Pool Closing Mistakes That Create Expensive Spring Problems
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Quick answer
The most expensive closing mistakes happen when owners treat winterization as a cover installation instead of protection for an entire water-and-equipment system. The high-risk errors are closing with active algae or debris, guessing at chemistry, leaving freeze-prone water in equipment or plumbing, using mismatched plugs or fittings, choosing a water level without considering the pool and cover, and assuming the pool needs no attention until spring.
Safety
If winterizing plumbing or equipment requires compressed air, electrical work, gas/heater procedures, or steps you cannot verify from the manuals, stop and use a qualified professional.
Mistake 1: Closing a green or dirty pool
A cover does not fix algae, leaves, or sediment. Remove debris and regain control of the water before closing so the off-season starts with the smallest practical contamination load.
Mistake 2: Adding a closing kit without testing
Bundled products can be convenient, but the pool's actual chemistry should determine what is needed. More chemical is not automatically more protection, and products can be incompatible with particular sanitizers, surfaces, or each other.
Mistake 3: Guessing at the water level
The correct closing level depends on pool construction, skimmer protection, cover design, groundwater conditions, and climate. A partial warm-climate closure can even require maintaining normal water level so circulation continues. Use the method specified for the pool.
Mistake 4: Leaving water trapped where it can freeze
Freeze damage occurs when expanding water is confined in plumbing or equipment. Proper winterization addresses pumps, filters, heaters, sanitizers, exposed pipes, valves, and other water-containing components according to their manuals and the plumbing design.
Mistake 5: Losing track of plugs and settings
A bag of unlabeled plugs in the garage makes spring startup harder than it needs to be. Label removed parts and photograph the equipment pad before and after closing.
Mistake 6: Using a damaged or poorly fitted cover
Inspect the cover, anchors, straps, water bags, or other attachment system before winter. A cover that cannot manage the weather expected at the site is not protection.
Mistake 7: Ignoring the pool until spring
Inspect the cover and surrounding drainage after storms. Remove accumulated water from a solid cover when its instructions require it, and address damaged anchors or excessive loads promptly.
Mistake 8: Waiting until the freeze has already arrived
Winterization is easier and safer before plumbing and equipment are frozen. Schedule professional work early enough that the pool can be closed deliberately rather than during an emergency cold front.
What you may need
- Winter pool cover
- Pool cover pump where appropriate
- Winterizing plugs
- Skimmer protection device
- Water test kit
Products mentioned in this guide
These are product categories referenced by the guide, not tested or ranked picks. Check the product description, your pool or equipment model, and the seller listing before buying.
Winter pool cover
Pool cover selected for the pool type, dimensions, anchoring method, weather exposure, and manufacturer installation requirements.
Places to check
Pool cover pump
Pump used to remove accumulated water from compatible solid pool covers. Follow the cover and pump instructions.
Places to check
Pool winterizing plugs
Model- and plumbing-size-specific plugs used as part of a proper winterization procedure. Match thread and fitting size before purchase.
Places to check
Skimmer winterizing plug or gizmo
Skimmer protection device selected to match the skimmer and the winterization procedure used for the pool.
Places to check
Comprehensive pool water test kit
A DPD/FAS-DPD style kit used to read chlorine, pH, alkalinity, stabilizer and hardness.
Places to check
Related guides
- When Should You Close Your Pool for Winter?There is no universal closing date. Pools exposed to sustained freezing conditions need a real winterization plan, while many warm-climate pools can remain open or use a partial winter routine. Pentair advises winterization where snow, sleet, or temperatures around or below 32°F are a consistent part of winter, and its Sun Belt guidance describes year-round or partial operation in warmer climates. Use local freeze risk and the equipment manuals, not the first cool weekend, to decide.
- How to Close an In-Ground Pool for WinterA winter closing is a system-protection job, not simply putting on a cover. Clean and balance the pool first, then follow the exact equipment and plumbing winterization procedure for the installation. In freeze climates, the most consequential work is getting water out of, or safely protected within, vulnerable equipment and lines. If you cannot verify that step, hire a pool professional.
- How to Winterize an Above-Ground PoolAbove-ground winterization protects both the water system and the pool structure. Clean and balance the pool, remove equipment and accessories that should be stored, follow the pump/filter/plumbing manuals, protect the skimmer and return fittings according to the pool's winterization method, and install a cover intended for that pool. Do not drain an above-ground pool simply because winter is coming unless the pool manufacturer specifically directs it.
- What Chemicals Do You Need to Close a Pool?There is no universal list of chemicals that every pool must receive at closing. Test the water first, correct meaningful balance or sanitation problems, and then use only winterization products that are compatible with the pool surface, sanitizer, cover, and equipment. Pentair's current winterization guidance tells owners to balance the water and shock before adding winterization chemicals, but the exact products and doses still come from the measured water conditions and each product label. A bundled closing kit is a convenience, not a substitute for testing.
- Should You Lower the Water When Closing a Pool?Sometimes, but not by one universal number. Pentair's full winterization guidance says lowering water can help with freeze and overflow protection, while its Sun Belt partial-closure guidance explicitly says not to lower the water because circulation continues through the skimmers. The correct level depends on whether the pool is fully winterized or kept circulating, the cover, skimmer-protection method, pool construction, groundwater conditions, and local professional guidance.
- How to Protect Pool Equipment From FreezingUse one of two deliberate strategies: properly winterize freeze-prone equipment and lines for a seasonal closure, or, for a brief cold event in a pool that remains open, maintain the circulation/freeze-protection strategy specified for the installed system. Pentair says freeze-protection automation or continuous circulation can help during short freezing periods, but connected freeze protection can depend on power, sensors, internet or weather services. Have a plan for a power outage, because circulation cannot protect plumbing when the pump cannot run.
- How to Winterize a Pool PumpA pool pump is winterized by preventing freeze-prone water from remaining trapped in the pump and connected plumbing. Shut the equipment down safely, follow the exact pump manual for drain plugs, pot/lid position, unions and storage, and winterize the suction/return lines as a separate plumbing task. Pentair's current winter guidance specifically references removing pump pot and volute drain plugs during severe winter conditions. Do not run a pump dry as a substitute for draining it.
- How to Winterize a Pool FilterWinterize the installed filter model, not a generic “filter.” Shut the pump off, relieve all vessel pressure through the manual air-relief procedure, and drain the filter using the model's specified drain points. Cartridge, sand and DE filters use different internal media and service procedures. Pentair's current filter safety guidance emphasizes pressure relief before service, and several Pentair filter families include dedicated drains specifically for service and winterization.
- Pool Closing Supplies Checklist: What You Actually NeedBuy supplies from the closing plan, not the other way around. Most owners need water-testing and cleaning supplies, an appropriate winter cover, and model/plumbing-specific items for the chosen winterization method. Freeze-climate closures may also require skimmer protection, line plugs and equipment drain parts. Above-ground cover systems may use an air pillow. Chemicals depend on measured water conditions and product compatibility. Do not buy a giant kit first and then invent reasons to use every item in it.
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General reference information for pool owners. It is not a substitute for your equipment manuals, product labels, or a qualified local pool professional. Read our editorial standards.