Can I Leave Pool Filter Outside for Winter? Storage Guide

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Quick Answer

No, you should not leave most pool filters outside during winter in freezing climates. Trapped water in the filter housing, manifolds, and internal components will freeze, expand, and crack plastic or fiberglass parts. Sand, cartridge, and DE filters all require proper winterization including complete draining and ideally indoor storage.

Why Pool Filters Can't Handle Freezing Temperatures

Pool filters contain numerous areas where water can become trapped, even after you think you've drained everything. The main risks include:

• Filter housing cracks: Plastic and fiberglass housings are particularly vulnerable to freeze damage
• Internal manifold damage: DE filters have delicate internal components that crack easily when frozen
• Valve and plumbing connections: Multiport valves, drain plugs, and pressure gauges contain water that expands when frozen
• O-ring deterioration: Freezing temperatures can cause rubber seals to become brittle and fail

Proper Winter Storage for Different Filter Types

Sand Filters

Sand filters are the most robust but still require winterization:

1. Set multiport valve to "Winterize" position if available, or "Filter" if not
2. Remove the drain plug from the bottom of the tank
3. Remove pressure gauge and any additional drain plugs
4. Backwash thoroughly before draining to remove debris
5. Allow 24-48 hours for complete drainage
6. Store drain plugs and pressure gauge indoors to prevent loss

Sand filters can sometimes survive outdoors if completely drained, but indoor storage is safer and extends equipment life.

Cartridge Filters

Cartridge filters require more careful winterization:

1. Remove all filter cartridges and clean thoroughly
2. Drain the tank completely through drain plugs
3. Remove lid o-ring and store indoors
4. Store cartridges in a dry, indoor location
5. Leave tank lid slightly ajar to allow airflow and prevent moisture buildup

Store cleaned cartridges in a garage or basement where they won't freeze but have good ventilation.

DE (Diatomaceous Earth) Filters

DE filters are the most vulnerable and absolutely must be stored properly:

1. Backwash to remove all DE powder
2. Disassemble the filter and remove all grids or fingers
3. Clean grids thoroughly and inspect for damage
4. Drain tank completely and remove all drain plugs
5. Store grids flat in a dry indoor location
6. Remove and store manifold assembly indoors if possible

Never leave DE filters outside in freezing weather - the complex internal components are extremely expensive to replace.

Climate Considerations

Your local climate determines storage requirements:

• Warm climates (no freezing): Filters can remain outside with proper chemical balance maintenance
• Occasional freezing: Drain completely but outdoor storage may be acceptable
• Extended freezing periods: Indoor storage is essential
• Extreme cold climates: All equipment should be stored in heated spaces when possible

Alternative Winter Protection Methods

If you cannot store your filter indoors, consider these options:

• Insulated covers: Custom-fit insulated covers can provide some protection
• Heat tape: Electrical heat tape can prevent freezing but increases utility costs
• Antifreeze: Only use pool-safe propylene glycol antifreeze, never automotive antifreeze
• Partial disassembly: Remove the most vulnerable components for indoor storage

Pre-Season Inspection

Before reinstalling your filter in spring:

1. Inspect all housing for hairline cracks
2. Test all o-rings and gaskets for flexibility
3. Check pressure gauge accuracy
4. Verify all drain plugs and fittings
5. Replace any questionable components before filling

Common Winter Storage Mistakes

Avoid these costly errors:

• Assuming the tank is empty: Always remove drain plugs and allow extended drainage time
• Forgetting about the multiport valve: These contain water in multiple chambers
• Leaving pressure gauges attached: These freeze and break easily
• Storing dirty cartridges: Clean thoroughly to prevent permanent staining and bacterial growth
• Using automotive antifreeze: This is toxic and will contaminate your pool water

Cost of Freeze Damage

Proper winterization pays for itself by preventing expensive repairs:

• Sand filter tank replacement: $300-800
• DE filter manifold assembly: $150-400
• Cartridge filter housing: $200-600
• Multiport valve replacement: $100-300

The 30 minutes spent properly winterizing your filter can save hundreds in spring repairs.