What each validation error and calculation warning means, and the boundary of what this tool certifies.
The tool reports two kinds of feedback: validation errors that block a result, and calculation warnings that annotate a result you can still read. This page explains both and the scope boundary you must respect.
If any input fails its rule, the result panel shows the message(s) below instead of a report:
| Message | Cause |
|---|---|
| Flow rate must be zero or greater. | Negative or non-numeric flow. |
| Internal pipe diameter must be greater than zero. | Diameter ≤ 0 or blank. |
| Pipe length must be zero or greater. | Negative length. |
| Absolute roughness cannot be negative. | Negative roughness (blank is fine — it means smooth). |
| Static head must be a number. | Non-numeric static head (blank is fine; negative is fine — it means gravity assists the flow). |
| Density must be greater than zero. | Density ≤ 0. |
| Dynamic viscosity must be greater than zero. | Viscosity ≤ 0. |
| Required residual pressure cannot be negative. | Negative residual pressure. |
| Pump efficiency must be greater than 0 and at most 100%. | Efficiency out of the 0–100 range. |
Fitting K must be zero or greater: <label>. | A fitting row has a negative K. |
These appear in the Warnings & assumptions card. Informational notes (.) confirm an
assumption; warnings (!) flag something to check.
| Level | When it appears | Meaning |
|---|---|---|
| Info | Always | Formula-only preliminary calculation — no material, roughness, fitting-K, pipe-size, or fixture-unit tables are embedded. |
| Info | Roughness left blank | Using the smooth-pipe assumption (ε = 0). |
| Info | ΣK = 0 | No fitting/valve minor losses were included. |
| Info | Static head is negative | Gravity assists the flow. |
| Warning | Flow = 0 | Zero flow: friction and minor losses are zero; only static/residual head is shown. |
| Warning | 2300 ≤ Re ≤ 4000 | Transitional flow: the result is approximate and may be unstable between laminar and turbulent behaviour. |
| Warning | Total head ≤ 0 | A pump may not be required for these assumptions — verify the system hydraulics. |
This is an independent preliminary engineering aid for a single pipe path. It does not verify or account for any of the following:
Pipe roughness and fitting K are user-entered assumptions, and the tool does not certify their suitability. Final design must be verified by a qualified engineer against the adopted codes, project specifications, manufacturer data, and the authority having jurisdiction. Treat the report as a transparent preliminary calculation — not an approved design, a code-compliance check, or a pump selection.
See also Inputs & units for the per-field rules and Methods & formulas for what each number means.