How to Winterize Pool Equipment: Prevent Costly Freeze Damage

Why Equipment Winterization Is Critical

Water Expansion Physics

Freezing point: Water freezes at 0°C (32°F).

Expansion rate: Water expands approximately 9% as it transitions from liquid to solid ice.

Pressure generation: Ice formation creates internal pressure exceeding 2,000 PSI. That’s far beyond what pool equipment housings can withstand.

Damage Costs

Pump replacement: €300-800 depending on horsepower, model.

Filter replacement:

• Sand filter tank: €400-800
• Cartridge filter housing: €300-600
• DE filter tank and grids: €600-1,200
  
  

Heater repair: €600-2,000 for heat exchanger replacement or complete unit.

Pipe replacement: Burst underground pipes require excavation, adding €500-2,000+ to repair costs beyond pipe material.

Prevention cost: €0 if equipment is properly drained. Winterization requires time (30-60 minutes) but no expense.

Step-by-Step Equipment Winterization

Step 1: Turn Off All Power

Circuit breaker: Shut off dedicated pool equipment breaker at electrical panel before touching any equipment.

Why critical: Prevents accidental pump startup while equipment drained (motor damage), eliminates electrocution risk when handling wet electrical components.

Automation systems: Set to “Service” or “Off” mode before power shutoff. Some systems retain settings when powered down; others reset.

Step 2: Close Valves

Purpose: Prevent pool water from draining through equipment as you open drain plugs.

Valves to close:

• Skimmer valve (isolates suction line)
• Main drain valve (if separate control)
• Return valves (prevents water flowing back from pool)
  
  

Exception: If equipment located below pool water level, valves MUST be closed or the pool will drain when equipment opens.

If no valves present: Lower pool water level below return jets and skimmer before draining equipment.

Step 3: Winterize Pool Pump

Drain plug locations: Most pumps have 2 drain plugs on the bottom of pump housing (volute). One on the inlet side, one on outlet side.

Procedure:

1. Remove pump strainer lid (large threaded lid on top of pump)
2. Remove strainer basket, empty debris, rinse clean
3. Remove both drain plugs from pump housing bottom
4. Water drains from pump body
5. Tilt pump gently side-to-side to drain remaining water from internal chambers
6. Leave drain plugs out all winter so you can allow any condensation to escape
7. Store plugs in strainer basket (won’t lose them)
8. Optional: If pump has unions on inlet/outlet, disconnect and tip entire pump to drain more thoroughly
   
   

Storage options:

Leave in place (most common): Drain completely, leave plugs out, cover with waterproof tarp or pump cover protecting from snow/rain.

Store indoors: Disconnect pump from plumbing via unions, carry to garage/basement. Ideal for severe winter climates, extends pump lifespan by eliminating weather exposure.

Lubrication: Apply a thin layer of pool lubricant (Teflon-based, silicone-based) to pump lid o-ring and union o-rings. Prevents cracking from cold, ensures proper seal at spring startup.

Step 4: Winterize Pool Filter

Sand Filters

Drain procedure:

1. Turn the multiport valve handle to “Winterize” position (if available) or position handle between two settings (e.g., between Backwash and Rinse). Lifting handle off detents allows air into the tank accelerating drainage.
2. Open air relief valve on top of filter tank (small knob or lever)
3. Remove drain plug from bottom of filter tank
4. Water drains from tank (10-30 minutes for large tanks)
5. Leave air relief valve and drain plug open all winter
6. Store drain plug in pump basket
   
   

Multiport valve: Set between positions prevents valve seal from sticking during winter. Some manufacturers specify a “Closed” or “Winterize” setting. You can always consult a manual.

Sand maintenance: Do NOT remove sand. Sand remains in the tank through winter. Backwash before winterizing to clean sand.

Cartridge Filters

Drain procedure:

1. Open air relief valve on top of tank
2. Remove drain plug from bottom of tank
3. Open tank (unscrew clamp band or twist-lock lid)
4. Remove cartridge(s)
5. Clean cartridges thoroughly: rinse with hose, soak in filter cleaner solution overnight, rinse again
6. Inspect for tears, damaged pleats, or crushed cores and replace if damaged
7. Allow cartridges to dry completely (2-3 days in ventilated area)
   
   

Storage options:

Option 1 – Store cartridges indoors: Protects from weather, maximizes lifespan. Store in a dry location (garage, shed).

Option 2 – Reinstall in tank: Place dried cartridges back in tank, close lid loosely (allows ventilation), leave drain plug and air relief open.

Lubrication: Apply pool lubricant to tank o-ring before closing tank or before storage.

DE (Diatomaceous Earth) Filters

Drain procedure:

1. Backwash filter to remove old DE coating from grids
2. Open tank (unscrew clamp band)
3. Open air relief valve on top
4. Remove drain plug from bottom
5. Remove filter grids: Lift grid assembly out of tank
6. Rinse grids thoroughly with hose, removing all DE residue
7. Inspect grids for tears in fabric and replace damaged grids
8. Allow grids to dry completely
   
   

Storage:

Grids: Store dried grids in a tank or indoors. If storing in the tank, leave the tank open or lid slightly ajar for ventilation.

Tank: Leave drain plug and air relief open all winter.

Do NOT add DE before storage: Tank and grids should be clean, dry, empty of DE.

Step 5: Winterize Pool Heater

Critical steps:

1. Turn off gas supply (gas heaters) – close valve on gas line to heater
2. Turn off electrical power – circuit breaker or disconnect switch
3. Allow heater to cool: If recently used, wait 15-20 minutes for heat exchanger to cool
4. Remove drain plug(s) from heat exchanger
   
   

Drain plug locations (varies by model):

Most heaters: 1-2 drain plugs on front inlet-outlet header (horizontal pipe at base of heater where water enters/exits).

Some models: Additional drain plug on rear return header (access by removing side cabinet panels).

Newer Raypak models: ProTek Shield module unscrews from front header, provides drainage point plus should be removed and stored indoors.

Procedure:

1. Remove drain plug(s)
2. Open pressure relief valve (if equipped) – accelerates drainage
3. Tilt heater toward drain side if possible (gets more water out)
4. Optional: Disconnect plumbing unions, tip heater to drain more thoroughly
5. Store drain plugs in pump basket
   
   

Vent protection: Place mesh screen over exhaust vents (top of heater). Prevents rodents from nesting inside heaters during winter. Use aluminum window screen or wire mesh, secure with zip ties or wire.

Cabinet panels: Some manufacturers recommend removing side panels for ventilation. Consult manual.

Step 6: Winterize Chlorinators and Salt Cells

Inline Chlorinators (Tablet Feeders)

Procedure:

1. Remove lid, remove all chlorine tablets (will dissolve into concentrated solution over winter)
2. Rinse canister thoroughly with hose
3. Remove drain plug from bottom (if equipped)
4. Store drain plug in pump basket
   
   

Storage: Can remain in place (drained) or store indoors.

Salt Chlorine Generators

Critical: Salt cells MUST be removed before freezing temperatures. Freezing water inside cell cracks electrode plates, housing (€300-800 replacement cost).

Procedure:

1. Turn off power to salt system
2. Unscrew unions connecting cell to plumbing (hand-tight or strap wrench)
3. Remove cell from plumbing
4. Inspect electrode plates for calcium scale buildup
5. Clean scale: Light scale (rinse with hose), moderate scale (gently scrape with plastic tool), heavy scale (soak in diluted muriatic acid 1:10 ratio for 15-30 minutes, rinse thoroughly)
6. Dry cell completely
7. Store indoors in climate-controlled location (garage, basement)
   
   

Dummy cell option: Install non-functional dummy cell (spacer matching dimensions) in place of real cell. Maintains plumbing loop sealed.

Control box: Can remain installed outdoors (designed for weather exposure) or stored indoors for maximum protection.

Blowing Out Plumbing Lines

Why Blow Out Lines

Equipment drainage removes water from pump, filter, heater but does not remove water from pipes.

Low spots: Pipes have low points where water pools even after equipment drains.

Underground pipes most vulnerable: Buried return and suction lines retain water. Freezing underground pipe bursts require excavation for repair (€1,000-3,000+ total cost).

Equipment Needed

Air compressor: Minimum 5-10 PSI capacity, up to 20 PSI maximum.

Shop vacuum (blower mode): Alternative to compressor for smaller pools, less effective than dedicated compressor.

Threaded adapters: Connect air hose to plumbing (pump drain plug port, skimmer, dedicated blow-out port if equipped).

Procedure

Return lines (from equipment to pool):

1. Connect air compressor to return line at equipment pad (pump drain plug port common connection point)
2. Start at low pressure 5-10 PSI
3. Gradually increase to 15-20 PSI
4. Watch return jets in pool – when steady stream of bubbles emerges, line clear
5. Continue air flow 2-3 minutes after bubbles visible
6. Immediately install winter plug in return jet (threaded rubber plug from inside pool) while air still flowing – maintains air lock preventing water from refilling line
   
   

Skimmer line:

1. Connect air to skimmer line (at pump or through skimmer opening)
2. Blow air until bubbles emerge from skimmer in pool
3. Immediately install gizzmo (skimmer guard) in skimmer – screws into basket cavity, absorbs ice expansion protecting skimmer from cracking
   
   

Main drain: Typically left open without plug. Air lock created by blowing prevents water from refilling during winter.

Safety: Never exceed 20 PSI – high pressure can blow out fittings, damage o-rings, crack PVC pipes.

Pool Antifreeze Addition

Type: Non-toxic propylene glycol pool antifreeze ONLY. Never automotive antifreeze (ethylene glycol – toxic, damages pool surfaces).

Quantity: 1 gallon per 10 linear feet of plumbing.

Application: Pour into skimmer after gizzmo installation, add to return lines if not confident lines fully blown out.

Function: Lowers freezing point to -20°C to -50°C depending on concentration, protecting pipes if any water remains.

Emergency: Power Outage During Winter

If Power Fails and Pool Not Winterized

Pumps running for freeze protection lose power. Pipes can freeze within hours if temperatures drop below 0°C.

Immediate action:

1. Turn off circuit breaker (prevents pump starting without water when power restored)
2. Remove all drain plugs: pump (2), filter (1), heater (1-2)
3. Open filter air relief valve
4. Open any closed valves in plumbing (allows water to drain from pipes)
5. Pour pool antifreeze into skimmer and return lines if available
   
   

After power restored:

1. Reinstall all drain plugs
2. Prime pump (fill strainer basket with water)
3. Turn on circuit breaker
4. Start pump, check for leaks and normal operation
   
   

Prevention: Backup generator for pool equipment in regions with frequent winter power outages. Battery backup for the automation system maintains freeze protection settings.

Portugal and Mild Climate Considerations

Minimal Winterization Needed

Coastal Portugal (Lisbon, Porto, Algarve): Water rarely freezes. Sustained temperatures below 0°C are extremely rare.

Interior/mountainous areas: Occasional cold snaps 0-4°C possible, brief surface ice but underground pipes protected by earth insulation.

Simplified Approach for Mild Climates

Option 1 – Reduced operation:

• Run pump 2-4 hours daily instead of 8-12 hours
• Reduce chemical dosing
• Monitor equipment weekly
• No drain plugs removal needed
  
  

Option 2 – Partial winterization:

• Drain pump and filter (remove plugs) as insurance against rare freeze
• Leave heater operational (no drainage) for occasional use
• Keep plumbing full (no line blowing)
• Equipment remains in place
  
  

Option 3 – Full operation:

• Normal pump runtime
• Normal chemical maintenance
• Use pool year-round (Portugal’s mild climate permits October-May swimming with heating)
  
  

Natural pool advantage: Natural swimming pools with regeneration zones designed by Oásis Biosistema operate year-round in Portugal’s climate with minimal equipment requirements compared to conventional pools, maintaining biological filtration through winter with reduced pump runtime and no chemical additions.

Storage and Organization Tips

Drain Plug Storage

Store in pump basket: Standard practice – all drain plugs from pump, filter, heater go in pump strainer basket. Can’t lose them, easy to find in spring.

Label if needed: If multiple filters or complex systems, label plugs (masking tape, marker) indicating origin.

Small Parts Organization

Pressure gauge (sand filter): Remove from top of filter tank, store indoors (freezing damages gauge mechanism).

Sight glass (multiport valve): Remove if equipped, store indoors (glass cracks in freezing temperatures).

Unions, o-rings, fittings: Keep in a labeled bag or container in the garage/shed.

Equipment Covers

Pump cover: Waterproof tarp or purpose-made pump cover protects from snow, rain, UV exposure.

Filter cover: Tarp or tank cover (if available) prevents debris accumulation, UV degradation.

Heater cover: Optional as most heaters designed for outdoor exposure year-round, but cover extends lifespan.

Conclusion

Winterizing pool equipment requires removing all drain plugs from pump housing (typically 2 plugs), filter tank (1 plug), heater header (1-2 plugs), and any chlorinators or inline equipment, storing plugs in pump basket for spring retrieval, lubricating all o-rings with pool-grade lubricant preventing cold-weather cracking, blowing out plumbing lines with air compressor at 15-20 PSI until bubbles emerge from return jets then immediately installing winter plugs maintaining air lock, removing and storing salt cells indoors after cleaning calcium scale deposits to prevent freeze damage costing €300-800 replacement, and optionally storing pumps, cartridge filters, and other removable equipment indoors protecting from weather exposure. 

Portugal’s mild Mediterranean climate requires minimal winterization with coastal areas rarely experiencing freezing temperatures allowing a simplified approach of reduced pump runtime without complete equipment drainage, while interior regions should drain equipment as insurance against occasional cold snaps though underground pipes remain protected by earth insulation.