Pool closing · Utah
When to Close Your Pool in Sandy, UT: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
In Sandy, the closing window runs from September 30 to October 10. Let the water cool out of the algae-growth range before covering — close too warm and you lift the cover onto a green surprise in spring — but finish ahead of the first freeze, which normals place around October 22. The live estimate below shows where Sandy's water sits today.
Sandy closing dates at a glance
| Closing window | September 30 – October 10 |
|---|---|
| Close by (deadline) | October 10 |
| First freeze, 50% probability | October 22 |
| Open by (recommended) | May 7 |
| Opening window | April 30 – May 21 |
| 61°F crossing (7-day mean) | May 21 |
| Swim-season length (80°F+ days) | 95 days |
| NOAA normals station | Cottonwood Weir · 4.8 mi · 4986 ft |
Sandy's 95-day warm season leaves comfortable margins on both ends — the windows above aim you at the cheap-chemistry versions of each transition.
At roughly 4986 ft, Cottonwood Weir runs cooler than lowland forecasts for the same region — trust these local numbers over metro-wide weather graphics.
Put dates aside and follow the water: the Sandy curve says roughly 49°F by mid-April, 67°F by mid-June, 79°F in mid-August, then back down through 57°F in mid-October. The summer ceiling sits near 80°F, and every window above is just a line drawn on this curve.
The 12-step Sandy 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.
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Balance the water a few days ahead
Three or four days before closing, adjust alkalinity and pH into label ranges. Balanced water is gentler on the liner, plaster, and equipment through the long covered months ahead.
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Deep-clean the pool
Skim, brush walls and steps, and vacuum carefully. Any leaves or algae you seal under the cover become spring's chemistry problem, so closing day cleanliness pays twice.
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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.
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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.
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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.
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Blow out the lines and plug returns
The blowout is the whole ballgame: drive air through each line until it runs dry, seat the plug against the airflow, move to the next. A dry line cannot burst, full stop.
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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.
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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.
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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.
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Set the air pillow and cover
Inflate the pillow to about two-thirds, center it, then bring the cover over and secure it per its design. Under ice, that soft dome is the difference between inward compression and outward wall pressure.
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Shut down the heater carefully
Follow the manufacturer's winterizing sequence for your heater — drain it fully and, for gas units, close the supply valve. Heat exchangers are the most expensive freeze casualty on the pad.
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Note this year's dates
Jot down when Sandy's water actually cooled and when you closed. A two-line note beats memory next September 30 — your own yard runs a few days off any model, including ours.
What to buy before the rush
The September crowd empties shelves in a predictable order. This is the short list worth owning before Sandy's window opens — nothing exotic, just the stuff everyone needs the same weekend.
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Winter closing kit
Closing chemistry in one box, dosed by pool volume.
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Air pillow
Centers under the cover so ice pushes inward, not outward.
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Winter cover
Measure with overlap; the winter workhorse over everything else.
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Cover pump
Keeps rain and melt off a solid cover all season.
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Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
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Pool antifreeze
For lines you can't verify dry — pool-grade only, per label.
How Sandy compares locally
Statewide context: across the 12 Utah cities we model, Sandy's October 10 deadline sits in the later half. Nearby, South Jordan (7 mi) closes around October 10 and West Jordan (8 mi) around October 10 — treat gaps under a week as microclimate noise, not strategy. Spring planning restarts at the opening guide; the Sandy pool season page keeps the whole year in one view.
Local means local: Sandy's dates come from Cottonwood Weir, the nearest station with complete daily temperature normals — 4.8 miles northeast, about 4986 feet up. Between that station and a Salt Lake County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Sandy owners
The warm spell after you closed
A 78°F week in October doesn't mean reopening. Water under an opaque cover warms far less than air suggests, and a closed, balanced pool tolerates a warm stretch fine. Check the cover pump has somewhere to send rain, enjoy the weather, and leave the plumbing sealed.
What comes indoors
Cartridges, the cover pump when idle, chemical containers, and anything with a small motor overwinter better in the garage. Cold cycling is hard on plastics and seals; shelf space is cheaper than replacements. Label a single bin now and spring assembly becomes a scavenger hunt with a map.
Match the drainage plan to the cover
Solid covers shed nothing — they need a cover pump staged before the first storm and checked after each one. Mesh covers drain themselves but pass silt that settles all winter. Either way, the plan is decided in October, not improvised in January when the cover is an ice sheet.
Closing for a real winter
A Sandy closing has to hold for months of freeze-thaw, not a few frosty mornings. Spend the effort where winters bite: prove every line dry, drain every vessel on the pad, guard the skimmer, and tension the cover for wind that will actually come. The reward is a spring opening that's a rinse, not a rebuild.
Closing at 4986 feet
High-elevation autumns lie: Sandy afternoons can feel like swim weather the same week a clear night dips below 32°F. The defense is preparation — blowout gear staged early, the October 22 freeze normal taken literally, and any dry cold front in October treated as the starting gun rather than a curiosity.
Sandy 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 Sandy's actual water; the normals say the durable cool-down arrives near September 30, and anything inside the window to October 10 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. Sandy's water isn't reliably out of that zone until about September 30 — the calendar's first cold weekend doesn't change that.
Do I need antifreeze in pool lines?
Treat antifreeze as a backup, not a substitute: the real protection is air in dry lines. Where a full blowout isn't possible, pool-grade antifreeze per label is cheap insurance against a cracked pipe — worth it anywhere freezes are routine, and Sandy sees them from about October 22.
How far should I drain my pool for winter?
Less than most people think. Below the skimmer opening is the classic solid-cover target; mesh covers often specify higher water. The cover's own manual wins every argument, and "drain it completely" is never the answer — empty shells pop out of wet ground.
What happens if you don't winterize a pool?
In a freeze climate, physics wins: water expands about 9% when it freezes, cracking pump housings, filter tanks, heat exchangers, and pipes. With Sandy's first 32°F night arriving near October 22 in the normals, an unwinterized pad is a spring repair bill waiting to be discovered.
When is the last safe date to close in Sandy?
Our model's practical deadline is October 10 — set by the cool-down plus ten days (the freeze normal, October 22, 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 30–October 10 window, none of that drama applies.
Email me when Sandy hits the closing window
Data: NOAA 1991–2020 climate normals via Cottonwood Weir (4.8 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.