The Tri-Cities sprinkler blowout guide.
Timing, pressure limits, what the job should look like, and the KID wrinkle that costs people a mainline every year.
When to do it
First frost in the Tri-Cities usually lands somewhere between late September and mid October. The first genuine hard freeze, the kind that reaches down into shallow laterals, typically arrives in late October or early November. The widely used local rule is to be done by November 1 if your backflow preventer sits above ground, because that assembly is exposed and it freezes first.
The practical argument for going early is scheduling, not weather. Every irrigation and landscape crew in the valley is running the same six-week window. Book in late September and you pick your day. Book after the first freeze warning shows up on the forecast and you take whatever is left.
The Kennewick Irrigation District wrinkle
A large share of Kennewick, and pockets elsewhere, irrigate off KID rather than city water. KID runs a seasonal delivery calendar, and the district specifically asks that you not blow out your sprinklers until delivery has officially ended for the season.
The reason is simple. If there is still pressure behind your riser, air pushed into the system just gets replaced by water flowing back in the moment the compressor stops. You pay for a blowout and end up with a full system anyway, except now you believe it is empty. KID typically turns water back on around April 1.
Find out whether your irrigation comes from the city or from KID. If it is KID, confirm the season shutoff date first, then book. Any contractor worth hiring will ask you this before they quote.
Pressure limits, and why they matter
This is the part amateurs and cheap operators get wrong. What clears a zone is air volume, measured in CFM, not pressure. A small compressor cannot move enough volume, so the temptation is to crank pressure to compensate, which is how heads get destroyed and valve seals get cooked.
| Pipe type | Common max pressure | Notes |
|---|---|---|
| Rigid PVC | ~80 PSI | Most common in Tri-Cities residential laterals |
| Polyethylene (poly) | ~50 PSI | More flexible, less tolerant of pressure spikes |
| What clears the zone | CFM | Volume moves water out; pressure alone mostly makes noise |
A fair question to ask anyone quoting you: what CFM does your compressor put out? A crew doing this properly will answer without hesitating. A pancake compressor from a garage is not going to clear an eight-zone system in West Richland no matter how long it runs.
What a proper blowout looks like
- Supply is shut off and isolated before any air goes in
- Air is introduced at the backflow assembly or a dedicated blowout port
- Each zone is run individually, never all at once
- The zone runs until spray turns to mist, then to nothing
- A second short pass on each zone, because water beads back into the low points
- Manual drain valves opened where the system has them
- Controller set to off or rain mode, and the backflow assembly drained
On a typical Tri-Cities residential system, that is twenty to forty minutes of actual work. If someone is in and out in eight minutes on a ten-zone yard, you did not get a blowout, you got a visit.
Can you do it yourself?
Sometimes. If your system has manual drain valves at every low point and you know where all of them are, gravity draining works. Plenty of Tri-Cities systems, especially older central Richland installs, have no drain valves at the low points at all, and gravity will not empty those. Renting a compressor with real CFM output costs enough that the math usually favors just paying someone, and the downside of getting it wrong is a spring repair bill.
What it costs
Most Tri-Cities residential blowouts run roughly $55 to $140, driven mainly by zone count. Weigh that against a replacement system at several thousand dollars, or a single split mainline that means trenching through landscaping you already paid for.