How to Close a Swimming Pool for Winter | Pool Winterizing Checklist

Utah winters can be gorgeous, and rough on pools. Closing your pool the right way protects it from freeze expansion, keeps the water clearer through the off-season, and makes spring opening faster and cheaper. In this guide, you will learn exactly how to close a swimming pool for winter in Utah’s climate, from water balance to blowing out lines to installing a tight, wind-ready cover.

Planning a new pool or a remodel for next season? Book a design consult.

At-a-Glance Pool Closing Checklist

Test and balance water to winter targets
Brush walls, vacuum floor, empty baskets
Shock to raise free chlorine to about 10 to 12 ppm
Remove ladders, rails, cleaners, toys, and store dry
Lower water level 4 to 6 inches below lowest return
Drain equipment, backwash or clean filters, store drain plugs in pump basket
Blow out lines, add pool-grade antifreeze where needed, plug tight
Empty chemical feeders
Install winter cover securely and re-check after first storm

What “Winterizing a Pool” Really Means

Winterizing a pool means preparing the water, equipment, and plumbing so freezing temperatures and long idle months do not damage anything or create a swamp by spring. You will balance water chemistry to reduce corrosion and scaling, clean thoroughly so organics do not rot under the cover, drain equipment, and remove water from lines so it cannot freeze. You will also seal the system and cover the pool to keep out debris and sunlight, then check the cover during the winter.

Why it matters in Utah: temperatures routinely dip below freezing, elevation swings from St. George to Park City change when and how fast water cools, and fall leaves can clog skimmers overnight. Proper closing reduces freeze expansion risk, limits algae when daylight is short, protects pumps, filters, and heaters, and makes that first warm day in April a quick open, not a week-long cleanup.

When to start in Utah: after daytime highs are consistently below 65 degrees Fahrenheit and most leaves have dropped in your area. Along the Wasatch Front, that typically falls in mid to late October, with higher elevations closing earlier and St. George often stretching later.

Supplies You’ll Need

Reliable test kit or test strips for pH, total alkalinity, calcium hardness, and free chlorine
pH increaser or reducer, alkalinity increaser, calcium hardness increaser, sequestering agent to hit winter targets and prevent stains
Chlorine shock or non-chlorine shock for a final sanitizing boost
Skimmer plugs, return line plugs, Gizmos or skimmer guards to protect skimmer throats from ice pressure
Air pillow for above-ground pools to reduce ice stress and help shed water
Solid or mesh winter cover with cable and winch or anchor hardware sized correctly for your pool
Air compressor or shop vac to blow out lines from skimmer to returns and main drain
Pool-grade antifreeze for exposed or hard-to-clear runs after blowing out
Safety goggles and chemical-safe gloves for handling chemicals and feeders

The Step-by-Step Pool Closing Checklist

1. Balance Your Water

Targets for a winter close:

pH: 7.2 to 7.6
Total Alkalinity: about 100 ppm
Calcium Hardness: generally 100 to 400 ppm

Why it matters: balanced water reduces corrosion of metal components, limits scale on plaster and tile, and helps sanitizer work longer through cold months. Utah’s hard water can leave calcium behind if the balance is off, so take the time to dial it in.

Pro tip: if you have staining or hard water deposits, add a metal sequestering agent before the final circulation cycle. It ties up metals so they do not plate onto surfaces while the pool sits cold.

Winter Chemical Targets

Parameter	Target Range	Why It Matters
pH	7.2 to 7.6	Limits corrosion and scaling
Total Alkalinity	~100 ppm	Stabilizes pH through winter
Calcium Hardness	100 to 400 ppm	Reduces etching and scale formation
Free Chlorine	1.5 to 3.5 ppm	Ongoing sanitation under the cover
Final Shock Dose	10 to 12 ppm	Oxidizes organics and knocks back algae growth

2. Give It One Last Deep Clean

Skim the surface, brush walls and steps, and vacuum the floor methodically. Empty skimmer and pump baskets. The goal is to remove anything that would decay under the cover and stain your finish.

3. Shock the Pool

Raise free chlorine to about 10 to 12 ppm. Circulate the system long enough for full mixing, then let chlorine drift back toward the normal range, roughly 1.5 to 3.5 ppm, before you cover. This final oxidation step makes spring cleanup much easier.

4. Remove, Clean, and Store Gear

Take out ladders, handrails, diving boards, slides, robotic cleaners, toys, and leaf canisters. Rinse with fresh water, let everything dry fully, then store in a clean, dry spot. Label small hardware in a zipper bag so nothing goes missing.

5. Lower the Water Level

Use your filter pump on waste or a submersible pump. Aim for about 4 to 6 inches below the lowest return line. This helps keep water out of the return fittings and skimmers through freeze-thaw cycles.

Above-ground pools: ensure water sits below the skimmer, or remove the skimmer and install a winterizing plate. Add an air pillow to relieve ice pressure and help snowmelt move toward the edges.

6. Drain and Protect Equipment

Remove drain plugs on the pump, filter tank, heater, and chlorinator so water can escape completely. For sand or DE filters, backwash before you shut down. For cartridges, clean thoroughly and let them dry.

Store all drain plugs in the pump basket so you know exactly where they are in spring. Disconnect power to equipment during the off-season. Dry, empty equipment handles Utah freezes much better.

7. Blow Out the Lines, Then Plug

This is the heartbeat of closing an inground pool for winter in a freeze climate. Using an air compressor or a strong shop vac, blow air through each line until you see a strong bubble at the return or the main drain. Plug each return while air is flowing to lock out water. For the main drain, blow until it bubbles, then close the valve while it still bubbles to create an air lock.

In colder zones or for exposed runs, add pool-grade antifreeze into the lines after blowing them out, then install winter plugs. Do not use automotive antifreeze.

8. Empty Chemical Feeders

Safely drain chlorine or acid feeders and cap them. Wear goggles and chemical-safe gloves for this step. Leaving product inside can damage seals and feeders over winter.

9. Install the Winter Cover

For above-ground pools, center and inflate an air pillow before the cover goes on. It reduces ice pressure and sheds water and leaves toward the ring.

For inground pools, install a solid or mesh cover snugly with proper tension on straps or the cable system. Utah winds can gust hard, so aim for a flat, tight cover with minimal slack. After the first light snow or wind event, re-check tension, adjust, and clear puddles so water does not stretch the fabric.

Special Notes for Different Pool Types

Vinyl liner pools: avoid lowering the water too far, since liner shrinkage can occur in cold, dry air. Use a liner-safe brush and a gentle vacuum head to avoid scuffs at closing.

Plaster or pebble finishes: watch calcium hardness to reduce etching or scale. If you see white crust on tile as the water drops, clean it now so it does not cement in place over winter.

Salt systems: turn the salt chlorine generator off and follow all standard pool closing steps. Balance first, then shock, then proceed with water level, equipment, and lines.

Safety, Care, and Winter Watch-Ins

Keep children and pets away from covered pools at all times.
After storms, pump off standing water on solid covers and clear leaves so ice does not form around debris.
Do a mid-winter spot check for slack straps, wind lift along the edges, torn grommets, or sagging. Tight and tidy means less mess in April.
In canyon areas and higher elevations, consider a second check after significant freeze-thaw cycles.

Common Mistakes to Skip

Closing while the water is still warm and algae is active
Forgetting to remove equipment drain plugs
Neglecting to blow out lines in freeze country
Skipping water balance, which turns into scale, stains, or both by spring
Leaving toys or ladders under the cover
Relying on a loose cover that flaps in the wind

When To Call a Pro

Bring in a professional when you have complex plumbing runs, attached spas, sheer descents or laminar jets, or automation settings you are not comfortable changing. If you have a history of freeze damage, find visible air leaks while plugging lines, or want a smooth open as early as March or April, a pro close is worth it.

Thinking about changes at spring opening? Explore custom pool remodel and design options with Stevenson Brothers Custom Pools. Our in-house team can also add custom hot tubs and spas, sculpted waterfalls, and signature water features to elevate your backyard.

FAQs

Do I need pool antifreeze if I blow out the lines well?
Often no for lines that are fully blown clear and properly plugged. Use pool-grade antifreeze for exposed plumbing, long runs that trap water, or pools in deep-freeze microclimates.

Solid or mesh cover?
Solid blocks sunlight and debris best and keeps water cleaner, while mesh handles heavy snow load better and requires less pumping. Many Utah owners choose mesh in snowier areas and solid in lower-snow, high-leaf zones.

Can I winterize a salt pool the same way?
Yes. Turn the generator off, hit the same balance targets, shock, then proceed with equipment and plumbing steps.

What day-night temperature pattern signals it is time to close in Utah?
When daytime highs stay under about 65 degrees for a week and nights are near or below freezing, algae slows and the water cools enough to close. Also watch local leaf drop; when most trees are bare, it is a good window.

How low should I set my water if I have raised walls or laminar jets?
Lower at least 4 to 6 inches below the lowest return line. If laminars, bubblers, or raised wall returns sit higher, make sure water is below those fittings before you blow out and plug the lines.

Do I need to run the pump after I shock for closing?
Yes. Run the pump to circulate the shock evenly. After levels drift toward normal, shut the system down and proceed with equipment and plumbing steps.

Ready To Plan Your Dream Backyard For Spring?

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