Design & sizing
How many zones, GPM math, head spacing, transformer VA, and pipe sizing basics.
How do I calculate irrigation zone GPM?
Add the GPM of every head/nozzle on the zone at the design pressure (from nozzle charts). That sum is the zone demand. Confirm the water source and pipe can supply it with acceptable pressure loss. If demand exceeds supply, split into more zones.
How many sprinkler heads per zone?
There is no fixed number—limit by total GPM and matched precipitation. A zone might have 4 large rotors or 12 small sprays. Keep precipitation rates matched and pressure adequate at the farthest head.
What pipe size should I use for irrigation laterals?
Size pipe so water velocity stays reasonable (often under ~5 ft/s) and friction loss leaves enough pressure at heads. Many residential laterals use ¾" or 1" PVC/poly; larger mains feed manifolds. When in doubt, upsize—the material cost is small versus digging twice.
How do I measure household water pressure for irrigation?
Attach a pressure gauge to a hose bib, note static psi with no flow, then note residual pressure while a known load runs if possible. Design from residual pressure available during watering, not just static.
What is precipitation rate in irrigation?
Precipitation rate is inches per hour applied by a zone. It lets you convert plant water need (inches/week) into run minutes. Nozzle charts and catch-can tests measure it.
Should irrigation zones separate sun and shade?
Yes when possible. Shade needs less water than southern exposures. Mixing them forces you to overwater shade or underwater sun.
How do I design irrigation for a slope?
Use lower precipitation nozzles (MP Rotator), cycle-and-soak, check valves, and lateral layouts that avoid dumping at the bottom. Drip is often better for sloped planting beds.
What is head-to-head coverage?
Each head’s spray should reach the neighboring heads so coverage overlaps. Gaps between radii create brown spots even if runtimes are long.
How much water does a lawn irrigation system use?
It depends on climate, soil, and precipitation rate. Calculate zone GPM × runtime minutes × cycles per week. Smart controllers and seasonal adjust can cut use substantially versus fixed summer schedules.
Can I irrigate from a well or pump?
Yes with a properly sized pump, pressure tank or pump start relay, and filtration. Protect the pump from rapid cycling and dry run. Confirm water quality for drip emitters.
What backflow preventer do I need for irrigation?
Local code dictates —often a PVB or RPZ for potable connections. Install at the required height, protect from freezing, and test annually where required. Never omit backflow on a potable tap.
How do I size a mainline for multiple valves?
Size for the largest simultaneous flow the controller might run (usually one zone at a time on residential). Commercial multi-station setups need mainlines for stacked flow—design deliberately.
What is the difference between static and dynamic pressure?
Static is pressure with no flow; dynamic (residual) is pressure while water moves. Heads care about dynamic pressure at the nozzle during operation.
Can a typical residential irrigation system supply 5 GPM?
Some homes can deliver about 5 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 5 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 8 GPM?
Some homes can deliver about 8 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 8 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 10 GPM?
Some homes can deliver about 10 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 10 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 12 GPM?
Some homes can deliver about 12 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 12 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 15 GPM?
Some homes can deliver about 15 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 15 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 20 GPM?
Some homes can deliver about 20 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 20 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 25 GPM?
Some homes can deliver about 25 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 25 GPM. Split zones if the source cannot keep pressure at the heads.
Can a typical residential irrigation system supply 30 GPM?
Some homes can deliver about 30 GPM at usable pressure; many cannot. Meter size, service line length, elevation, and indoor demand all matter. Measure flow with a timed bucket test or gauge kit before designing large rotor zones that assume 30 GPM. Split zones if the source cannot keep pressure at the heads.
What does Hunter PGP stand for?
PGP is Hunter’s classic gear-driven rotor line used widely on residential and light commercial turf. Modern variants such as PGP Ultra continue that platform with updated nozzles and features.
What is a Hunter Pro-Spray body?
Pro-Spray is Hunter’s spray sprinkler body line that accepts threaded nozzles (including MP Rotator). Bodies vary by pop-up height and pressure-regulation options.
What is an FX Luminaire Luxor system?
Luxor is FX’s lighting control platform for zoning and dimming compatible FX fixtures. It is a design choice for properties that want scenes beyond a simple photocell.
What is a solenoid adapter used for?
Adapters let you fit a replacement solenoid onto a valve body when threads or heights differ between brands or generations. Match the adapter to both the valve and solenoid specifications.
What is a swing joint in irrigation?
A swing joint is a flexible pre-assembled pipe link under a sprinkler head that absorbs traffic loads and simplifies grade adjustments. It reduces broken fittings versus rigid risers.
How do I separate turf and shrub irrigation zones?
Put turf sprays/rotors on their own valves and shrubs on drip or matched bed zones. Different plant types almost never share a happy runtime.
What is a catch-can test?
Place identical containers across a zone, run a timed cycle, measure water depth in each can, and map uniformity. It is the ground-truth check for coverage.
How do I design around a septic drain field?
Avoid spray irrigation on drain fields where prohibited. Use drip carefully only if local health codes allow, and keep spray overspray off the field.
Should irrigation pipes be PVC or polyethylene?
Both are common: PVC for rigid mains/manifolds, poly for flexible laterals. Follow local practice, UV rules, and fitting systems—do not mix incompatible solvents/barbs.
How much slope is too steep for spray irrigation?
Steep slopes need low precip rates, cycle-and-soak, and often drip for plantings. If runoff leaves the zone in minutes, redesign nozzles and scheduling before adding runtime.
What is hydrozoning?
Grouping plants with similar water needs on the same valve. It is the foundation of efficient design and beats any smart controller on a bad zone map.
How do I account for elevation in irrigation design?
Elevation changes pressure (~0.433 psi per foot of water column). Uphill heads see less pressure; downhill lines may need check valves for drainage control.
Can I irrigate pots on a drip zone with in-ground shrubs?
Only if water needs and schedules align—pots dry faster. Prefer a dedicated container drip zone or separate timer valve.
How should I design irrigation zones at 20 psi?
At about 20 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Favor nozzles rated for lower pressure and avoid long rotor throws that need higher psi. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 25 psi?
At about 25 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Favor nozzles rated for lower pressure and avoid long rotor throws that need higher psi. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 30 psi?
At about 30 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Favor nozzles rated for lower pressure and avoid long rotor throws that need higher psi. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 40 psi?
At about 40 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Verify residual pressure under flow; static pressure alone can mislead. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 50 psi?
At about 50 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Verify residual pressure under flow; static pressure alone can mislead. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 60 psi?
At about 60 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Consider pressure regulation to reduce misting and wear. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 70 psi?
At about 70 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Consider pressure regulation to reduce misting and wear. Recheck GPM totals after nozzle selection.
How should I design irrigation zones at 80 psi?
At about 80 psi at the head, select nozzles/rotors whose charts list performance at that pressure—do not assume catalog radius at a different psi. Consider pressure regulation to reduce misting and wear. Recheck GPM totals after nozzle selection.