Craft Quantities
Plan & Takeoffs

By trade

Plumbing calculators

Plumbing sizing is a chain of consequences: what has to flow decides the pipe, the pipe decides the friction, the friction decides the pressure, and the pressure decides whether the top-floor shower works. Drainage is the same chain run by gravity, where a fall too steep fails as surely as one too shallow.

  • 37Calculators
  • 3Parts of the site

How plumbing is measured

Diameters chosen from a flow rate or a loading unit total, linear metres for runs, and counts for fittings — each of which adds an equivalent length of pipe to the friction calculation. Vessels and tanks are sized by volume against a demand profile.

Where plumbing sits on this site37 across 3
37

Plumbing & HVAC18

Materials & Quantities18

Sustainability & Compliance1

What gets left off a plumbing order

  • Fittings as equivalent length. A run with many elbows behaves like a much longer straight pipe, and that is what undersizes a system.
  • The fall on a drain: too shallow and it blocks, too steep and the solids are left behind by the water.
  • Expansion and the room for it — loops, offsets and clips at the spacing that lets a hot pipe move.
  • Insulation and heat trace on anything at risk of freezing or of losing its heat on the way.

Job takeoffs3

Where plumbers meet the rest of the job: each runs one of these calculators, with every other trade in the same job beside it.

Worked examples1

A real job estimated step by step, with this trade's steps counted.

Comparisons13

Two ways of doing the same work, weighed against each other.

Planners1

Work this trade out from a space rather than from a job.