If the specs call out a specific fixture model or a pipe material, the bid is for that item — a substitution is a change to propose to the owner and the designer, not one to make quietly inside the estimate.
Then sweep the takeoff for what surrounds the pipe: hangers and supports, valves, specialty fittings, and the consumables installation burns through.
Lead times belong in this step too — a long-lead item discovered after award squeezes the schedule, so it is cheaper to meet during pricing.
Waste and breakage get an allowance as well, and the honest number there comes from your own record of what never made it into the system, not from a figure copied from elsewhere.
Overhead, markup, contingency
Direct cost is what the job consumes: material, labor, equipment, and any subcontracts the scope includes.
Overhead is what the business spends whether or not this job exists — the office, insurance, vehicles, and the people who are not on the tools.
What that stack costs when you are starting a plumbing business is its own money decision, and it has to be recovered across the jobs, not absorbed by one of them.
Profit is the third layer, and it is where markup and margin get confused.
Both express the same profit, but markup measures it against cost and margin measures it against price — so the same profit shows a smaller margin than markup.
A shop that targets a margin but applies it as a markup prices a different job than it thinks it does.
Whichever convention you use, know which one you are using.
Contingency is the priced answer to what the drawings do not show: concealed conditions, existing systems that differ from the record drawings, and the surprises behind walls on renovation work.
You can carry it as an explicit allowance in the bid or hold it inside the number — either is defensible.
What is not defensible is never deciding: a contingency you never set consciously is margin you spent without noticing.
Write the proposal
The proposal is the estimate made contract-ready, and it is where estimating discipline becomes a sales asset.
It states the scope in plain language, the price and its basis, and — line by line — the inclusions and exclusions that tell the reader exactly what the number covers:
- The scope, tied to the drawings and specifications you priced
- The price, and its basis — lump sum, unit prices, time-and-materials, or whatever the bid form specifies
- The inclusions: the work and material the price covers
- The exclusions, stated as plainly as the inclusions
- Alternates priced separately, where the bid documents ask for them
- How long the price holds, and any qualifications attached to it
- Bonding and insurance evidence, where the bid documents require them
Exclusions do the quiet work in a plumbing bid.
When several shops bid the same scope, the one whose exclusions are explicit is the one whose number can be compared fairly — and the one that does not win a job it quietly mispriced.
A proposal that reads clean at opening also sets up the after-award life of the estimate: the number you won is the baseline the job is run against, and change orders trace back to exactly what your proposal said it covered.
Business information, not legal advice — have the contract language behind a bid reviewed by a qualified construction attorney before you sign it.