When to Close Your Pool in Pasco, WA: Deadline, Window & Checklist

Pasco closing dates at a glance

A classic four-season pool calendar: open early into cold water, close late into cold water, and Pasco's 107 days of prime swimming sit safely in between.

The same model in water terms: Pasco's estimated pool temperature runs about 51°F in mid-April, 67°F in mid-June, 74°F in mid-August, and 55°F in mid-October, peaking near 76°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.

The 12-step Pasco winterizing checklist

A closing is a plumbing project with a chemistry warm-up. Start a few days ahead of your target date, keep every dose per its product label, and don't skip the photographs — spring-you reassembles from them.

1. Balance the water a few days ahead

   Give the chemistry a head start — balance to label ranges several days out, while circulation can still mix corrections evenly. Closing-day dosing never distributes as well.

2. Deep-clean the pool

   Brush, skim, and vacuum like company's coming. A pool that goes under the cover spotless comes out needing a rinse; one that goes under dirty comes out needing a project.

3. Service the filter one last time

   Send the filter into winter clean: backwash the sand or DE, rinse and dry the cartridges indoors. Media stored dirty over winter hardens into a spring problem no backwash fixes.

4. Apply winter chemicals per label

   Winter chemicals go in before shutdown, not after: label-dosed, circulated for a few hours, distributed evenly. A floater dropped on still water protects one corner.

5. Lower the water level

   Drop the level as your cover manufacturer specifies — typically below the skimmer mouth for solid covers. Never drain a pool fully; groundwater pressure can damage the shell.

6. Blow out the lines and plug returns

   Work line by line: push air until the return spits dry mist, plug it against the flowing air, move on. Skimmer, returns, cleaner line, in whatever order your plumbing prefers — dry pipes are the entire point of closing.

7. Protect the skimmer

   Give the skimmer something cheap to break: a guard bottle or rated plug absorbs the ice expansion that would otherwise split the housing.

8. Add pool antifreeze where blowouts fall short

   Antifreeze is the insurance policy for doubtful lines, not a replacement for the blowout: pool-grade product, label dosing, and only where air couldn't finish the job.

9. Drain the equipment

   Every vessel on the pad — pump, filter, heater, chlorinator — gets its drain plugs pulled. Drop all the plugs in the pump basket; that's the one place everyone looks first in spring.

10. Set the air pillow and cover

    Pillow first, cover second, tension last. A properly centered pillow turns the winter ice sheet from a wall-pressing ram into a harmless dome.

11. Note this year's dates

    Jot down when Pasco's water actually cooled and when you closed. A two-line note beats memory next September 24 — your own yard runs a few days off any model, including ours.

12. Winterize the water features

    Waterfalls, slides, and spillover spas hold water in places gravity won't clear — blow those lines separately and plug them, or they'll be the one crack you find in spring.

What to buy before the rush

A small stack of supplies turns the checklist above into a single-weekend job. Buy before Pasco's September rush and the whole list ships at leisure instead of sprinting.

• Winter cover

  Measure with overlap; the winter workhorse over everything else.

• Cover pump

  Standing water is a cover killer; this is the counter.

• Expansion plugs + skimmer guard

  Cheap rubber that stands between ice and your fittings.

• Pool antifreeze

  Pool-rated glycol for the lines air couldn't clear.

• Winter closing kit

  Season-length winter chemicals in one label-dosed box.

• Air pillow

  Gives ice somewhere to push besides your pool walls.

How Pasco compares locally

Pasco closes in the earliest quarter of Washington's calendar. Neighbors run close: Kennewick (4 mi away) models its deadline at October 11 (about a week later vs Pasco's October 4), while Yakima (72 mi) shows October 6. The spring mirror of this page is the Pasco opening guide, and the season overview draws both windows on a single bar.

Every number on this page traces to one instrument cluster: Pasco Tri Cities Airport, 1.3 miles northeast of Pasco's center at an elevation near 407 feet. NOAA computed its 1991–2020 normals from roughly three decades of daily readings — long enough that one strange spring in Franklin County barely moves the dates.

Field notes for Pasco owners

Salt cells overwinter indoors

Remove the cell at closing, inspect and clean per the manufacturer, and store it inside with the unions capped. A dummy cell or spacer keeps the plumbing sealed. Cells left in outdoor plumbing through freezes are a common — and completely avoidable — spring casualty.

Cold water is the whole point

A pool closed at 55°F barely changes all winter: algae are dormant, chemicals hold, and spring opens with a light dusting instead of a bloom. A pool closed at 72°F runs its own quiet ecosystem under the cover for a month. The date matters less than the water temperature it represents.

Gas heaters get the manual, not a guess

Every heater brand sequences its winterizing differently — drain plugs, blower considerations, gas supply, control settings. The generic advice (drain fully, close the valve) is right but incomplete; ten minutes with your model's manual protects the most expensive component you'll winterize.