# Articles

*Browse all our published articles*

- [How to Account for Elevation Differences in Fire Hydrant Flow Tests and Water Supply Evaluations (NFPA 291)](/elevation-differences-hydrant-flow-tests-water-supply-nfpa-291) — Translate street-level hydrant pressures to design grade with field checks, 0.433 psi/ft math, and supply-curve shifts
- [How to Prepare and Use Diffusers and Dechlorinators in Fire Hydrant Flow Testing (NFPA 291)](/prepare-use-diffusers-dechlorinators-fire-hydrant-flow-testing-nfpa-291) — Keep pitot-based flow numbers valid while you control spray, runoff, and residual chlorine on the flow hydrant
- [Phase-Gate Safety Protocol for Fire Hydrant Flow Testing Under NFPA 291](/phase-gate-safety-protocol-fire-hydrant-flow-testing-nfpa-291) — Go/no-go controls, exclusion zones, and stop-work triggers mapped to every stage of the test
- [From Field Sheet to Audit File: Documenting and Archiving Fire Hydrant Flow Tests for NFPA 291, ISO & Design](/hydrant-flow-test-documentation-audit-file-nfpa-291) — A field-to-office workflow for complete data sheets, evidence packages, retention schedules, and handoffs that survive AHJ and ISO review
- [How to Select Residual and Flow Hydrants for Accurate NFPA 291 Flow Tests](/select-residual-flow-hydrants-nfpa-291) — A layout-first pairing method so residual and flow hydrants reflect true main capacity—not convenient nearby outlets
- [How to Calculate and Apply Friction Loss in Fire Hydrant Flow Tests and Water Supply Evaluations (NFPA 291)](/hydrant-flow-test-friction-loss-path-correction-nfpa-291) — Path-based pressure corrections from the residual hydrant to the design node
- [How to Determine and Apply the Correct Discharge Coefficient (C Factor) in Fire Hydrant Flow Tests (NFPA 291)](/hydrant-discharge-coefficient-c-factor-nfpa-291) — Field outlet identification, dual-coefficient pumper math, and how C errors scale available fire flow
- [How to Calculate Available Fire Flow from Hydrant Test Data: Formulas, Graphs & Worked Examples (NFPA 291)](/calculate-available-fire-flow-hydrant-test-data-nfpa-291) — Cross-check pitot, residual-curve, and rated-capacity paths so your 20 psi AFF holds up in design review
- [How to Graph and Interpret Fire Hydrant Flow Test Results: Residual Pressure Curves, Available Fire Flow & NFF Calculations (NFPA 291)](/hydrant-flow-test-graph-residual-pressure-curves-nff) — Build and read the residual-pressure curve so 20 psi available fire flow and NFF come off the plot—not only from formulas
- [How to Measure and Interpret Static, Residual, and Pitot Pressures in Fire Hydrant Flow Tests (NFPA 291)](/measure-interpret-static-residual-pitot-pressures-hydrant-flow-tests-nfpa-291) — Turn raw gauge readings into valid capacity data and system diagnostics
- [Main Capacity vs. Hydrant Capacity Flow Tests Under NFPA 291: Procedures, Differences & When to Use Each](/main-capacity-vs-hydrant-capacity-flow-tests-nfpa-291) — A use-case decision guide for multi-hydrant supply evaluation versus single-hydrant performance testing
- [How Often Should Fire Hydrants Be Flow Tested? NFPA 291, NFPA 25, AWWA M17 & Local Requirements Explained](/fire-hydrant-flow-testing-frequency) — A public-vs-private frequency decoder that separates annual operational flow from 5-year capacity tests across NFPA, AWWA, ISO, and AHJ rules
- [NFPA 291 Fire Hydrant Color Coding and Marking Guide: What the Colors Mean for Flow Capacity](/nfpa-291-fire-hydrant-color-coding-marking-guide) — Turn flow-test data into field-ready capacity colors crews can trust at a glance
- [Common Mistakes in Fire Hydrant Flow Testing and How to Avoid Them (NFPA 291)](/hydrant-flow-testing-mistakes-nfpa-291) — How field errors distort the Q formula, fake available fire flow, and cascade into sprinkler design and ISO failures—with NFPA 291 fixes
- [Applying Flow Test Results to Fire Sprinkler Design, Water Supply Evaluation & ISO Ratings](/applying-flow-test-results-sprinkler-design-iso) — A field-to-desk decision framework: turn hydrant readings into sprinkler go/no-go calls, pump triggers, ISO credit, and AHJ-ready packages
- [Essential Equipment Guide for Accurate Hydrant Flow Testing: Pitot Gauges, Kits, Diffusers & More](/hydrant-flow-test-equipment-accuracy-spec-guide) — Specify gear by the accuracy chain—not a catalog dump—so every static, residual, and pitot reading holds up
- [The Complete Step-by-Step Guide to Conducting a Fire Hydrant Flow Test (NFPA 291)](/nfpa-291-hydrant-flow-test-field-procedure) — A field-crew playbook for pairing hydrants, running the live sequence, and marking results to NFPA 291—without getting lost in calculator theory
- [Hydrant Flow Test Calculations Explained: Q Formula, Available Fire Flow, Examples & Free Calculator](/hydrant-flow-test-calculations-explained) — Convert pitot and residual readings into GPM and rated available fire flow with field-ready formulas