M.E.P.flow — Revit add-in Beta V1.021 · 27 Oct 2026

Click the route. M.E.P.flow sizes it, checks it and builds it.

Ducts, water pipes, drains and conduit for Revit 2024–2027. Give it the airflow, the fixtures or the cables, click the points, and it picks the size, applies the limit the code sets, steers round the beams and builds the run with every elbow. The plan below is the real rule set. Click on it.

A CADflow product

Draw Duct Office · 600 L/s
Level 1 · plan Click to start the run
CheckClick a start point on the plan.
Trade
Building
Written to the elements
See it built

One bay, four trades, fitted in the order a site fits them.

Drainage first, then the pump and the cold water, the air handler and its ductwork, then power. The numbers in the corner come from M.E.P.flow's own calculators, and the geometry is checked so nothing passes through anything, not even while it is being lowered in. Hover a trade to follow it.

One ribbon, three trades

Every button asks an engineer's question and draws the answer.

The M.E.P.flow tab has an HVAC, a Plumbing and an Electrical panel. Each button is one job: you give it what you know, it gives you the number, the check and, where there is something to draw, the elements.

HVAC

Air that is sized, not guessed.

  • Draw DuctAirflow, building type and a height limit. Equal friction at 0.8 Pa/m, velocity capped by the building, round or rectangular, elbows placed.
  • Fresh AirClick the room. Outdoor air by ASHRAE 62.1: people rate plus area rate for 40 occupancy types, with the air changes it gives.
  • Cooling LoadWalls, roof, glass and sun, people, lights, equipment and outdoor air. W, BTU/h and tons, the supply air that carries it and the breakdown.
Office main 10 m/s · branch 8 · residential main 5 · kitchen exhaust 12.7 min 2.5 · aspect ratio ≤ 4
Plumbing

Water that arrives, waste that leaves.

  • Draw PipeFixture units served and the material. Flow from the Hunter curve, size from the velocity limit, friction by Hazen-Williams or Darcy, hot and cold.
  • 2 %Draw DrainFixture units and a fall. Size from the DFU table, fall applied to the run, the code minimum enforced and the level at the end reported.
  • Water PressureSupply pressure less height, meter and friction, against what the top fixture needs. Tells you the margin or the pump head.
Velocity cold 2.4 m/s · hot 1.5 · fall ≤ DN65 2 % · DN75–150 1 % · IPC / UPC fixture units
Electrical

Conduit that pulls, circuits that hold.

  • Draw ConduitCable size and count, NEC or IEC. Fill at 40 %, the 360° bend limit between pull points, a pull box placed where one is needed, PVC expansion.
  • Circuit SizerLoad, voltage system and length. Breaker, cable, earth and voltage drop with ambient and grouping corrections, conduit to match.
  • Single LineThe panels and circuits already in the model drawn as a single-line diagram in a drafting view: each panel, what it feeds, ratings and loads.
Fill 40 % (3+ conductors) · bends ≤ 360° · voltage drop branch 3 % · feeder + branch 5 % · NEC Ch. 9 / IEC 60364
While you draw

Four things happen between your first click and your last.

A duct, a water pipe, a drain and a conduit drawn on the plan, sized and checked with every click, then turned to the 3D model they already are.

  1. start here main, Ø400
    Tees and branches

    Start on a run, get a tee.

    Begin a duct or pipe on an existing one and the branch is cut in with a tee (a duct falls back to a tap). End a drain on a sewer and it joins at the right height.

  2. beam A* on the obstacle grid
    Clash-avoiding routes

    Round the beam, not through it.

    Tick one box and each stretch is routed past framing and columns, host and linked, and past the ducts, pipes, trays and equipment already there, inside the storey.

  3. pull box · 360° 90° · 90° · 90° · 90° → box
    Pull boxes

    The fifth bend gets a box.

    Conduit may turn 360° between pull points. When a run passes that, a junction or pull box family from the project is placed instead of the elbow, so the cable can be pulled.

  4. MEP Design Flow (L/s)600 MEP Velocity (m/s)6.1 MEP Fill (%)34 MEP CheckOK
    Results on the elements

    The number stays with the duct.

    Flow, velocity, fixture units, fall, cables, fill and the check are written to every run as shared parameters; rooms carry fresh air, people and cooling load. Schedules read them.

Drainage, start to finish

From the WC to the septic tank, laid the way the code wants it.

Draw the sewer on the site plan and M.E.P.flow lays it at a true 2 % fall, turns it through 45° fittings, puts the cleanout at the building and sets the tank inlet above its outlet. Turn to the section to watch a flush reach the tank, then count every pipe, bend and wye into a schedule.

Gas, cooktop to tank

An LPG line from the kitchen island to the tank, sized and checked as you draw.

Draw Gas sizes the copper from the appliance load by Pole's formula, keeps the shut-off valve within 1.8 m, sleeves the pipe through the slab, sets the valve and regulators at the wall and the tank, buries it under a warning tape and checks the tank's distance from the house. Then it counts every metre, elbow, clamp and valve.

Water, home-run PEX

Shower, WC and vanity on a manifold, bent the way PEX is bent.

Home-Run takes each fixture's hot and cold PEX to a manifold, sizes every piece, upsizes a shared line where a tee adds a fixture, puts a hammer arrestor before every point, bends every turn at its minimum radius and checks how long hot water takes to arrive. Then it counts the coils, bend supports, stops, arrestors and nail plates.

Calculators

Two of the calculators, live.

Fresh Air and Circuit Sizer run here exactly as they do on the ribbon, minus the click on the room. Cooling Load and Water Pressure are in the add-in.

Fresh Air

ASHRAE 62.1 breathing-zone outdoor air: people rate × people + area rate × floor area.

Occupancy
Outdoor air—
People—
Area—
Air changes—
Check

Circuit Sizer

NEC, copper THHN at 75 °C terminations, continuous load at 125 %, voltage drop held to 3 %.

System
Breaker—
Current—
Cable · earth—
Voltage drop—
Conduit—
Check

The Check panel

The model is checked the way a reviewer checks it. Only faster.

Audit Model

Every run, one list.

  • Each duct over its velocity limit.
  • Each drain under its minimum fall.
  • Each conduit run over 360° between boxes.
  • Click a row, the element is selected.
Schedules

From the stored results.

  • Room load schedule: fresh air, people, cooling load.
  • Duct, pipe and conduit schedules with flow, velocity, fill and the check.
  • Built from shared parameters with fixed GUIDs, so they survive a reload.
MEP Design FlowMEP VelocityMEP Fixture UnitsMEP FallMEP FillMEP Check
Quantities

Every pipe, fitting and hanger, counted.

  • Length by size, with stock lengths and 5 % waste.
  • Fittings by type and angle: 45° bends, wyes, sanitary tees, elbows, caps.
  • Hangers, clips and saddles at code spacing: IPC 308.5, NEC 352.30, SMACNA.
  • Cleanouts, pull boxes, diffusers and valves. A Revit schedule, or a table in AutoCAD.
Product Library

Catalogue and office families.

  • Manufacturer catalogues as one CSV per range, dropped in a folder.
  • Your family folder scanned into the same list.
  • Filter by minimum rating, then load and place.
  • Only generic nominal sizes ship with the add-in; real data comes from the manufacturer.
Report Bug · Send Idea

A line to the people who built it.

  • One line, details, an email if you want a receipt.
  • You see the whole report before it goes; nothing from your project is in it.
  • No connection? It waits and goes with the next one.
ASHRAE 62.1 ventilationASHRAE Fundamentals duct friction and fittingsIPC · UPC fixture units, drainage fallHunter curve design flowNEC Chapter 9, 352, 358, 314IEC 60364 voltage drop, conduitRevit 2024 · 2025 · 2026 · 2027
BetaBeta V1.021 · 27 Oct 2026

Stop guessing sizes. Start clicking routes.

M.E.P.flow is in open beta and free while it is. One installer, Revit 2024 to 2027, no administrator rights. The engine behind every button has its own test suite; the Revit side is young, and the Check panel has a Report Bug button for a reason. Tell us what you find.

Download the beta Try the route demo