Short definition
Drip irrigation delivers water slowly at the root zone of plants through low-flow emitters along a small-diameter line. It uses 30–50% less water than spray sprinklers because almost none evaporates or runs off. In WA, the Saving Water Partnership pairs nicely with this — when you also install a WaterSense smart controller, the controller is rebate-eligible.
What it is
A drip-irrigation system runs water at low pressure (typically 25–30 psi) through a small-diameter polyethylene main line, with emitters spaced to match plants. Each emitter releases water at a measured rate — commonly 0.5 to 2 gallons per hour — directly onto the soil at the plant’s base. The result: water reaches roots, not air.
A standard residential drip system has these components:
- Backflow preventer at the supply tap — required by the Uniform Plumbing Code and WAC 246-290-490 cross-connection rules to keep landscape water from contaminating drinking water.
- Pressure regulator — full house pressure (typically 50–80 psi) blows out drip emitters; a regulator drops it to about 25 psi.
- Filter — drip emitters clog easily on sediment; a mesh or disc filter is required.
- Mainline poly tubing — usually ½-inch or ¾-inch.
- Drip lateral with emitters spaced for the plants in each zone.
- Optional smart controller — turns the system on and off based on weather and soil data.
End-of-season maintenance varies by region. In Eastern WA, blow out the lines before the first hard freeze. In Western WA, draining the low end is usually enough.
Why it matters to a homeowner
Western Washington’s dry season runs from about mid-June to mid-September — three months when established gardens still need water but spray sprinklers waste 30–50% of what they put out. Drip beats sprinklers on every metric except convenience: lower water bills, less foliage disease (no wet leaves), no overspray onto fences and walks, and no runoff onto pavement.
The catch is install effort. A retrofit drip system on a small garden takes a weekend and $150–$300 in materials. Pro install runs $500–$2,000 depending on zone count.
When a contractor says you need a “backflow preventer for the irrigation tie-in,” that’s not optional — it’s UPC and WA cross-connection rule. A pressure-vacuum breaker (PVB) on the supply is the typical residential install; expect $150–$400 in parts and labor.
Common failure modes
- Emitter clogging from minerals or sediment — Spokane and Eastside hard water shortens emitter life; pre-filter helps.
- Freeze damage to exposed lines — winterize per region; drain or blow out.
- Pressure regulator failure — emitters blow out one by one as upstream pressure rises.
- Filter bypassed during install — clog cascade through whole system.
- PVB freeze-split — exposed backflow preventers crack in freezes; insulate or remove for winter.
Washington note
The Saving Water Partnership (Seattle, Bellevue, Redmond, and other Cascade Water Alliance member utilities) offers a rebate for WaterSense-labeled smart sprinkler controllers — typically applied during the spring through fall window. The drip hardware itself isn’t directly rebated, but pairing drip with a smart controller stacks the savings: the controller cuts run time based on weather, and drip cuts the per-minute waste.
In Spokane and the Eastside on private wells, hard-water emitters clog faster — plan for a vinegar flush every season or install a softener upstream of the irrigation tap.
If your system needs a permit (most small drip retrofits don’t, but anything that ties into the supply main does), confirm the cross-connection requirement with your local water utility’s plumbing inspector. Verify the current Saving Water Partnership rebate amount and window at savingwater.org before committing — programs change year to year.