Drip tubing sizing comes down to three numbers
Every inline drip tubing layout is a choice on three axes. Emitter GPH is how much water each outlet delivers per hour. Emitter spacing is how far apart the outlets sit on the tubing. Max run length is how many feet of tubing you can chain from one zone valve before pressure at the far end falls below the dripline's design point. Get any one wrong and the bed at the end of the line underwaters while the bed at the start drowns.
Soil type sets spacing. Plant water demand sets GPH. The dripline manufacturer's pressure-compensating range sets the run-length cap. The sections below walk each axis in order. Read top to bottom and end with a spec'd zone. Browse coils on the Inline Drip Tubing category.
Emitter spacing: match it to your soil's wetting cone
Emitter spacing follows the soil's wetting cone. Water leaving a drip emitter does not sink straight down. It spreads sideways as it falls, forming a roughly conical wet zone under the surface. The width of that cone is set by how fast the soil drains. Sandy soils drain fast, so water races down and sideways spread is narrow. Clay soils drain slowly, so water lingers in the upper profile and spreads broadly. Loam sits in the middle.
Spacing tighter than the wetting cone width buys nothing. The cones overlap and you paid for emitters you do not need. Spacing wider than the cone width leaves dry stripes between rows. The published rule of thumb:
Emitter GPH and plant water demand
Emitter GPH (gallons per hour) is the dial that controls how long the zone needs to run. Higher GPH means a shorter run time delivers the same volume of water. The constraint: every line of dripline runs on the same controller program, so the GPH has to match the slowest-drinking plant on the line. Mix high-demand annuals with low-demand drought-tolerant shrubs on one zone and the shrubs will rot.
Max run length: how far one inlet feeds
Max run length is set by pressure. Pressure-compensating dripline holds its rated GPH across an operating pressure band, typically 7 to 60 PSI for Netafim Techline CV and Rain Bird XFS-CV. Past the upper end of that band the emitters meter tighter. Below the lower end they meter under. Max run length is the longest stretch of tubing where the far end still sits inside the band given inlet pressure and friction loss along the run.
Per Netafim's Techline CV design guide, with published values for half-inch tubing at 40 PSI inlet, longer spacing buys longer allowable runs. Fewer outlets per foot mean less cumulative GPH draw per foot of tubing.
Pressure-compensating vs non-PC
Pressure-compensating dripline (Netafim Techline CV, Rain Bird XFS-CV) holds rated GPH across a wide inlet-pressure band, so emitters at the high point of a sloped run deliver the same volume as emitters at the low point. Non-PC dripline meters by simple orifice flow, so emitter GPH drops as pressure drops. The decision rule:
- Use PC dripline on any slope greater than about 5 ft of elevation across the run, on any run within 10% of the max-run table figure, and on any zone where uniformity matters (vegetable beds, formal plantings). PC is the default for new installs.
- Use non-PC dripline on short (under 100 ft), flat, residential beds where the cost savings show up and the uniformity penalty is negligible.
The standard residential PC choices on Total Sprinkler are root-resistant and reclaimed-water-rated. Netafim Techline CV 0.6 GPH at 18 in spacing (NET-58-1077) is the most-stocked low-flow option, best fit for shrub borders on loamy soil. The same 0.6 GPH at 12 in spacing (NET-58-1074) suits sandier soils where 18 in leaves gaps. Netafim Techline CV 0.9 GPH at 12 in (NET-58-1083) is higher flow for raised vegetable beds. Rain Bird XFS-CV 0.6 GPH and 0.9 GPH ship in 500 ft coils for larger zones. Browse every active coil on the Inline Drip Tubing category.
Fittings close the loop. An insert coupling (NET-58-1061) joins two coils end to end. A 3/4 in male adapter (NET-58-1058) ties dripline to standard PVC supply. A shut-off valve (NET-58-1097) lets you isolate a zone for repair without killing the whole controller program. Find them on the Drip Fittings category.
Spec the dripline, then build the zone
You have your GPH, spacing, and run plan. Grab pressure-compensating coils, emitters, filters, and regulators to finish the build.
