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The rated discharge of a single emitter at the design pressure.
Take it from the dripline's published data at the pressure the regulator will actually deliver, not at the pressure printed at the top of the table. Pressure-compensating dripline holds its rate across a range and non-compensating dripline does not, which matters on any lateral with a fall along it.
The distance between emitters moulded into the tube.
This is fixed by the product, not chosen on site — dripline is manufactured with its emitters at a set interval and the interval is part of the part number. Closer spacing suits lighter soils where the wetted bulb is narrow; wider spacing suits heavy soils where water spreads laterally before it drains.
The distance between adjacent runs of dripline across the planting.
This is the one spacing you control, and it is what turns a fixed product into a chosen application rate. Laterals set at the same interval as the emitters give a square grid and the most even wetting; wider intervals apply less depth per hour but leave dry ribbons between the runs on soils that do not spread water sideways.
Application rate
0.415 in/h
This is the rate the grid applies over the area it covers, which is the number a controller needs. It is not a statement about what reaches the root zone: on a slope, on a crusted soil, or with an emitter that has begun to plug, the applied depth and the infiltrated depth part company.
- Area served by each emitter
- 1.63 ft²
- Discharge per unit length of lateral
- 0.43 gal/h/ft
- Depth applied in a thirty-minute run
- 0.21 in
They open the calculator with your figures already in it
Dripline Precipitation Rate Calculator: 0.4155 in/h — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- ASABE/ICC 802, Landscape Irrigation Sprinkler and Emitter Standard — provides the reference frame under which emitter discharge is published, which is the figure this calculation depends on
- Application rate = emitter discharge ÷ (emitter spacing × lateral spacing). One litre per hour spread over one square metre is one millimetre of depth per hour, by definition of the litre
Inputs used
- Emitter Discharge
- 0.42 gal/hr
- Emitter Spacing Along the Lateral
- 11.75 in
- Spacing Between Laterals Across the Bed
- 20 in
Intermediate steps
- Area served by each emitter
- 1.63 ft²
- Discharge per unit length of lateral
- 0.43 gal/h/ft
- Depth applied in a thirty-minute run
- 0.21 in
Confidence note: This is the rate the grid applies over the area it covers, which is the number a controller needs. It is not a statement about what reaches the root zone: on a slope, on a crusted soil, or with an emitter that has begun to plug, the applied depth and the infiltrated depth part company.
What this calculation does not cover
- Assumes every emitter on the zone is discharging at its rated figure, which requires the filtration and pressure regulation a drip valve should have at its head.
- Says nothing about run length. A lateral longer than the manufacturer's maximum loses pressure along its length, and the far end applies less than this figure whatever the label says.
- Ignores evaporation from the surface between emitters, which for surface-laid dripline in an exposed bed is not negligible.
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This result is a specification — 0.415 in/h — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-08-30 · in the site-wide review of 2026-09-06 · v1.0.0
Regulatory standards & verification citations2
- ASABE/ICC 802, Landscape Irrigation Sprinkler and Emitter Standard — provides the reference frame under which emitter discharge is published, which is the figure this calculation depends on
- Application rate = emitter discharge ÷ (emitter spacing × lateral spacing). One litre per hour spread over one square metre is one millimetre of depth per hour, by definition of the litre
Which documents these citations point at
Standards referenced: ICC 802 (International Code Council, United States).
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