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Sample inputs and outcomes
| Scenario | Method | Key inputs | Typical output |
|---|---|---|---|
| Subdivision roadway | Linear | Road 450 m, spacing 90 m, offset 15 m | ~6 hydrants, achieved spacing ~84 m |
| Industrial plot | Grid | Site 300 m × 180 m, spacing 60 m, radius 75 m | 6 × 4 grid, 24 hydrants, dx ~60 m |
| Compact site | Grid | Site 120 m × 80 m, spacing 75 m, radius 50 m | 3 × 3 grid, 9 hydrants, dx ~60 m |
These rows are examples for planning discussions, not code requirements.
How spacing and counts are estimated
- Usable = L − 2E
- N = ceil(Usable / S) + 1 (minimum 2)
- ActualSpacing = Usable / (N − 1)
- Stations: E, E+ActualSpacing, … , L−E
- GridSpacing = min(S, 2R)
- Nx = ceil(L / GridSpacing) + 1
- Ny = ceil(W / GridSpacing) + 1
- dx = L / (Nx − 1), dy = W / (Ny − 1)
Practical steps for a better placement plan
- Pick your unit system and choose a layout method.
- Enter road length for linear, or site length and width for grid.
- Set max spacing and coverage radius for your planning basis.
- Use end offset if hydrants cannot sit at endpoints.
- Click Calculate to see spacing, counts, and placement rows.
- Download CSV for CAD/GIS inputs, or PDF for reviews.
Service area and access distance
Hydrant spacing is usually driven by response access and hose lay distance. Planning targets often land between 60–150 m (about 200–500 ft) depending on hazard level, road layout, and local requirements. This calculator helps you test those targets quickly by converting your inputs into a consistent spacing plan, plus a count you can budget for. Shorter spacing can improve coverage where buildings are dense and access is limited.
Linear corridor planning
For a road, utility corridor, or main extension, spacing works best when it is predictable for crews and maintenance. The linear method subtracts end offsets, then divides the usable length into equal segments. The output “achieved spacing” shows what your project actually delivers once the count is rounded to whole hydrants, which is what procurement needs. Use the station list to align hydrants with curb lines, crossings, and future tie-ins.
Site grid planning and redundancy
For campuses, industrial parcels, and large plots, a simple grid is a fast first pass. The grid method chooses a target spacing based on the tighter of your max spacing and 2×coverage radius. This supports overlap between hydrants so that a single obstruction or access issue does not isolate an area, especially near corners and long façades. If your site has internal roads, adjust dimensions to reflect drivable routes rather than straight-line distances.
Hydraulic considerations and testing
Spacing alone is not sufficient; water supply must support flow and residual pressure at the hydrants you propose. Use the placement list to coordinate pipe sizing, valve locations, and looping for reliability. After installation, routine flow testing and maintenance keep hydrants available, reduce debris risks, and confirm performance under demand. Record test dates for audits.
Documentation and coordination
Treat this output as a planning worksheet. Export CSV to share coordinates or stations with CAD/GIS, and export PDF for design reviews. Then coordinate with the utility, civil team, and the authority having jurisdiction for setbacks, accessibility, signage, and conflict checks with driveways, utilities, and turning radii.
FAQs
1) What is the difference between max spacing and coverage radius?
Max spacing is the layout limit you want to meet. Coverage radius is a planning distance for reach. The grid method uses 2×radius as an overlap check.
2) Why does the achieved spacing change after I calculate?
Hydrants must be a whole number. The calculator rounds the count up, then redistributes spacing evenly. Achieved spacing is the true spacing your plan delivers.
3) When should I use an end offset?
Use it when endpoints are unsuitable, such as intersections, cul-de-sacs, or private access points. Offsets move the first and last hydrants inward while keeping spacing consistent.
4) How do I read the grid result (Nx × Ny)?
Nx is the number of hydrant points along site length, and Ny along width. Total hydrants equals Nx multiplied by Ny, with dx and dy showing the achieved spacing.
5) Can I switch between meters and feet?
Yes. Select your unit system before calculating. The calculator converts internally, then displays results in your chosen unit for consistent tables and exports.
6) What should I verify before finalizing placement?
Confirm local code criteria, water supply capability, vehicle access, and clearances from utilities. Coordinate exact locations with the utility and fire authority before construction documents are issued.