# Getting started

Source: https://meptools.com/tools/water-pipe-pressure-drop-pump-head/docs/getting-started/

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:

![Water pipe calculator's blank start panel above the empty input stages](./_assets/water-pipe-start-zone.png)

- **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](/tools/water-pipe-pressure-drop-pump-head/docs/warnings-and-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:

![Water pipe calculator's worked-example result: headline pump head, regime chip and the KPI row](./_assets/water-pipe-result-panel.png)

- **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](/tools/water-pipe-pressure-drop-pump-head/docs/results) for what each
card shows, and [Methods & formulas](/tools/water-pipe-pressure-drop-pump-head/docs/methods) 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](/docs/projects) and [Save status & unsaved work](/docs/save-status) 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](/tools/water-pipe-pressure-drop-pump-head/docs/exporting-and-saving)
for the full detail on Share and the Print/Export PDF distinction.