Sprinkler System Glossary

Pressure in your supply line. A typical home has 40-65 PSI static (no water flowing). Sprinklers need at least 25-30 PSI at the head to spray properly. Below 30 PSI you should use MP rotators or rotors instead of fixed sprays.

The volume of water available. A typical residential 3/4" service can deliver 8-15 GPM. Each sprinkler head uses some — usually 0.5 to 4 GPM. Sum of head GPMs in a zone must be less than your available flow.

The PSI you read on a gauge when no water is flowing inside the house. Measure with a $10 gauge screwed onto an outdoor faucet.

PSI at the sprinkler head while the zone is operating. Always lower than static pressure because friction in the pipes eats some. The longer the pipe and the more GPM flowing, the bigger the drop.

One valve controls one zone. All heads in the zone share the same available GPM, so we group them so the total stays within supply limits. A typical 5,000 sq ft yard has 3-6 zones.

An electric solenoid valve that opens when the controller energizes it. Mounted in a buried valve box near the supply tap. Rain Bird 100-DV and Hunter PGV are the home-DIY standards.

A timer that opens each zone valve in sequence. Pick zone count slightly higher than you need. Smart Wi-Fi controllers (Rachio, Hunter Hydrawise) cost more but cut water bills 20-40% by skipping watering days based on local weather.

Best for small-to-medium areas under 18 ft of throw. High precipitation rate (1-2 in/hr) means short run times but can cause runoff on clay soil. Rain Bird 1800 series is the industry standard.

Throws a single stream that rotates back and forth. Best for areas with 20+ ft of coverage. Lower precipitation rate (~0.4 in/hr) means longer run times but uniform soaking.

Multiple thin rotating streams. Lower precipitation rate (~0.4 in/hr) like a rotor, but works at smaller radii like a spray. Best choice for medium-pressure systems or areas with mixed sun/shade. Hunter MP1000, MP2000, MP3000.

Inches per hour the zone delivers to the soil. Used to compute run time: target inches ÷ rate = hours. Sprays are 1-2 in/hr, rotors are 0.3-0.5 in/hr. All heads in one zone should have similar rates ("matched precipitation rate" or MPR).

A best practice: every head in a zone delivers water at the same in/hr regardless of arc. Manufacturers achieve this by varying nozzle flow with arc — a 90° nozzle uses 1/4 the GPM of a 360° at the same precip rate. Hunter MP rotators are specifically built for MPR.

In degrees: 90° corner, 180° edge, 360° full circle. Most heads have adjustable arcs; some are fixed. Corner heads get 90°, edge heads get 180°, interior heads get 360°.

Required by code in most jurisdictions. Two common types: Pressure Vacuum Breaker (PVB, installed above ground, simpler) and Reduced Pressure Zone (RPZ, more robust, sometimes required in stricter codes). Always check with your local water utility.

A short length of flexible "funny pipe" with threaded ells that lets a head pivot if a mower hits it, and lets you fine-tune the height. Cheap insurance — use one at every head.

Always under pressure. Typically 1" Schedule 40 PVC. Runs from your backflow preventer to the valve manifold.

Only pressurized when that zone is running. Typically 3/4" Schedule 40 PVC. One lateral system per zone.

The gold standard for uniform watering: space heads so each one's radius reaches the next head. Doubles up coverage, eliminates dry patches. This is what "Standard" coverage in our designer targets.

On clay soil or steep slopes, water runs off before the soil absorbs it. Split a 20-minute run into two 10-minute cycles 30 min apart. The soil soaks in during the rest period.

The threaded outdoor spigot. You attach a hose to it — but you can also tap it for a sprinkler system if you don't want to cut into your main supply.