Frequently asked questions — MEP Tools

Common questions about diameters, roughness, fitting K, pump power, and exporting.

Do I enter the nominal pipe size or the internal diameter?

The internal diameter (actual bore). The tool has no pipe-size or schedule tables, so it uses exactly the diameter you type. Look up the real internal diameter for your pipe material and schedule.

What happens if I leave roughness blank?

The tool assumes a smooth pipe (ε = 0) and shows a note saying so. Enter an absolute roughness (in mm, m, or in) to model a real wall.

Where do the fitting K values come from?

You supply them. There is no built-in fitting-K library — each row is your engineering assumption. Record where you got them in the source note field. The editor sums the rows into ΣK, which drives the minor-loss term ΣK·(v²/2g).

Why does transitional flow say the result is approximate?

Between Re 2300 and 4000 the flow is unstable between laminar and turbulent behaviour, and the tool applies the Swamee-Jain turbulent approximation there. The result panel adds a warning so you treat the number as indicative, not precise.

Why is shaft power showing a dash?

Shaft power needs a pump efficiency. Leave the efficiency field blank and only hydraulic power (P = ρgQH) is reported; enter an efficiency between 0 and 100 % to get an estimated shaft power.

Can I model zero flow?

Yes. Zero flow is valid — friction and minor losses become zero and the report shows only the static and residual head. A warning notes this.

How do I get a PDF report?

Two ways. Print (rail or File menu) opens your browser's print dialog — choose "Save as PDF" there — and is free on every plan, though the free copy carries a DRAFT watermark. Export PDF produces a branded PDF with your project header and no watermark; it is a Pro feature, and the action shows a pro badge and prompts an upgrade if your plan doesn't include it. See Saving, sharing & exporting and Plans & payments.

What does Share do?

Share (rail or File menu "Copy share link") copies a link that restores your entered values — including the fitting schedule — for whoever opens it. It does not share your saved project, and nothing is calculated on the other end until they press Calculate.

Why isn't there a result yet? Do I have to recalculate after every edit?

Yes. This tool never recalculates on its own — press Calculate to run the numbers. If you edit any field after a run, the result on screen is marked STALE until you press Recalculate (or Enter). See Getting started.

Do I need an account?

No account is needed to run the calculator — it's free and works for guests. You do need to be signed in to save, autosave, rename, or manage projects.

Is this an approved design or code check?

No. It is a preliminary, formula-only aid for a single pipe path. It does not check code compliance, pump selection, NPSH, surge, or manufacturer data. A qualified engineer must verify the final design — see Warnings & limits.