Plumbing Calculator | CrewMeasure

No fixtures entered yet. Nothing is sized until at least one fixture has a run length — the DFU total and the pipe-size check are both statements about the fixtures you list here.

Fitting allowance%Extra length added to cover fittings and bends. 10% is a typical starting point.

Pipe contextWhether this run is the main building drain, or a branch feeding into it — code allows different DFU loads for each.Selected pipe diameterinDFU (Drainage Fixture Unit) is a code unit for how much drainage load a fixture adds. This is the pipe size you plan to install, checked against the required minimum.

Flow rate (Poiseuille's Law)

Optional. Estimates laminar flow rate for a water-filled pipe from radius, length, and pressure differential. Fluid is fixed at water's viscosity near room temperature rather than an editable input. Skipped when left off.

Turn this on to estimate how fast water moves through a specific pipe run, given its radius, length, and pressure difference.

Hydrostatic pressure

Optional. Pressure by depth using water's standard density (P = 0.433 psi per foot of depth). Skipped when left off.

Turn this on to estimate the water pressure at a given depth, e.g. for a cistern or a deep fixture.

Catchment / reservoir volume

Optional. Converts a footprint area and depth to gallons -- e.g. sizing a rainwater catchment cistern or a shallow reservoir/basin. Skipped when left off.

Turn this on to convert a footprint area and depth into gallons, e.g. for sizing a rainwater cistern.

Drip waste estimator

Optional. Accumulates a drip rate into gallons wasted per day/month using the standard drops-per-gallon reference constant. Skipped when left off.

Turn this on to see how much water a slow drip wastes over time.

This run requires — ft of pipe sized for — DFU.

You'll need

Plumbing results

Warnings

INFO General reference only. Verify local requirements and adopted code before installation.
INFO Drain capacity here is read at 1/4 in per foot of fall, the only slope column the verified dataset carries. The code's capacity table publishes a separate column per slope, so a run laid at a different fall is sized from a column this tool does not have -- take that one from the code book rather than from the minimum diameter below.

Detail values

Base pipe footage: — ft
Total DFU: —
Minimum pipe diameter: 1.5 in at 1/4 in per ft fall
Selected pipe check: — at 1/4 in per ft fall

Assumptions

Fitting allowance: 10% -- estimated for an average run of fittings and bends, not a code or manufacturer figure
IPC data: IPC 2021 Tables 709.1 and 710.1
Drain capacity basis: Rows read at 1/4 in per foot of fall

Included: pipe footage with fitting allowance, DFU-based diameter check, P-traps for the fixtures that take one, closet flanges.

Not included: labor, permits, inspection fees, fixtures and fittings beyond what's itemized above.

Formula details

Pipe footage: sum(run length x fixture count) x (1 + fitting allowance %)
Total DFU: sum(fixture DFU x count)

Material List

About this calculator

Enter fixture runs and review sourced IPC reference sizing for supported common residential fixtures.

FAQ

Are local amendments included?

No. Verify the locally adopted code, since jurisdictions frequently amend IPC base tables.

Why are only some fixtures supported for DFU sizing?

Only fixtures with verified IPC Table 709.1 reference values are included. Unsupported fixtures are not guessed.

What is the minimum 3 inch rule for a water closet?

When a water closet is served, the calculator enforces a minimum 3 inch drain diameter regardless of the calculated DFU-based minimum.

Disclaimer

General reference only. Verify local requirements before installation.

Fixtures and pipe runs

DFU sizing