How to take off a piping ISO drawing

A piping takeoff lists the quantities on a set of ISOs: pipe, fittings, flanges, valves, gaskets, bolting, welds, and supports. This guide goes through one drawing in order, then rolls the set up into an MTO.

Cory LaChance

Cory LaChance

Founder, TakeOffTrak ·

What you need

  • The ISO set.
  • The line list, if the job has one.
  • The piping specs.
  • The scope documents. The ISOs show what gets built. The scope documents say which part is yours.

Each ISO has a drawing number, a sheet number, and a revision in the title block. One line can run across more than one sheet, and each sheet has its own BOM. The legend on the drawing defines the weld and support symbols used on it.

One drawing, step by step

  1. 1

    Read the title block

    Drawing number, sheet number, revision, line number, size, piping spec, and any paint, insulation, and test callouts.

  2. 2

    Take off the BOM

    Copy every row: item number, description, size, quantity, and unit. Pipe is in length. Fittings, flanges, and valves are by each. A reducing item has two sizes, like a 6 x 2 reducer.

  3. 3

    Split shop and field

    If the BOM prints shop and field sections, use them. If it does not, the scope documents set the split.

  4. 4

    Count the welds

    Count every weld by type and size: butt welds (BW), socket welds (SW), and olet welds. Then mark the field welds (FW), and the field fit welds (FFW) among them. See shop weld vs field weld.

  5. 5

    Count the supports

    Take supports off the BOM, or off the support marks on the drawing. Note the support tag with the count.

  6. 6

    Check your count against the drawing

    Every weld, fitting, and support on the ISO ties to a line in your takeoff.

Roll the set up into an MTO

One ISO gives you one BOM. The rollup groups every BOM row across the set by item, size, and spec. That rollup is the material takeoff, or MTO.

Weld counts roll up the same way: by type, size, and shop or field. A diameter inch (DI) is the weld count times the nominal pipe size. Twelve 6 inch butt welds are 72 diameter inches.

Where TakeOffTrak fits

TakeOffTrak does the counting. You upload the ISO set. It reads the title block and the BOM, finds the welds, picks the supports out of the BOM, and marks every item on the drawing. You check the drawing with the marks on, fix anything that is wrong, and export to Excel. Scope, spec, and pricing stay with you.

See weld takeoff, piping MTO, and support takeoff, or open the demo and try it on a sample ISO.

Common questions

Do I take off from the ISO or the line list?
Both. The ISO has the materials, welds, and supports. The line list has line data such as paint, insulation, and test requirements.
What is the difference between a BOM and an MTO?
The BOM is the material table printed on one ISO. The MTO is every BOM on the job rolled up by item, size, and spec.
What is a diameter inch?
The weld count times the nominal pipe size. Four 2 inch socket welds are 8 diameter inches.

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