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Winterizing Pool Heaters

Comprehensive winterization for gas, electric, heat pump, solar, and hybrid heaters - prevent $1,500-$4,000 freeze damage.

When to use: Pool heater needs winterization to prevent freeze damage to heat exchanger or heating elements.

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Winterizing Pool Heaters

Comprehensive winterization for all heater types - gas, electric, heat pump, solar, hybrid

$$$

Freeze Damage: $1,500-$4,000 Repair Cost

Water expands 9% when frozen. Trapped water WILL crack heat exchangers, rupture titanium coils, and destroy heating elements. Complete drainage is critical.

Estimated Time by Heater Type

Gas heater: 30-45 min • Heat pump: 45-75 min • Solar: 60-90 min • Electric: 20-30 min • Hybrid: Add times for each system

Critical Safety & Warranty Rules

• GAS: ALWAYS shut off gas supply AND verify pilot is out (gas leak = explosion risk)
• ELECTRIC: ALWAYS verify power is off before removing drain plugs (electrocution risk)
• HEAT PUMP: NEVER skip drain plugs (freeze damage voids warranty on most brands)
• SOLAR: NEVER exceed 10 PSI when blowing out panels (tube rupture voids warranty)
• ALL TYPES: NEVER add automotive antifreeze (toxicity and warranty void)
• ALL TYPES: NEVER seal heater completely (condensation causes corrosion)
• Document winterization date for warranty compliance if required

Quick Reference: Heater Type Identification

GAS: Has gas line connection, burner tray visible through vent, pilot light or electronic ignition. Loud when running. Brands: Raypak, Pentair, Hayward, Jandy.

HEAT PUMP: Large fan on top (like AC unit), no gas line, refrigerant lines visible. Quiet compressor hum. Brands: Hayward, Pentair, Raypak, AquaCal.

SOLAR: Panels on roof or rack, no gas/high voltage power. Controller with sensor. Silent operation. Brands: Heliocol, Fafco, SunGrabber.

ELECTRIC RESISTANCE: High voltage (240V+), heating elements inside tank/chamber. No gas, no refrigerant. Rare in residential. Brands: Flowline, Chromalox.

Identify Your Heater Type & Model

Different heater technologies require dramatically different winterization procedures.

GAS HEATERS: Raypak, Pentair MasterTemp/Max-E-Therm, Hayward H-Series, Jandy LXi/JXi

ELECTRIC RESISTANCE: Flowline, Chromalox, Mega-Flow (rare in residential)

HEAT PUMPS: Hayward HeatPro, Pentair UltraTemp, Raypak R6350ti, AquaCal

SOLAR: Roof-mounted panels (Heliocol, Fafco, SunGrabber) with controller

HYBRID: Combination gas + solar OR heat pump + gas backup

Locate model number plate (usually on front or side panel)

Download manufacturer manual if you don't have it (search model number + PDF)

Note: Failure to winterize correctly can void warranty and cause $1,000+ damage

Gas Heater Winterization

Prevent freeze damage to heat exchanger and ensure safe shutdown.

Turn OFF gas supply at manual valve (quarter-turn lever perpendicular = off)

Turn OFF heater at control panel and set to 'Off' mode (not standby)

Turn OFF power to heater at dedicated circuit breaker

Remove drain plugs from heat exchanger (typically 2 plugs, 1/4" NPT)

Open pressure relief valve to allow air entry (aids drainage)

Tilt heater slightly if possible to drain all water from heat exchanger

For copper heat exchangers: ensure complete drainage (copper cracks easily when frozen)

For cupro-nickel exchangers (salt pools): check for corrosion while exposed

Add 1 cup pool antifreeze through drain ports if complete drainage uncertain

Leave drain plugs OUT all winter (store in ziplock bag taped to heater)

Cover heater top vent with screen or cover to prevent debris/nests (not airtight)

Do NOT seal heater completely (condensation causes corrosion)

For millivolt systems: verify pilot light is completely extinguished

For electronic ignition: disconnect low-voltage control wiring if rodent risk

Heat Pump Winterization

Critical winterization - heat pumps are most vulnerable to freeze damage.

Turn OFF heat pump at control panel (set to 'Off' not 'Standby')

Turn OFF dedicated circuit breaker (prevents accidental startup)

CRITICAL: Remove ALL drain plugs from heat pump body (typically 3-5 plugs)

Locate plugs on: inlet/outlet headers, condensate drain, base pan, compressor housing

Tilt unit forward 2-3 inches to drain all water from titanium heat exchanger

For units with automatic drain valves: manually open and verify drainage

Inspect titanium exchanger for scale buildup (white/gray deposits)

Clean evaporator coil fins with gentle spray (removes debris and pet hair)

Lubricate fan motor if applicable (check manual - some are sealed bearing)

Cover condenser coil with breathable cover (not plastic - causes moisture trap)

For inverter heat pumps: disconnect power completely (protects electronics)

Add 1-2 cups antifreeze through drain ports (insurance against trapped water)

Store drain plugs in labeled bag attached to unit

In harsh climates: consider building wind shelter around unit (plywood barrier)

Never wrap heat pump in tarp or plastic (condensation causes corrosion and mold)

Solar Heater Winterization

Drain panels completely to prevent freeze damage and panel rupture.

Turn OFF solar controller or set to 'Winter Mode' if available

Close ball valves isolating solar panels from main circulation

Remove solar panel drain plugs (usually at panel manifold low points)

Open air relief valves at panel high points (allows complete drainage)

For roof panels: gravity drains most water, but some water remains in tubes

Use air compressor at 5-10 PSI to blow remaining water from panels (low pressure!)

NEVER exceed 10 PSI when blowing out solar panels (tubes rupture easily)

For Heliocol/Fafco panels: expect 5-10 gallons of water to drain from typical system

For SunGrabber/flat panels: check for standing water in header pipes

Disconnect sensor wiring if rodents are a concern in your area

Leave panel valves OPEN (allows any remaining water to expand safely)

Do NOT add antifreeze to solar panels (voids warranty and clogs tubes)

Inspect panel mounting brackets and roof penetrations for leaks

Clean debris from panel surface (leaves block sun and accelerate degradation)

For glazed collectors: check glass for cracks, replace damaged panels

Document sensor placement for spring reconnection (take photos)

Electric Resistance Heater Winterization

Simple winterization but element damage is expensive if done wrong.

Turn OFF heater at control panel

Turn OFF dedicated breaker (high voltage - typically 240V single phase or 3-phase)

Verify power is off with non-contact voltage tester (safety critical)

Remove drain plugs from heating chamber (typically 2 plugs, bottom of tank)

Open pressure relief valve if present

Allow complete drainage (may take 10-15 minutes for full flow to stop)

Inspect heating elements for scale buildup (white crusty deposits)

If heavy scale present: soak elements in CLR overnight, rinse thoroughly

Check element resistance with multimeter (consult manual for spec)

Failed elements: resistance = infinite or very low (short circuit)

For flow-through heaters: ensure flow chamber is completely empty

Leave drain plugs OUT all winter (store with heater manual)

Cover electrical connections with plastic bag to prevent moisture entry

For outdoor installations: cover heater with breathable tarp (not sealed)

Winterize Heater Plumbing & Bypasses

Protect valves, bypasses, and associated plumbing from freeze damage.

Identify heater bypass valve configuration (3-way, 2-way, or manual ball valves)

For 3-way valves: set to full bypass mode (water bypasses heater entirely)

For 2-way valve systems: close heater inlet valve, open bypass valve fully

For manual ball valves: close both heater inlet and outlet, open bypass to full

Verify water can circulate through bypass when main pump runs (prevents freeze)

Blow out heater inlet/outlet lines with compressed air (15 PSI)

Add 1 cup antifreeze to inlet line (pour into pipe at heater connection)

Check all unions and connections for cracks or wear while exposed

Lubricate valve O-rings and stems with silicone-based lubricant

For automated valves (Jandy, Pentair): disconnect actuator power, manually position valve

For pressure switches: disconnect and store indoors (prevent corrosion)

For flow switches: verify paddle moves freely, clean debris

Inspect PVC unions for cracks (replace if brittle or cracked)

Take photo of valve positions for spring startup reference

Winterize Control Systems & Sensors

Protect electronics, thermostats, and safety sensors from weather damage.

Turn OFF all heater control power at breaker (prevents phantom loads)

For digital controllers: remove batteries if battery-backed (prevents corrosion leaks)

Disconnect low-voltage sensor wiring (prevents moisture damage to control boards)

For wireless thermostats: remove from outdoor location, store indoors

Remove water temperature sensors from plumbing (prevents freeze damage)

Clean sensor probes with soft cloth (improves accuracy and lifespan)

For freeze protection sensors: leave connected if main pump will run in winter

For high-limit switches: verify operation before shutdown (prevents spring damage)

Inspect wiring conduit for cracks or damage (repair before spring)

For Pentair EasyTouch/IntelliTouch: set to 'Service Mode' to preserve settings

For Hayward Omni: enable 'Winter Mode' in settings (disables heater functions)

For Jandy AquaLink: disconnect heater from system config (prevents error codes)

Document all sensor locations with photos (makes spring reconnection easier)

Store sensors in dry location (basement or garage, not outdoor shed)

Hybrid System Special Considerations

Systems with multiple heat sources require coordination of winterization steps.

GAS + SOLAR HYBRID: Winterize both systems using respective procedures above

HEAT PUMP + GAS HYBRID: Winterize heat pump first (more sensitive), then gas

Ensure bypass valves route around BOTH heat sources

For priority systems: verify control logic is disabled (prevents startup attempts)

If only one heater winterized: reconfigure valves to bypass inactive heater

Solar + gas: typically only solar needs full winterization (gas can run in winter)

Heat pump + gas: winterize heat pump, leave gas operational if pool stays open

Update controller programming to disable winterized heat source

Add notes to control panel identifying which heaters are winterized

For tri-hybrid systems (rare): consult professional if unsure of procedure

Document valve configuration with photos (complex systems hard to remember)

Final Inspection & Spring Preparation

Verify complete winterization and prepare for easy spring startup.

Verify ALL drain plugs are removed and stored in labeled containers

Verify ALL power is off at breakers (use non-contact voltage tester)

Verify gas supply is off and pilot lights are extinguished (gas heaters)

Place bright tag on breaker panel: 'Pool Heater - OFF for Winter'

Take comprehensive photos of all valve positions and configurations

Create spring startup checklist NOW (easier than recreating from memory)

Document any maintenance issues noticed (scale, corrosion, worn parts)

Order replacement parts now (drain plugs, O-rings, gaskets) - 6-8 week lead time

For warranty equipment: log winterization date in warranty records

Set calendar reminder for March/April to order parts before pool season

Store all manuals, photos, and parts in labeled folder or box

If professional service required for startup: schedule NOW (April is booked early)

Inspect heater pad for gas leaks one final time (soapy water test)

Cover heater vents with mesh screen only (prevents nesting, allows ventilation)

Common Questions

Can I just add antifreeze instead of draining?

No. Antifreeze is supplemental insurance, not a replacement for drainage. Most heaters hold 1-3 gallons of water. Antifreeze would need to be 50% concentration to protect that volume - prohibitively expensive and potentially damaging to seals. Always drain completely, then add antifreeze to protect residual water.

What if I lost the drain plugs from last year?

Order replacements immediately (most are 1/4" or 3/8" NPT brass plugs). Available at pool supply stores, hardware stores, or manufacturer websites. Keep spares in your pool supply kit. In emergency, use NPT brass plugs from hardware store (match thread size). NEVER use PVC plugs (crack when tightened).

My heat pump has an "auto drain" feature - is that enough?

No. Auto drain valves release condensate during normal operation, but don't fully evacuate heat exchanger for winter. You must still manually remove all drain plugs and tilt unit for complete drainage. Auto drain helps, but isn't sufficient alone.

Can I run my gas heater periodically during winter?

Yes, IF pool remains operational and plumbing is not winterized. Gas heaters can safely run in winter if water is circulating. Heat pumps should NOT run below 45-50°F (efficiency drops to zero and compressor damage risk increases). Solar can't run if panels are drained.

How do I know if water is completely drained?

After removing drain plugs, wait 10 minutes for initial drainage to stop. Then tilt heater slightly - more water should drain. If tilting produces no additional water, drainage is complete. Final test: blow compressed air through drain port - should exit opposite port with no bubbling (bubbling = water present).

What's the difference between cupro-nickel and copper heat exchangers?

Copper: Used in chlorine pools. More vulnerable to freeze cracking. Turns green/blue when corroded. Cupro-nickel: Used in salt pools. More expensive, corrosion-resistant. Gray/silver color. Both require complete drainage for winter. Cupro-nickel is less forgiving of incomplete drainage due to higher cost to replace.

Climate-Specific Guidance

Northern States (Zone 3-5: below 0°F winters):

MANDATORY complete winterization. All heater types must be fully drained, with antifreeze added. Heat pumps especially vulnerable - don't skip any steps. Solar panels must be blown out with compressed air. Consider indoor storage for expensive control electronics.

Mid-Atlantic/Midwest (Zone 6-7: 0-20°F winters):

Full winterization recommended. Gas heaters can sometimes run if pool stays open, but must be drained during cold snaps. Heat pumps should be winterized (not cost-effective below 50°F anyway). Solar requires full drainage.

Southern States (Zone 8-9: occasional freezes):

Partial winterization acceptable if pool remains open. Gas heaters can run all winter. Heat pumps effective Oct-April. Drain heat pumps only if multi-day freeze forecast. Keep drain plugs accessible for emergency drainage. Solar may not require winterization if no freeze risk.

Sunbelt (Zone 10+: frost-free):

Winterization generally not required. Regular maintenance and cleaning sufficient. Gas heaters rarely needed. Heat pumps can run year-round (most cost-effective heating). Solar provides free heating in winter. Maintain equipment normally, inspect annually.

Checklist

1Identify heater type - gas, electric resistance, heat pump, solar, or hybrid system.
2Gas heaters: Shut off gas, turn off power, remove drain plugs, blow out heat exchanger.
3Heat pumps: Remove ALL drain plugs, tilt to drain titanium exchanger, never skip steps.
4Solar panels: Close isolation valves, blow out at 5-10 PSI max (tubes rupture easily).
5Electric resistance: Verify power OFF, drain completely, inspect elements for scale.
6Winterize heater plumbing - set bypass valves, blow out inlet/outlet lines.
7Protect control systems - disconnect sensors, remove batteries, store electronics indoors.
8Hybrid systems - winterize each heat source using appropriate method, coordinate valves.
9Document setup with photos, create spring startup checklist, order replacement parts.

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