Closing depends on climate. In freeze states, it means clearing water out of every pipe and housing that can crack, then sealing the pool under a cover until spring. In the Sun Belt, most pools never close; they shift to a lighter cool-season routine with a plan for the occasional hard freeze.
Steps 1 through 5 are the full winterization. Florida, Texas, Arizona and California owners can jump to the cool-season section near the end.
When to close in a freeze state
Wait until water temperature holds below about 65°F. Algae grows slowly in cold water, so a pool closed in cool weather stays cleaner under the cover. Close during an early-September heat spell and the chlorine runs out while the water is still warm enough to grow algae.
- A winter cover with no tears, plus every strap, spring or water bag it needs.
- Rubber expansion plugs sized for your return fittings, and a skimmer plug or ice compensator.
- A shop vac that blows, or a dedicated pool line blower.
- Non-toxic propylene glycol pool antifreeze if you plan to use it.
- A drop-count test kit and enough liquid chlorine to shock.
Step 1: Balance, clean and shock
Start about a week before closing day so the chemistry has time to settle.
- 1Set pH to 7.2 to 7.6, alkalinity to 80 to 120 ppm, and calcium to the range for your surface. Calcium at the upper end protects plaster over a long winter. Ranges are in pool chemical levels explained.
- 2Brush and vacuum thoroughly. Debris left on the floor feeds algae all winter.
- 3Shock to about 40% of the stabilizer reading, roughly 16 ppm with CYA at 40, and run the pump continuously until free chlorine drops 1 ppm or less overnight.
- 4Let chlorine fall below about 5 ppm before adding a winter algaecide, because high chlorine breaks algaecide down. Choose a non-metal product; copper-based algaecides can stain plaster.
- 5Clean the filter. Backwash sand or DE, or hose and soak a cartridge in filter cleaner.
For shock doses, one gallon of 10% liquid chlorine raises 10,000 gallons by about 10 ppm. A 20,000-gallon pool going from 2 to 16 ppm needs about 2.8 gallons. The pool chemical calculator does the math for other strengths and products.
Step 2: Lower the water level
Lower the water to keep freezing water out of the skimmer and off the tile line. The right level depends on the cover and how you protect the plumbing.
| Setup | Typical water level |
|---|---|
| Mesh safety cover | About 12 to 18 inches below the skimmer, or below the lowest return |
| Solid safety cover or solid winter cover | About 3 to 6 inches below the skimmer; the cover needs water support |
| Skimmer sealed with a plug and lines blown out | Some pros leave the level near normal; follow the cover maker's guidance |
| Above-ground pool | Just below the skimmer and return; never drain an above-ground pool |
Step 3: Blow out and plug the lines
Water left in buried pipes freezes, expands and cracks fittings you cannot reach without cutting into the deck. In a hard-freeze climate, this step prevents the most expensive damage.
- 1Turn the pump off at the breaker.
- 2At the equipment pad, push air through each line toward the pool with a shop vac on blow or a dedicated blower.
- 3When steady bubbles come out of a return, plug it with a rubber expansion plug while air is still flowing.
- 4Blow out the skimmer line, then seal the skimmer with a skimmer plug or ice compensator.
- 5Blow out the main drain line until it bubbles, then close its valve to trap an air lock in the line.
- 6Optionally add propylene glycol pool antifreeze to the lines as insurance. Never use automotive antifreeze.
Step 4: Drain and protect the equipment
- Remove the drain plugs from the pump, filter, heater and chlorinator. Store them in the pump basket so they are there in spring.
- Set a multiport valve to Winterize or Closed, or between positions if your manual says so.
- Remove the salt cell, pressure gauge and any chemical feeder; rinse them and store them indoors.
- Store the pump motor indoors if you can. Otherwise cover it loosely so it can breathe without trapping condensation.
- Turn off the breakers for the pump, heater, lights and automation.
Step 5: Cover it and check monthly
Install the cover to the manufacturer's instructions with every strap or spring tensioned. Above-ground pools get an air pillow under the cover to absorb ice expansion.
Once a month, pump standing water off solid covers, clear heavy snow from above-ground covers, and check the water level. A level that drops more than an inch or two between checks points to a leak.
Sun Belt pools: a cool-season routine
In Florida, South Texas, Arizona and coastal California, a closed pool causes more problems than it solves. Still water under a cover in a mild winter usually turns green. Keep the pool open and scale the routine back.
| Task | Cool-season approach |
|---|---|
| Pump run time | Shorter, but still enough to turn over the full volume once a day |
| Chlorine | Demand drops in cool water; keep free chlorine in range for your stabilizer |
| Salt generator | Many cells stop producing below a set water temperature, often in the 50s °F; supplement with liquid chlorine |
| Cleaning | Weekly or every other week, depending on debris and screen enclosure |
| Heater | Inspect before you need it; clear vents and check for insect nests |
Freeze protection is the main risk. Automation with a freeze sensor starts the pump when air temperature drops near freezing, usually around 36 to 38°F. Test that setting before the first cold snap. Without automation, run the pump all night on freeze nights; moving water rarely freezes in pipes.
When to call a pro
Most expensive winterizing mistakes happen on a first closing, usually from water left in a line or a heater. Pay for a pro closing or a freeze-damage check in these cases.
- You do not have a blower, or you are not sure every line was cleared.
- The pool has a heater, an in-floor cleaning system or long plumbing runs.
- You find cracked fittings, a split pump housing or a leaking heater after a freeze.
- A Sun Belt pool's freeze protection did not run during a cold snap.
What weekly pool service costs near you
Frequently asked questions
Do I need to close my pool in Florida or Texas?
Usually not. In most of Florida and South Texas, pools stay open year-round on a lighter routine. Make sure the pump runs on freeze nights. In North Texas and other colder areas, a full winterization is worth considering.
How far should I lower my pool water for winter?
It depends on the cover. Mesh covers usually call for about 12 to 18 inches below the skimmer, while solid covers need the water closer to the skimmer for support. Follow the cover maker's guidance and never drain an in-ground pool.
Can I close my pool without blowing out the lines?
In freeze states it is risky. Water left in buried pipes can freeze and crack them, and the repair often means cutting into the deck. In mild climates where the pump keeps running, circulation protects the lines.
Should I shock my pool before closing it?
Yes, about a week before closing. Then let chlorine drop below about 5 ppm before adding winter algaecide, since high chlorine breaks algaecide down.
Should I run my pool pump during a freeze?
Yes, if the pool is open. Moving water protects pipes and equipment. If the power goes out during a freeze, drain the pump, filter and heater by removing their drain plugs.
Poolside guides are written for homeowners and checked against current pool chemistry and equipment guidance. Doses assume a standard drop test kit and are given per 10,000 gallons.
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