Pool closing · Washington
When to Close Your Pool in Kent, WA: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
Circle October 1 on the Kent calendar. Closing earlier traps warm, algae-friendly water under the cover; closing later gambles the plumbing against the first freeze, which the 1991–2020 normals place near November 10. The window opens September 21 — the live widget below shows how this year is actually tracking against it.
Kent closing dates at a glance
| Closing window | September 21 – October 1 |
|---|---|
| Close by (deadline) | October 1 |
| First freeze, 50% probability | November 10 |
| Open by (recommended) | May 21 |
| Opening window | May 14 – June 4 |
| 61°F crossing (7-day mean) | June 4 |
| Swim-season length (80°F+ days) | 0 days |
| NOAA normals station | Kent · 2.4 mi · 30 ft |
Kent banks only about 0 days of 80°F-plus afternoons — early opening weeks are the cheapest season extension available.
The same model in water terms: Kent's estimated pool temperature runs about 51°F in mid-April, 62°F in mid-June, 68°F in mid-August, and 56°F in mid-October, peaking near 69°F. Those four checkpoints — not any calendar holiday — are what the windows above are protecting.
The 12-step Kent winterizing checklist
Sequenced against Kent's September 21–October 1 window: chemistry while the pump still runs, blowouts before the equipment drains, cover last. Labels dictate every dose.
-
Balance the water a few days ahead
Start midweek for a weekend close: bring alkalinity and pH into their label ranges and let the water settle. What you seal under the cover is what the pool soaks in until spring.
-
Deep-clean the pool
Make the last cleaning the best one of the year: full skim, full brush, careful vacuum. Debris left behind steeps all winter and greets you as April's water problem.
-
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.
-
Apply winter chemicals per label
Dose the winter kit while the pump still runs — every product exactly per its label for your volume — so the chemistry is fully mixed before the system goes quiet.
-
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.
-
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.
-
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.
-
Add pool antifreeze where blowouts fall short
If any line can't be verified dry, add pool-grade antifreeze per its label. Use only pool antifreeze — automotive products don't belong in pool plumbing.
-
Drain the equipment
Nothing on the pad should hold water overnight: pull the drain plugs from pump, filter, heater, and feeder, stash them all in the pump basket, and carry the portable pieces indoors.
-
Set the air pillow and cover
Center an inflated air pillow, then fit the cover and secure it with water bags, cable, or straps as designed. The pillow gives ice a place to push besides your walls.
-
Remove and store ladders and rails
Pull ladders, rails, and the diving-board hardware; rinse, dry, and store them out of the weather. Anchor sockets get a dab of protectant so spring bolts turn freely.
-
Store chemicals properly
Seal opened containers, keep oxidizers and acids separated, and store everything cool, dry, and locked away from kids and pets — exactly as each label describes.
What to buy before the rush
A small stack of supplies turns the checklist above into a single-weekend job. Buy before Kent's September rush and the whole list ships at leisure instead of sprinting.
-
Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
-
Pool antifreeze
Backup for unverifiable lines; label rate per foot of pipe.
-
Winter closing kit
Season-length winter chemicals in one label-dosed box.
-
Air pillow
Gives ice somewhere to push besides your pool walls.
-
Winter cover
The one purchase every other closing step depends on.
-
Cover pump
Solid covers collect rain all winter; this is the drainage plan.
How Kent compares locally
Two nearby data points to triangulate with: Auburn, 6 miles from Kent, models its close at October 1 (the same day); Renton, 6 miles out, at October 1. Kent's own window ends October 1. For the other half of the calendar see when to open in Kent, or scan the full year on the season page.
Every number on this page traces to one instrument cluster: Kent, 2.4 miles northwest of Kent's center at an elevation near 30 feet. NOAA computed its 1991–2020 normals from roughly three decades of daily readings — long enough that one strange spring in King County barely moves the dates.
Field notes for Kent 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.
The mesh-cover spring surprise, prevented in fall
Mesh-covered pools green up early because late-winter sun plus nutrient-carrying meltwater reaches the water. The fall counter-moves: close late and cold, dose the winter kit exactly per label, and plan an early-spring peek under the cover rather than a Memorial Day reveal.
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.
Hard-winter homework
Where winter is long — Kent banks only about 0 warm-swim days — the closing carries months of load. Bury the effort where it counts: verified-dry lines, fully drained equipment, a skimmer guard, and a cover secured for real wind. A short season forgives a late opening; it never forgives a cracked pump.
Kent pool closing FAQ
What temperature should water be to close a pool?
Cold enough that biology has clocked out — below 65°F and falling, ideally low 60s. The widget above tracks Kent's actual water; the normals say the durable cool-down arrives near September 21, and anything inside the window to October 1 closes clean.
Can you close a pool too early?
Early closing is the mistake the whole model is built to prevent from the other direction. A cover installed over 70°F water is a terrarium: sanitizer decays, algae compound, nobody looks for months. Kent's water isn't reliably out of that zone until about September 21 — the calendar's first cold weekend doesn't change that.
Do I need antifreeze in pool lines?
Blown-out, plugged lines don't need it; doubtful lines do. Use only antifreeze labeled for pools, at the label's rate per foot of pipe — never automotive antifreeze. In Kent the freeze clock starts around November 10, so settle this during closing, not during the first cold snap.
How far should I drain my pool for winter?
As far as your cover manufacturer specifies and no farther — typically a few inches below the skimmer mouth for solid covers, near normal level for many mesh systems with skimmer plugs. Never drain fully: an empty shell can shift or crack under groundwater pressure.
What happens if you don't winterize a pool?
The repair list writes itself in order of cost: heater heat exchanger, pump housing, filter tank, then every fitting the ice reached — discovered one leak at a time in spring. Around Kent the exposure begins near November 10, and each skipped checklist step above is one more candidate for that list.
When is the last safe date to close in Kent?
Our model's practical deadline is October 1 — set by the cool-down plus ten days (the freeze normal, November 10, leaves room to spare). Push much past it and you're winterizing in freeze-warning weather, rushing the blowout, and hoping the cover goes on before the first hard night. Inside the September 21–October 1 window, none of that drama applies.
Email me when Kent hits the closing window
Data: NOAA 1991–2020 climate normals via Kent (2.4 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.