Irrigation
Sprinkler Installation in Kent & Greater Seattle
Quick answer
Sprinkler installation puts a zoned automatic watering system underground: mainline, valves, heads and a controller, plus the backflow assembly Washington requires at the point of connection. In the Puget Sound market a residential system typically runs $850 to $1,400 per zone installed, and most city lots need four to eight zones.
People move here and assume a yard in Seattle waters itself. Then they live through their first July. From about the Fourth of July to the middle of September this region gets almost nothing, and the lawn that was drowning in February goes crisp inside six weeks. A hose-end sprinkler on a dial timer covers for a while, right up until you travel for ten days. A fixed system runs at four in the morning before wind and evaporation take half of it, and it waters shrub beds on a completely different schedule than turf.
Every design we draw starts at the hose bib with a pressure gauge and a five-gallon bucket on a stopwatch. Static pressure and available flow decide everything downstream: how many heads can share a valve, whether rotors or MP Rotator nozzles make sense, and what the mainline has to be. Valley-floor lots in Kent and Auburn often read 70 psi with volume to spare. A hillside service in Newcastle or up above Issaquah can show 45 psi on a three-quarter-inch meter, and that yard gets a different zone count or it will never cover.
The backflow assembly is not a line item to shop on price. Washington cross-connection rules require an irrigation system to be isolated from the drinking water supply, which in practice means a double check valve assembly or a pressure vacuum breaker at the point of connection, installed under your water purveyor and tested by a state-certified assembly tester before the system is considered done. Kent, Covington Water District, Soos Creek and Highline all want that first report on file, and they follow up when it does not arrive.
We draw the plan in our own office and dig the trenches with our own crew. Nothing gets handed to a sub on a system that will sit buried under your lawn for the next twenty years, because the person who set the head height is the person you call when it sinks. In loose valley loam a vibratory plow pulls pipe with almost no scarring. Up on the plateau in Alderwood till the plow skips off hardpan, so we trench and build the turf restoration into the schedule instead of leaving you a striped yard.
What’s included
- Static pressure and flow test at the point of connection, measured with a gauge and a timed bucket fill before any layout is drawn
- Zone plan produced in-house that separates turf from beds, sun from shade, and slope from flat ground so nothing shares a valve it should not
- Head layout at head-to-head spacing with matched-precipitation nozzles inside every zone
- Mainline tap, isolation valve and backflow assembly installed to your water purveyor requirements
- Trenching or vibratory plowing with laterals set 8 to 12 inches deep and mainline below that
- Valve manifolds in accessible boxes over a gravel sump, wired in direct-burial multi-strand with waterproof splices
- Drip tubing and emitters for shrub beds and containers on their own zone, with an inline filter and pressure regulator
- Wi-Fi controller mounted, programmed by hydrozone and paired to a rain sensor or live weather feed
- Certified backflow test with the report filed to the purveyor, turf restoration, and a controller walkthrough before we hand it over
Materials we use
- Hunter PGP Ultra and I-20 rotors for open turf, Pro-Spray bodies for tight corners
- Rain Bird 1800-PRS spray bodies with pressure-regulating stems and check valves
- Hunter MP Rotator nozzles for matched precipitation on odd-shaped lawns
- Febco 765 pressure vacuum breakers and Watts 007 double check valve assemblies
- Hunter Hydrawise Pro-HC and Rain Bird ESP-TM2 Wi-Fi controllers with rain sensors
- Class 200 PVC mainline with flexible polyethylene laterals and insert fittings
- Netafim Techline and Rain Bird XFS inline dripline with 25 psi regulators and Y-filters
- Direct-burial 18-gauge multi-strand wire with DBR/Y waterproof splice connectors
How the build runs
- Step 1
Walk the yard and test the water
We start with the meter and the hose bib. Gauge on, bucket timed, meter size and service line material noted. Then we walk the property looking at sun exposure, slope, existing planting and where the dog runs. That hour decides whether the yard is a four-zone job or a nine-zone job, and it is the difference between a system that covers and one that leaves a brown arc every August.
- Step 2
Draw the zones in-house
The plan comes off our own desk, not a supplier catalog. Turf gets rotors or MP Rotators; beds get dripline; anything on a south-facing slope gets separated from the flat shady side of the house because it will need twice the run time. Zone flow is kept under about 75 percent of measured capacity so the last head on the line still throws its full radius.
- Step 3
Locate utilities and open the ground
A public locate ticket goes in before a shovel moves, and we hand-pothole around gas services and unmarked private lines like the run to a detached garage. Loose soil gets vibratory plowed. Till and rocky ground gets trenched with a walk-behind. Sod is cut and rolled where we can save it, and the spoils are kept on boards so the lawn does not end up buried in subsoil.
- Step 4
Set the point of connection and the backflow
We tap the domestic line downstream of the meter, add a brass isolation valve so the whole system can be shut off without killing water to the house, and set the backflow assembly at the height the code requires. Pressure vacuum breakers go a foot above the highest head. Double checks get a drainable box. The assembly is placed where a tester can reach it and where a freeze cover fits.
- Step 5
Assemble heads, valves and wire
Laterals get glued or clamped, heads go on swing joints so a mower strike bends the joint instead of snapping the pipe, and every head is set flush with finish grade rather than proud of it. Valves land in one or two manifolds instead of scattered singles, which keeps future service to one box. Wire runs with the mainline, with a spare conductor pulled to every manifold.
- Step 6
Flush, program and tune the coverage
Zones get flushed before nozzles go in so glue chips and grit do not park in a screen. Then the controller is programmed by hydrozone with cycle-and-soak splits on heavy ground, and we run every zone while watching it. Arcs get set, radii get adjusted, and any head that is throwing onto the driveway or the neighbor fence is re-nozzled on the spot.
- Step 7
Certify, restore and hand it over
A certified tester runs the assembly and the report goes to your water district. Trenches are backfilled, tamped and either re-sodded or seeded, and we come back to top-dress any settling. Last, we sit at the controller with you, show the seasonal adjust, the rain sensor bypass and the master shutoff, and leave a zone map taped inside the cabinet door.
A four to six zone residential system is normally 2 to 4 days on site; larger properties, long mainline runs and drip conversions push to 4 to 7 days, with the certified backflow test scheduled inside the following week.
What it costs
Real installed ranges for the Puget Sound market, published so you can plan before anyone visits.
| Item | Typical range | Unit |
|---|---|---|
| Residential system, typical per-zone costIncludes heads, lateral, valve, wire and trenching for that zone | $850-$1,400 | per zone |
| Complete 5-zone system on an average city lot | $4,800-$8,400 | installed |
| Backflow assembly, purveyor paperwork and first certified testPVB at the low end, a vaulted double check assembly at the high end | $750-$1,700 | installed |
| Dripline zone for shrub beds, with filter and regulator | $500-$1,100 | per zone |
| Wi-Fi controller with rain sensor | $425-$950 | installed |
| Open turf coverage on larger lotsUnit cost drops as zones get bigger and obstacles get fewer | $0.70-$1.20 | per irrigated sq ft |
These are typical installed ranges for the Puget Sound market in 2026 rather than a quote, because measured pressure, meter size, soil type and how far the point of connection sits from the far corner of the yard move the number more than square footage does, and all four get confirmed during a site walkthrough.
Building this in the Pacific Northwest
Where the water goes when the zone shuts off
Every head below the elevation of its valve will drain the lateral out through itself after each cycle. On a sloped Renton or Newcastle lot that means the bottom head weeps a puddle twice a day all summer and a soggy patch that never dries. We spec check valves in the head bodies on any zone with more than a couple of feet of fall. Valve boxes get a gravel sump underneath, because on the Kent and Auburn valley floor the winter water table can sit high enough to fill an unbedded box and leave the solenoids submerged for months.
Trenching and watering glacial till
Above the valley, Alderwood and Everett series soils put a cemented hardpan layer within a couple of feet of the surface. It stops a vibratory plow dead, so those yards get trenched and priced accordingly. The same hardpan changes how the system has to run: water applied faster than about a third of an inch per hour sheets downhill off compacted till instead of soaking in, so we build cycle-and-soak schedules into the controller and hold zone precipitation rates low rather than trying to finish a zone in one long run.
Designing for a freeze you will forget about
Winters here are mild until an east wind event drops us below freezing for four or five days in December or January. The first casualty is always an above-grade pressure vacuum breaker with water still in the bonnet. We locate the assembly where an insulated cover actually fits, put a drainable isolation valve ahead of it, and add a blowout port so the whole system can be cleared with compressed air in the fall. A system designed without that port costs more to winterize every single year.
Permits, purveyors and the annual test
No building permit is needed for the sprinkler system itself anywhere in King County. The backflow assembly is a different matter: it falls under WAC 246-290-490 cross-connection control, so your water purveyor has to be notified, the assembly has to be an approved model installed at the correct orientation and height, and a Washington-certified backflow assembly tester has to pass it on installation and again every twelve months. Some districts, including Covington Water District and Soos Creek, will also quote you a separate irrigation meter, which usually pays for itself by keeping summer watering off your sewer volume charge.
Sprinkler Installation: common questions
How many zones will my yard need?
Zone count comes from available flow, not lot size. A typical 6,000 square foot city lot in Kent or Burien with a front and back lawn and two bed areas usually lands at four to six zones. A half-acre in Maple Valley with a slope and mature planting is more often seven to ten. If your service reads low pressure, the same yard needs more zones with fewer heads on each, which raises the total.
Do I actually have to install a backflow preventer?
Yes. Washington cross-connection control rules treat every lawn irrigation system as a health hazard to the potable supply, because a pressure drop in the main can pull fertilizer-laden standing water backward out of your pipes. Your water purveyor requires an approved assembly, correctly installed, tested at installation and retested annually by a certified tester. Skipping it can get your water service shut off, and it makes any future home sale inspection awkward.
Will you tear up my lawn to put it in?
Less than you expect. A vibratory plow slices a narrow slit and pulls the pipe through it, which leaves a seam that closes over in two or three weeks of growth. Where soil is too hard or too rocky to plow, we trench a four-inch wide cut, keep the sod in rolls and lay it back down the same day. Either way we return to top-dress settled lines once the ground has taken its first rain.
What is the best time of year to install a system?
March through June is the sweet spot. The ground is workable, sod and seed take hold quickly, and the system is commissioned before the dry stretch starts. September and early October also work well and often have better scheduling. We install through the winter when soil conditions allow, but saturated clay compacts badly under equipment, so on wet valley lots we would rather wait a few weeks than leave you with ruts.
Can the same system water native and drought-tolerant beds?
It should, but not on the same valve as the lawn. Sword fern, salal, kinnikinnick and evergreen huckleberry need deep infrequent water while they establish and then very little. Putting them on lawn spray heads either drowns them or trains shallow roots. We run those beds on their own dripline zone at a low emitter rate, then dial the run time back sharply after the second summer once the plants are rooted.
How much will it add to my water bill?
A well-designed system usually costs less than hand watering, because it applies water at the rate the soil accepts it and it runs before sunrise. On an average Kent lot expect roughly $40 to $90 a month across the three genuinely dry months, and close to nothing the rest of the year. A weather-based controller and a rain sensor typically shave another 20 to 30 percent off that.