Most pool owners treat closing day as a single Saturday of work. That is exactly why so many of them open in April to a green swamp, a cracked filter tank, or a heater that will not fire. A proper winterize pool closing checklist does not start on closing day — it starts fourteen days earlier, and the sequence matters more than the effort.
The two weeks before you pull the cover over your pool are the window where chemistry, filtration, and equipment prep either set you up for a clean spring opening or quietly guarantee an expensive one. This guide walks the full countdown day by day, with the exact numbers, the brand-specific filter procedures, the pressure readings, and the repair costs that come with getting it wrong.
- Why the Countdown Starts Two Weeks Out
- Tools, Chemicals, and Prerequisites
- Why the Chemical Order Cannot Be Shuffled
- The 10-Step Autumn Countdown
- Filter Deep Clean by Brand and Model
- Normal vs Abnormal Pressure Readings
- Salt System Codes and Cold-Water Shutdown
- Costly Mistakes and What They Actually Cost
- Safety Rules You Must Never Break
- Warranty Traps Hiding in Your Closing Routine
- Your Off-Season Maintenance Schedule
- Frequently Asked Questions
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Why the Countdown Starts Two Weeks Out
The single biggest closing mistake is closing early. Algae and bacteria multiply rapidly in warm water, and a pool sealed under a cover while the water is still warm burns through its winter sanitizer in weeks instead of months. You end up with a warm, stagnant, covered pool — the ideal incubator for the green, smelly, stained mess you will find in spring.
The trigger is temperature, not the calendar. Wait until outdoor air and pool water temperatures drop consistently below 65°F. Some closing guidance pushes that even lower, to 60°F and below. Below that threshold, algae metabolism slows enough that your winter chemicals can hold the line for six to eight months of stagnation.
That is why the prep window opens two weeks before your target close date. You need the water still warm enough to circulate chemicals properly and the filter still running, but close enough to the cold that the work you do now still counts when the cover goes on.
Close only after air and water temperatures sit consistently below 65°F. Closing warmer wastes your winter sanitizer and all but guarantees a green opening — and restoring a neglected algae-swamp pool runs into hundreds of dollars in rescue chemicals, with professional remediation easily exceeding $100 per week.
Tools, Chemicals, and Prerequisites
Gather everything before Day 14. Chasing a missing socket or an out-of-stock algaecide mid-countdown is what breaks the sequence, and a broken sequence is what wastes the chemicals you already added.
Testing and cleaning: A reliable liquid test kit or fresh test strips. A telescoping pole, pool brush, skimming net, vacuum head, and vacuum hose.
Filter service tools: A socket wrench with a 7/8-inch socket for Pentair and Hayward clamp bands, a 3/4-inch socket or wrench for Hayward multiport and select grid assemblies, a torque wrench, and a rubber mallet.
Reassembly supplies: Teflon thread tape, a silicone- or Teflon-based pool lubricant such as Jack’s Formula 327 or Magic Lube, and a soft-bristle cleaning brush.
Chemicals: Carbonate and bicarbonate balancers (pH Up/Down, Alkalinity Up, Calcium Hardness Increaser), a sequestering metal and stain inhibitor such as Metal Free or Stain Away, granular chlorine shock (cal-hypo or sodium dichlor), a non-chlorine oxidizing shock such as Fresh ‘N Clear, a phosphate-remover and enzyme blend such as Pool Magic + PHOSfree, and a non-copper winter algaecide.
Winterizing accessories: Tapered rubber winterizing plugs in sizes #8 through #12 depending on your return sizes, threaded 1.5-inch plugs with O-rings, a Skimguard or Gizzmo skimmer winterizer, a pool cover pump, and a high-volume low-pressure air blower such as the Cyclone 3 HP Pool Blower.
One prerequisite before any of it: bring the water level to standard operating height, midway up the skimmer mouth. Everything in the countdown depends on full, unrestricted circulation, and a low water level starves the skimmer.
Skimming, brushing, and vacuuming across fourteen days is exactly when a flexing, seizing pole fails you. Our 490 Promise covers this pole for life — residential users get unlimited replacements, so the tool you close with this fall is the tool you open with next spring.
Why the Chemical Order Cannot Be Shuffled
Pool chemicals are not a shopping list you dump in over a weekend. Added in the wrong order, they deactivate each other, cloud the water, or permanently stain your surfaces. Three rules govern the whole countdown.
Water balance comes first. Total Alkalinity has to be correct before you touch pH, because TA is the buffer that holds pH stable. With TA too low, pH swings erratically and nothing you do downstream holds. Bring pH to the lower end, 7.2 to 7.4, before shocking — low pH maximizes the sanitizing potency of hypochlorous acid, while high pH renders chlorine shock largely ineffective.
Sequester metals before you shock. If copper, iron, or manganese are dissolved in your water, high chlorine levels and pH spikes will instantly oxidize them and drop them out of solution. That means permanent staining on plaster or vinyl. Lock the metals up first, then shock.
Shock before algaecide, never together. Free chlorine above 5.0 ppm oxidizes and destroys the polymer chains in winter algaecide and degrades stain-prevention chemicals. You superchlorinate, circulate, and then wait several days for free chlorine to fall back to 1.0 to 3.0 ppm before the algaecide and enzyme treatments go in.
Adding chlorine shock and winter algaecide on the same day is one of the most common closing errors. The chlorine destroys the algaecide outright, and you will have to buy and apply a second round once free chlorine drops back into range.
The 10-Step Autumn Countdown
Here is the full sequence, mapped against the days remaining before you cover the pool.
Pull out the winter safety cover or solid tarp and spread it out. Inspect every panel for rips, tears, and dry rot, and patch damage immediately with a cover patch kit. Count your brass deck anchors and locate the tamping tool, brass springs, and hex keys. Order your pre-sized winter chemical kit now, based on your pool’s total gallonage — this is the one step with a lead time you cannot compress.
Skim all leaves, twigs, and floating debris with a deep mesh leaf rake. Brush every wall, step, cove, corner, and shady crevice from the shallow end toward the deep end to lift sediment and disturb early algae spores. Vacuum the floor completely. If your system allows it, vacuum directly to Waste so heavy dirt bypasses the filter media entirely.
Test the water and balance Total Alkalinity first, to 80–120 ppm. Aim for 100–120 ppm if you use trichlor, dichlor, or bromine, and 80–100 ppm for liquid chlorine or cal-hypo. Once TA is stable, adjust pH to 7.4–7.6, or 7.2–7.4 if calcium is high. Bring Calcium Hardness to 200–400 ppm and Cyanuric Acid to 30–50 ppm. Balanced water is what prevents scaling and corrosive damage across six to eight months of stagnation.
Add a metal chelating agent such as Metal Free or Stain Away to lock up dissolved iron, copper, and manganese. Dose 1 liter of MetalFree or 1 quart of stain and scale remover per 20,000 gallons, poured evenly around the pool perimeter with the pump running on high speed. Let the pump run continuously for 8 to 10 hours to fully disperse it before any algaecide or oxidizer goes in.
Superchlorinate to destroy bacteria, organic contaminants, and microscopic algae spores. Broadcast granular cal-hypo or sodium dichlor across the deep end to raise free chlorine to 10.0 ppm. Brush the walls and floor immediately afterward so nothing settles and bleaches the liner. Run the pump on high speed for 8 to 12 hours to circulate the shock fully.
Add a phosphate remover and enzyme treatment such as Pool Magic + PHOSfree directly into the skimmer with the pump running. Use 14 fluid ounces per 10,000 gallons — a standard 1-liter bottle treats 25,000 gallons. Give it 24 to 48 hours of circulation to precipitate phosphates and break down organic residues before you lower the water level.
Tear down and chemically clean your filter elements, whether that means D.E. grids, cartridge elements, or a sand bed. Closing with dirty media traps organic waste and bacteria in the tank all winter, which causes permanent media damage, filter calcification, and a severe algae problem at spring opening. Brand-by-brand procedures are in the next section.
Set your pump timer or automation to run 24 hours a day for several days straight. Add a maintenance dose of water clarifier such as Ultra Bright Advanced to coagulate ultra-fine suspended particles. This maximizes water purity, blends every chemical you have added, and drives the last fine debris into your freshly cleaned filter.
With the pump running, broadcast non-chlorine shock such as Fresh ‘N Clear around the perimeter at 1 to 2 pounds per 10,000 gallons. It burns out organic contaminants without raising chlorine, so it will not attack the winter algaecide you are about to add. Wait 30 minutes before moving on to the final steps.
Skim any windblown debris one last time. Kill the breaker to the pump and heater. Drain the water below the skimmer mouth — 4 to 6 inches below for a solid cover, 9 to 12 inches below for a safety cover. Pour in your chelated, non-staining winter algaecide or Polyquat 60. Activate and drop in your slow-release winter chemical floater. Blow out all lines, seat your winter plugs and Gizzmos, and anchor the cover drum-tight.
Always shock at dusk or after dark. Ultraviolet light burns off unstabilized chlorine at roughly 1 ppm per hour, so a mid-afternoon shock can lose most of its punch before it ever finishes oxidizing the contaminants you are targeting.
Broadcasting granular cal-hypo straight onto a vinyl, painted, or fiberglass surface will bleach and damage it. Pour 1 to 2 pounds at a time into a 5-gallon bucket of water, stir until fully dissolved, then pour the solution around the pool edge — and keep any undissolved granules at the bottom of the bucket out of the pool.
Autumn debris loads are the heaviest of the year, and a shallow net turns one pass into six. This deep leaf rake clears volume fast, clips to any standard pole, and is backed by the 490 Promise — if it fails, we replace it.
Filter Deep Clean by Brand and Model
Step 7 is where most closings get rushed, and it is the step with the most brand-specific detail. Torque specs, soak ratios, and clamp procedures differ meaningfully between manufacturers, and guessing at them is how tanks fail.
- Pro-Grid D.E. (DE2420, DE3620, DE4820, DE6020, DE7220): Pump off, open the manual air relief valve, set the multiport or slide valve to Closed, and pull the lower 1.5-inch drain plug. Backwash first — on a 6-position Vari-Flo valve (SP0710XR50 / SP0715XR50) push down and rotate to BACKWASH, run 2 minutes or until the water out the waste line runs clean, stop, set to RINSE and run 20 seconds, stop, then return the valve to FILTER. On a 2-position slide valve (SP0410X502S), pull the handle straight up into BACKWASH, twist to lock, run 2 minutes.
- Pro-Grid disassembly and soak: Loosen the clamp nut and bolt with a 3/4-inch socket, lift the lid off (never by the air relief valve), and lift the grid nest out by the manifold handles. Hose the grids down, then soak in 1 cup of TSP per 5 gallons of hot water for at least 3 hours — overnight is better. Rinse fully, then soak 3 to 4 hours in 1 part muriatic acid to 10 parts water for scale. Never acid-soak before removing oils, or the reaction bakes them permanently into the fabric.
- Pro-Grid reassembly: Inspect the DEX2422Z2 tank seal, clean the lower tank rim, and lubricate the standpipe O-ring with Jack’s Lube No. 327. Torque the clamp nut to exactly 150 inch-lbs with a torque wrench. Never strike the clamp with a metal tool. Recharge with D.E. slurry through the skimmer: DE2420 takes 3.0 lbs, DE3620 4.5 lbs, DE4820 6.0 lbs, DE6020 7.5 lbs, DE7220 9.0 lbs. Clean startup pressure typically runs 8 to 15 PSI.
- SwimClear cartridge (C2030, C3030, C4030, C5030, C7030): Same 3/4-inch clamp removal and 150 inch-lb reassembly torque. Hose each pleat at a 45-degree angle top to bottom, soak overnight in 1 cup TSP per 5 gallons of hot water, then 1 part acid to 20 parts water for scale. Do not lubricate the SwimClear DEX2422Z2 seal. Overhead clearance to lift elements: C2030 15″, C3030 16″, C4030 18″, C5030 22″, C7030 28″. Clean at 7 to 10 PSI above baseline.
- S-Series sand (S180T, S210T, S244T, S310T2): Sand charges are 150 lbs, 200 lbs, 300 lbs, and 500 lbs respectively of #20 silica (0.45–0.55 mm). Deep clean by backwashing 2 to 3 minutes, rinsing 1 minute, then pouring sand filter revitalizer into the pump basket with the valve on BACKWASH. Run the pump 10 to 15 seconds to drive it into the bed, shut off, soak 12 hours, then backwash 3 to 5 minutes and rinse 1 minute. For winter, set the valve handle directly between two detente positions — the Winterize position — which lifts the diverter about 1/4 inch so trapped water can expand without cracking the valve body. Leave the bottom drain cap off all winter.
- FNS Plus D.E. (FNSP24, FNSP36, FNSP48, FNSP60): Kill power at the breaker, open the high-flow air relief valve a quarter turn counter-clockwise until the gauge reads 0 psi, and pull the bottom drain plug. Loosen the clamp barrel nut with a 7/8-inch socket until the spring fully decompresses, slide the clamp ring off, lift the lid straight up, and remove the grid nest by its manifold handles.
- FNS Plus cleaning: Hose the grids, then soak in a commercial D.E. degreaser for several hours to strip oils. For scale, soak at least 4 hours in 6 parts water to 1 part muriatic acid and rinse thoroughly. On reassembly, clean the tank flange rims and bottom plate lip, lubricate the tank O-ring with Lifegard Silicone only — never a petroleum-based lube — and seat the grid marked SMALL GRID on the matching bottom spreader position first.
- FNS Plus clamp and recharge: Tighten the clamp barrel nut with the 7/8-inch socket until the spring coils are fully compressed and physically touching, tapping the band lightly with a rubber mallet around the perimeter to seat it. D.E. charges: FNSP24 2.4 lbs, FNSP36 3.6 lbs, FNSP48 4.8 lbs, FNSP60 6.0 lbs. Clean when pressure reads 10 psi above the clean start. Vertical clearance to lift the grid nest: FNSP24 48″, FNSP36 62″, FNSP48 74″, FNSP60 86″.
- Clean & Clear Plus cartridge (CCP240, CCP320, CCP420, CCP520): Shut off pump and breaker, open the air relief until the gauge reads 0 psi, drain the tank. Remove the 7/8-inch barrel nut, spring, and washers, lift the lid, then pull the top manifold, compression spring, and spring adapter before extracting each element. Hose each cartridge at a 45-degree angle through every pleat, soak at least 1 hour — overnight preferred — in 1 cup TSP per 5 gallons, then 1 part acid to 20 parts water for 10 minutes or until bubbling stops. Clean at approximately 10 PSI above the clean baseline — note that the 8 to 10 PSI figure belongs to Pentair’s single-element Clean & Clear and Posi-Clear RP models, not the Plus series. Clearance: CCP240 56″, CCP320 62″, CCP420 68″, CCP520 74″.
- DEV Series D.E. (DEV48, DEV60): Pump and breaker off, open the air release valve on the tank top, pull the base drain plug. Remove the clamp ring and lid, then lift the grid assembly out by the molded manifold handles. Rinse the grids clean.
- DEV soaking: Degrease in 1 cup of TSP or dishwasher detergent per 5 gallons of water for at least 3 hours, then rinse. Decalcify for at least 3 hours in a 10:1 water-to-muriatic-acid mixture and flush thoroughly with fresh water.
- DEV reassembly: Rinse the empty tank, clean the sealing surfaces, replace the drain plug, and lubricate the tank O-ring with silicone — do not stretch it. Lower the grid nest in, fit the clamp ring, and tighten while tapping lightly with a rubber mallet around the perimeter until the gap between the clamp plates does not exceed 1/16-inch. Recharge with slurry through the skimmer: DEV48 takes 5.0 lbs of D.E., DEV60 takes 6.0 lbs. Clean the grids at 10 to 12 PSI above the clean baseline.
- Pro CL / CV cartridge (CL340, CL460, CL580) and CS single-element: Shut off pump and breaker, open the air release, drain the tank. Remove the clamp ring and lid and pull the cartridges. Hose each pleat top to bottom, degrease with TSP first, then de-scale in a 1:20 muriatic-acid-to-water solution. Wipe the upper and lower container flange rims completely free of dust before reassembly. Lubricate the tank O-ring lightly with silicone and tap the clamp with a rubber mallet while tightening for an airtight seal. Clean at 8 to 10 PSI above baseline, or 10 to 12 PSI on CV/CL models. Note that CS single-element cartridges carry a hard 105°F (40.6°C) maximum water temperature limit to protect the internal core.
- Laminated cartridge filters: Pump off and power disconnected, open the air relief valve to release system pressure, pull the base drain plug. Open the tank, remove the cartridges, and hose them clean top to bottom. Soak overnight in commercial filter cleaner or TSP to break down oils, and soak in 1:20 muriatic acid if calcium is present. Rinse, lubricate the O-rings with silicone, reassemble, and restart.
- Active winterizing (circulation continues): Below 51°F (11°C) the chlorinator will not produce chlorine at all — that cold-water cutoff is automatic. If a freeze controller is running your pump through the winter and you keep the chlorinator online, turn chlorine production down to 10–20%, or output will push past the recommended 1.0 to 3.0 ppm and start corroding pool metals.
- Passive winterizing (hard shutdown): Switch the appliance off and drain the condenser on the back of any heat pump by unscrewing the water inlet and outlet connectors. For a full closing, tighten those two connectors back by exactly one turn so foreign bodies cannot enter the condenser. If you are winterizing the heater only while the pump keeps running, do not tighten the connectors — fit the two provided caps directly onto the condenser water ports instead.
Lifting algae spores off the walls before you shock, and brushing again right after you broadcast, is the difference between shock that works and shock that settles. Magnetic ring-lock ends mean the head cannot fall off mid-stroke, and the 490 Promise covers replacement for life.
Normal vs Abnormal Pressure Readings
Your filter’s pressure gauge is the single most useful diagnostic on the pad, and closing season is when you should be reading it carefully. Most residential systems operate normally between 5–15 PSI or 10–20 PSI, with 10 PSI a common clean starting benchmark. What matters is not the absolute number but the rise above your own clean baseline.
Manufacturers generally say to clean at 8 to 10 PSI above the clean start, or 10 to 12 PSI on Jandy sand and cartridge models. For pump efficiency, particularly on variable-speed systems, cleaning at a 25% rise is better practice.
| Clean baseline | Manufacturer clean point | 25% efficiency clean point |
|---|---|---|
| 10 PSI | 18–20 PSI | 12–13 PSI |
| 15 PSI | 23–25 PSI | 18–19 PSI |
| 20 PSI | 28–30 PSI | 25 PSI |
Two readings demand immediate attention. A spike above 30 to 40 PSI on start-up means you should shut the pump off at once and check for a closed valve, a winterizing plug you forgot to remove, or severely blocked media. And a pressure reading that drops below your clean baseline is not good news — it means flow is restricted upstream of the filter, typically a clogged skimmer basket, a packed pump strainer basket, or a blocked impeller.
Never operate or pressure-test a pool circulation system above 50 PSI. Pressurized filter tanks and plumbing fittings can fail catastrophically, and the failure mode is a lid or clamp launched with lethal force.
One more efficiency note that surprises people: backwashing or cleaning more often than the pressure calls for actually reduces fine-particle filtration. A slightly loaded filter traps smaller particles than a spotless one. Clean on the gauge, not on the calendar.
Salt System Codes and Cold-Water Shutdown
If you run a salt chlorine generator, the cell has its own opinions about cold water, and it will act on them without asking you. Knowing the thresholds keeps you from misreading a normal winter shutdown as a failure.
| System | Indicator | Meaning and threshold |
|---|---|---|
| Pentair IntelliChlor (standard) | Low salt (red LED) | Salt below 2,800 ppm — reduced efficiency (some versions flag it at 3,300 ppm) |
| Pentair IntelliChlor Plus / LT | ADD SALT warning | Salt has dropped below 3,000 ppm |
| Pentair IntelliChlor and Plus / LT | SYS OFF LOW SALT (red LED) | Generation halted below 2,600 ppm to protect the cell plates |
| Pentair iChlor | Low salt (red LED) / not enough salt | Red LED between 2,600 and 3,000 ppm; reduced output between 2,000 and 2,600 ppm; full shutoff below 2,000 ppm |
| Pentair IntelliChlor Plus / LT | LOW TEMP warning | Water has fallen below 60°F (15°C). On standard IntelliChlor units, 60°F instead caps output at 20% |
| Pentair IntelliChlor and iChlor (all lines) | SYS OFF LOW TEMP / COLD | Full shutdown at 52°F ± 3°F (11°C) to extend cell life |
| Hayward AquaTrol | Low Salt LED | Illuminates below 2,500 ppm |
| Hayward AquaRite | Check Salt LED | Flashing at 2,400–2,700 ppm (low efficiency); steady at 2,300 ppm or below, and chlorine production is suspended |
| Hayward AquaTrol and AquaRite | Generating LED flashing | Generation stopped because water dropped below 50°F |
| Hayward AquaRite Pro / Pro Logic | Check System message | pH control auto-disabled after the AQL-CHEM4-ACID dispensing pump ran past its timeout |
| Hayward OmniLogic / OmniPL | Alarm icon and alarm list | Shows named faults such as pH Timeout, CHLOR Low Salt, or CS&D pH High level. Note these controllers need the HL-CHEM Sense & Dispense unit — the older AQL-CHEM is not compatible |
| Hayward OmniLogic / OmniPL | Shut Down screen | Reports when it is safe to remove power before winterizing |
| Zodiac power control | Flashing green / alternating blue-green-red / steady red | Standby or timer delay / firmware update in progress, do not disconnect / active fault |
| Jandy TruClear XL | HELLO, STANDBY, CHLORINATING % | Start-up, paired pump off or at 0 RPM, and normal operation respectively |
A flashing generating light in November is your cell protecting itself, not breaking. Note also that Hayward’s Salt & Swim and AquaRite are separate product lines with different controls — do not apply one line’s thresholds to the other.
Costly Mistakes and What They Actually Cost
Every item on the countdown exists because skipping it has a price. Here are the failures that show up most often, and what they cost to fix.
Skipping the line blowout. Water expands 9% to 10% when it freezes. Trapped water in pipes, pumps, filters, and heaters will crack plastic, copper, and cast iron. A replacement heater heat exchanger runs over $2,000 plus labor, which is often enough to push owners into replacing the whole heater. A cracked inground skimmer means cutting through the concrete deck and digging — at least $1,000 to $2,000-plus in professional labor. A cracked pressurized filter tank cannot be repaired at all; epoxy patches on filter tanks are structurally unsound and will not hold, so you are buying a replacement tank half or full assembly at 50% to 80% of the cost of a new filter.
Draining the pool for winter. This one is close to a total loss. Draining removes the outward water weight that counters groundwater pressure. Concrete and fiberglass shells can physically float out of the ground when the water table is high. Vinyl liners dry out, shrink, pucker, and rip permanently when refilled. Above-ground walls can fall inward and collapse in a strong breeze. Re-leveling a floated pool or replacing collapsed walls runs into thousands.
Pouring shock or tablets into the skimmer. With the pump off, concentrated chemical dissolves in still skimmer water and drives the pH to strongly acidic. When the pump restarts, that slug of acidic, superchlorinated water is pulled straight through the pump, heater, and filter. It corrodes copper heat exchangers, degrades plastic housings, and destroys O-rings — and it voids equipment warranties.
Running a cover pump on a torn cover. If the cover has an unpatched hole, the submersible pump pulls water from underneath it and drains your pool. The falling water level removes the support the heavy cover needs, and the whole thing — snow, ice, and rotting leaf soup — collapses into the pool. Replacement solid covers cost hundreds, and the cleanup takes weeks of labor and heavy chemical spend. That is why cover inspection is Day 14, not closing day.
Vacuuming flocculant into the filter. Floc binds fine debris into heavy clumps by design. Send that into a cartridge or D.E. filter and it gums the elements beyond recovery — they get replaced, not cleaned. Sand filters need a deep manual wash.
The equipment-specific damage from skipping the Day 6 filter clean is worth spelling out. In sand filters, oils and dead algae push deeper into the bed and, over months of stagnation, clump into sticky mud-balls; with hard water, calcium fuses the bed into solid sandstone and water channels straight through it unfiltered. In D.E. filters, damp dirty powder dries and cakes onto the monofilament fabric, permanently blinding the pores and causing immediate pressure spikes next spring. In cartridge filters, oils, algae, and scale embed into wet polyester fibers all winter, separating the weave so fine dirt bypasses the filter, weakening the support bands, and collapsing the pleats under pump pressure.
Safety Rules You Must Never Break
Closing a pool involves pressurized vessels, strong acids, and concentrated oxidizers. These rules are not cautionary — each one exists because the failure mode is severe.
Purging a pool filtration system with high-pressure compressed air can make pressurized plastic tanks, lids, and pipes explode with deadly force. Always use a low-pressure, high-volume blower — under 5 PSI — such as a Cyclone blower. You only need 3.5 PSI to clear a pipe submerged under 8 feet of water.
Never turn the multiport valve handle while the pump is running. Doing so can dislodge or tear the rubber spider gasket inside the valve, which then leaks water permanently out of the wrong ports — including to waste — during normal filtration.
Never stand over or within five feet of the filter tank during start-up. Air trapped in the tank acts like a compressed spring. If the clamp band or lid is loose, misaligned, or damaged, the lid can separate violently and launch several feet with fatal force. Open the manual air relief valve first, stand clear, and do not close the relief valve until a steady stream of water is coming out.
Never adjust, loosen, or tighten a clamp band while the system is pressurized. That is the exact action that triggers a tank explosion.
Never mix pool chemicals. Combining chlorine types — cal-hypo shock with trichlor tablets, for example — creates a violent reaction that generates lethal chlorine gas and can explode.
Never handle dry D.E. powder or muriatic acid without protection. Wear safety goggles, chemical-resistant gloves, and a dust mask. Diatomaceous earth is sharp microscopic silica classified as a carcinogen when inhaled, and muriatic acid causes severe burns to eyes, skin, and airways. When diluting acid, always pour the acid slowly into the water — never water into acid.
Warranty Traps Hiding in Your Closing Routine
Several of the shortcuts above do more than cost you a repair — they cost you the coverage that would have paid for it.
Freeze damage is universally excluded. Every major pool equipment manufacturer states that allowing water to freeze inside the pump, filter tank, heater, or chlorinator vessel voids the warranty. Freeze damage is classified as user negligence, which means the full cost of that $2,000 heat exchanger lands on you.
Feeding chemicals upstream voids coverage instantly. Pouring algaecide, balancers, or shock directly into the skimmer or a chemical cycler can damage internal O-rings and melt gaskets, and manufacturers treat it as abuse. Feeder systems must be plumbed downstream of all filters and heaters.
Running the pump dry voids the motor warranty. Operating without water in the strainer pot overheats and ruins the mechanical shaft seal, leading to leaks and motor failure. This is an easy mistake to make during closing when water levels are dropping.
Copper algaecide in a mineral system voids the stain warranty. If you run a mineral purifier such as Nature2 or Jandy TruGuard, adding a copper-based winter algaecide completely voids the manufacturer’s stain-free warranty. Use a chelated non-copper product or Polyquat 60.
Third-party media voids cycler warranties. Bulk chemical tablets or unapproved mineral cartridges in FROG cyclers void coverage. Those cyclers — Prevail, Prevail 120, Perform-Max — also need 4 to 8 PSI of back-pressure to run the erosion chamber correctly, and lower back-pressure results in under-chlorination.
Your Off-Season Maintenance Schedule
The cover going on is not the end of the job. A closed pool still needs eyes on it, and the checks are quick.
- ☐ Every visit: Clear leaves, pine needles, and trash off the winter cover.
- ☐ Every visit: Keep skimmer baskets, pump strainer baskets, and cleaner bags free of debris so flow is never blocked.
- ☐ At least monthly: Inspect the cover for tears, confirm safety cover straps are taut, and verify the water level has not dropped from an undetected leak.
- ☐ At least monthly (above-ground): Check that the air expansion pillow is still properly inflated so the walls cannot buckle.
- ☐ Every 6 to 8 weeks (mild winters): Test and balance pH, Total Alkalinity, Calcium Hardness, and Free Chlorine.
- ☐ Every other week (if temps sit between 60°F and 70°F): Increase water testing frequency.
- ☐ Whenever a freeze is forecast: If the pool is still running, run the pump 24/7 on high speed to keep water moving through the plumbing.
- ☐ Twice a year: Chemical wash for sand filters.
- ☐ Every 3 to 6 months: Deep clean cartridge filters.
- ☐ Every 6 months (4× a year in warm climates): Manual teardown, grid wash, and chemical degrease for D.E. filters; rebuild D.E. filters annually.
Calculate your volume before you buy. Rectangular: average length × average width × average depth × 7.5. Circular: diameter × diameter × average depth × 5.9. Oval: long diameter × short diameter × average depth × 5.9. Standard kits treat up to 7,500 gallons, Deluxe up to 15,000, and Premium/Ultimate up to 35,000. An undersized kit dilutes the algaecide and sanitizer and leaves the water unprotected all winter.
Frequently Asked Questions
Do I need to add chemicals to my pool during the winter?
Yes. Algae growth slows dramatically in cold water but does not stop, and you still need to maintain a free chlorine level of 1.0 to 4.0 ppm through the off-season. For covered pools, a winterizing dose of algaecide plus natural enzymes such as Pool Perfect or Pool Magic destroys organic matter, prevents winter scum lines, and makes for a far cleaner spring opening.
What water temperature should I wait for before closing the pool?
Wait until both air and pool water temperatures sit consistently below 65°F, with some guidance recommending 60°F and lower. Closing while the water is still warm lets algae and bacteria multiply under the cover, burns through your winter sanitizer early, and leaves you opening to a green, stained pool that costs hundreds in rescue chemicals to recover.
Why does freezing water damage pool equipment so badly?
Water expands 9% to 10% as it turns from liquid to solid ice, and the force behind that expansion is immense. It easily cracks cast iron and polymer heater headers, ruptures pump volutes, splits plastic pipes, separates multiport valve flanges, and cracks pressurized filter tanks. Filter tank cracks in particular cannot be patched — epoxy repairs are structurally unsound and will not hold pressure.
Can I use a shop vac or air compressor to blow out my pool lines?
A high-volume, low-pressure blower such as a Cyclone 3 HP is ideal. If you use an air compressor, keep the pressure below 5 PSI — you only need 3.5 PSI to clear a pipe sitting under 8 feet of water. Never use high-pressure compressed air, because it can make plastic filter tanks and plumbing fittings explode with hazardous force.
How much should I inflate an above-ground pool air pillow?
Only inflate air pillows to 50% to 60% of their total capacity. The pillow, also called an ice compensator, sits in the center of the pool under the cover and absorbs the pressure of expanding surface ice and heavy snow so the metal walls do not buckle. Underinflating leaves the give the ice needs to press against, whereas a fully inflated pillow simply pops.
How often should I clean or backwash my filter before closing?
Clean on the pressure gauge, not the calendar. Backwash or clean when pressure climbs 8 to 10 PSI above your clean baseline, or 10 to 12 PSI on Jandy sand and cartridge models, or at a 25% rise for best pump efficiency. Cleaning more often than that actually reduces fine-particle filtration, because a lightly loaded filter traps smaller particles than a spotless one.
What should I do to my pool after a heavy autumn storm?
Skim, brush, and vacuum immediately, because storm debris and organic contaminants will exhaust your sanitizer fast. Check skimmer and pump baskets frequently, since they clog quickly and can cause the pump to lose prime. Balance pH to 7.4–7.6 and Total Alkalinity to 80–120 ppm first — acidic rainwater suppresses both — then follow with a cal-hypo or dichlor shock to 10.0 ppm.
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