Getting started — MEP Tools

Walk through the five input stages, run Calculate, read the result panel, and share or export a report.

This tool computes a preliminary pressure drop and pump head for a single pipe path from inputs you provide. Nothing is calculated until you press Calculate — there is no live, type-as-you-go recompute.

Starting a calculation

A fresh document — and New from the File menu — opens with every field blank. Before your first run, a start panel appears above the input stages instead of a result:

• Describe the pipe run — fill in the five stages below yourself, or
• Load a worked example — fills a typical 25 mm pumped branch (1 L/s, 30 m, three seed fittings) and runs it immediately; the result is tagged EXAMPLE.

Either way, press Calculate — the button at the end of the action rail, or the Enter key — to run the numbers. This start panel shows whenever there is no result on screen yet; it is not gated by whether you are signed in.

The workflow

The input column is organised into five numbered stages. Fill them top to bottom; the result panel on the right updates on every change.

01 — Flow & pipe

The sizing basis for everything downstream.

• Flow rate — the design flow. Units: L/s, L/min, m3/h, m3/s, US gpm. Must be zero or greater. Zero flow is allowed and produces a static-only head (see Warnings & limits).
• Internal pipe diameter — this is the actual bore, not the nominal size. Units: mm, m, in. Must be greater than zero. Look up the real internal diameter for your pipe material and schedule; the tool has no pipe-size tables.
• Straight pipe length — the developed length of straight pipe on the path. Units: m, ft. Do not add equivalent lengths for fittings here — fittings are handled by the K method in stage 02.

02 — Loss assumptions

• Absolute roughness — pipe wall roughness ε. Units: mm, m, in. Leave it blank for a smooth-pipe assumption (ε = 0); the panel shows a "smooth-pipe assumption" note when it is empty.
• Fitting schedule — a list of fitting/valve loss coefficients (K). Each row has a label and a K value; Add fitting K appends a row and the trash button removes one. The editor sums them into ΣK, shown live at the bottom. A source note field records where your K values came from — fill it in, because these values are your engineering assumption, not a lookup.

03 — Pump head components

• Static / elevation head — the vertical lift the pump must overcome, in m or ft. A positive value is lift; a negative value means gravity assists the flow.
• Required residual pressure — the pressure that must remain at the outlet. Units: kPa, bar, mH2O, psi, Pa. Converted internally to a residual head of P / (ρg).

04 — Fluid & pump

• Density (kg/m³) and Dynamic viscosity (Pa·s) — fluid properties. Both must be greater than zero. Defaults are water at ≈20 °C (998.2 kg/m³, 0.001002 Pa·s).
• Pump efficiency (%) — used to estimate shaft power. Leave it blank to report hydraulic power only. If entered, it must be greater than 0 and at most 100.

05 — System schematic

A live sketch that redraws from the current velocity, bore, static head, and residual pressure. It is a visual sanity check, not an additional input.

Running the calculation

The action rail at the bottom of the page carries one primary button, whose label tracks the state of your last run:

• Calculate — shown before any run, or once required fields are filled in.
• Calculated — shown, disabled, immediately after a run with no further edits.
• Recalculate — shown once you edit any field after a run. The result on screen is now marked STALE, with a banner reading "Inputs changed. You're looking at the previous run." above it — press Recalculate (or Enter) to bring the displayed numbers back in sync with your edits.

Pressing Enter anywhere in the form triggers the same commit, except while typing in the fitting source-note field or when focus is already on a button or link (so it doesn't double-fire Calculate and whatever you just clicked).

Reading the result panel

The result panel leads with the headline number and a status chip, then expands into detail cards:

• Total pump head (hero, in metres) with the flow regime (Laminar / Transitional / Turbulent / No flow) — this tool makes no pass/fail judgement; Transitional is the only regime flagged as a caution, the rest are neutral.
• Four KPIs: Velocity (m/s), Pipe + fitting Δp (kPa), Hydraulic power (kW), and Shaft power (kW, or — when no efficiency is entered).
• Evidence cards you can expand: Head breakdown, Fittings and valves, Calculation steps, Assumptions and warnings, Formulas and references, and Report.

See Reading your result for what each card shows, and Methods & formulas for the equations behind every number.

Saving, sharing and exporting

• Save (Ctrl/Cmd + S, or the File menu) stores the project. You must be signed in to save and manage projects; the File menu shows a sign-in prompt otherwise. Autosave can be toggled on or off, and Save As / Rename manage named copies — see Projects & saving and Save status & unsaved work for how that works across the whole app.
• Share copies a link that restores your inputs for whoever opens it — nothing is calculated until they press Calculate.
• Print (free) and Export PDF (Pro) are two different report actions.
• New clears back to a blank document.

See Saving, sharing & exporting for the full detail on Share and the Print/Export PDF distinction.