How to Winterize a Pool Filter
Published
Quick answer
Winterize 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.
Safety
A pool filter is a pressurized vessel. Never loosen a clamp, lock ring, valve, gauge, drain or lid while pressure is present. Shut the pump off, open the manual air-relief valve as the manual directs, stand clear, and verify zero pressure before service. Use qualified help if the tank, closure, valve or winterization procedure is uncertain.
Identify the filter type and exact model first
Cartridge, sand and DE filters do not use the same media or service procedure. Record the model number and obtain the current manual before removing drain plugs, opening a valve or deciding whether internal cleaning is part of the closing job.
Depressurize before draining or opening anything
Pentair's filter safety guidance requires shutting the pump off and relieving pressure through the manual air-relief valve before service. Do not treat winterization as an exception to the pressure-vessel safety procedure.
Use the filter's designed drain point
Many pool filters include a dedicated drain for service or winterization. Pentair's Clean & Clear Plus, for example, describes an easy-access drain intended to simplify winterization. Sand-filter drain arrangements can differ and may involve water and media considerations, so use the exact filter manual.
| Filter type | What must be drained or serviced | Why the manual matters |
|---|---|---|
| Cartridge | Tank water, drain assembly and cartridge/service condition as specified | Closure, drain size, cartridge handling and storage/service instructions vary by model |
| Sand | Tank water and valve/drain configuration as specified | Some designs combine water/media drain functions; do not remove sand simply because the pool is closing unless the manual calls for it |
| DE or modular media | Tank water, valve/drain configuration and media/grid/module service according to the model | DE and modular systems differ in backwash, media replacement and internal assembly procedures |
Do not leave water trapped in attached filter plumbing
Draining the tank does not automatically drain the pump, heater, salt cell, multiport plumbing, return line or other connected components. The entire freeze-prone circulation path must be addressed by the closing method.
Keep drain plugs and small parts organized
Label removed drain plugs, caps and model-specific pieces. Photograph the drain locations, valve positions and pressure gauge before leaving the system for winter so spring reassembly is not guesswork.
Inspect the tank, closure and gauge before spring restart
If freezing, age or service damaged the tank, clamp/lock ring, pressure gauge, air-relief valve, O-rings or plumbing, do not pressurize the filter until the problem is corrected with compatible parts and the manufacturer procedure.
Restart with the air-relief procedure in spring
Pentair's current support guidance says the air-relief valve should remain open during restart until water comes out, allowing trapped air to escape. Follow the exact startup sequence for the filter rather than simply turning the pump on against a closed winterized system.
What you may need
- Model-specific replacement filter drain plug only if damaged/missing
- Filter tank O-ring/body seal if diagnosis shows replacement is needed
- Compatible pressure gauge if faulty
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.
Pool filter drain plug
Model-specific drain plug, cap, or gasket used on compatible pool filters. Match the exact filter make, model, drain location, and manufacturer part specification before ordering.
Places to check
Pool filter tank O-ring or body seal
Model-specific seal used at a pool filter tank, lid, or body joint. Match the exact filter make, model, seal location, and manufacturer part specification before ordering.
Places to check
Pool filter pressure gauge
Replacement gauge for reading filter pressure at the tank.
Places to check
Related guides
- 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 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.
- Why Is My Pool Filter Leaking?Shut the pump off before diagnosing a filter leak and relieve all filter pressure exactly as the filter manual directs. Pentair says that if water leaks from the filter's joined body sections after restart, the pump should be shut off immediately. Once the system is fully depressurized and the gauge is at zero, identify the leak location. O-rings, gauges, valves, drain fittings, air-relief components, plumbing joints, and tank/clamp problems require different parts and different safety decisions.
- 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.