TL;DR: Replacing Pentair 79112700 120-volt 250-watt bayonet bulb takes 15-20 minutes. Turn off power at breaker, remove light from niche, remove lens, remove old bulb, install new bulb, reinstall lens, reinstall light, test operation. Bulb costs $25-$50 replacing burned out bulb. Proper installation ensures safe light operation. DIY installation saves $75-$150 service call cost.
SEO Summary: Complete 2026 guide to replacing Pentair 79112700 120-volt 250-watt bayonet pool light bulb covering tools required, power shutoff, light removal, lens removal, old bulb removal, new bulb installation, lens reinstallation, light reinstallation, testing, troubleshooting, and maintenance for reliable pool lighting.
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Table of Contents
Pool Light Bulb Overview
Pentair 79112700 is 120-volt 250-watt bayonet base incandescent pool light bulb. Bulb provides bright white light for pool illumination. Bulb costs $25-$50 replacing burned out bulb. Bayonet base twists and locks into socket. Typical bulb life is 1,000-2,000 hours or 1-2 years with normal use.
Note: LED bulbs are more energy efficient alternative to incandescent bulbs. LED bulbs cost more initially but last 10-15 years and use 80% less energy. Consider LED upgrade when replacing incandescent bulb. LED conversion provides long-term savings.
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Required Tools and Materials
Required tools: screwdriver (Phillips), towels, clean rags. Required materials: Pentair 79112700 bulb or compatible LED replacement. Optional: silicone lubricant for gasket.
Electrical Safety Procedures
Turn off power to pool light at circuit breaker. Verify power is off by attempting to turn on light. Never work on pool light with power on. Electrical shock in water is fatal. Power shutoff is critical safety step.
Wait 5 minutes after turning off power before removing light. Capacitors in light may hold charge. Bulb may be hot if recently operating. Waiting allows capacitor discharge and bulb cooling. Immediate work after power off risks shock or burns.
Work on deck not in pool. Remove light from niche and bring to deck for service. Working in water creates shock hazard. Deck work is safer and more convenient.
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Removing Light and Lens
Remove light mounting screw at top of light fixture. Screw secures light to niche. Turn counterclockwise to loosen. Set screw aside safely. Missing screw requires replacement.
Pull light fixture out of niche carefully. Light has 3-6 feet cord allowing removal to deck. Avoid pulling on cord. Support light housing during removal. Set light on towel on deck.
Remove screws securing lens to housing. Count screws ensuring all are removed. Typical light has 6-8 screws. Missing screw prevents lens removal. Set screws aside in container preventing loss.
Carefully remove lens from housing. Lens may stick from gasket. Gentle prying releases stuck lens. Avoid damaging lens or housing. Set lens on clean towel.
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Replacing Pool Light Bulb
Allow bulb to cool completely if recently operating. Hot bulb can burn hands. Wait 10-15 minutes for cooling. Cool bulb is safe to handle.
Remove old bulb by pushing in slightly and turning counterclockwise. Bayonet base unlocks with quarter turn. Pull bulb straight out of socket. Avoid touching new bulb glass with bare hands. Oils from skin shorten bulb life.
Inspect bulb socket for corrosion or damage. Corroded socket prevents good electrical contact. Clean minor corrosion with fine sandpaper. Severe corrosion requires professional repair or light replacement.
Install new bulb by aligning bayonet pins with socket slots. Push bulb into socket and turn clockwise quarter turn. Bulb locks into socket. Verify bulb is secure before proceeding.
Inspect gasket condition while light is disassembled. Cracked or hardened gasket requires replacement. Replace gasket preventing water leaks. Proper gasket ensures watertight seal.
Position lens on housing aligning with screw holes. Press lens firmly onto gasket. Install screws tightening evenly in star pattern. Even tightening ensures uniform gasket compression and watertight seal. Tighten until snug avoiding overtightening.
Testing and Light Reinstallation
Reinstall light in niche. Guide light carefully into niche avoiding cord damage. Position light flush in niche. Install mounting screw securing light. Tighten screw securely.
Turn on power and verify light operates. Light should illuminate brightly. Dim light indicates poor bulb contact or wrong bulb wattage. No light indicates bulb installation problem or electrical issue.
Monitor light for 24-48 hours checking for water entry. Inspect light housing through lens for water accumulation. No water confirms watertight seal. Water presence indicates gasket leak requiring lens reinstallation.
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Common Problems and Solutions
Light doesn't work after bulb replacement: indicates improper bulb installation or electrical problem. Verify bulb is locked in socket. Check circuit breaker. Test with known good bulb. Persistent problem requires professional diagnosis.
Light is dim: indicates wrong bulb wattage or poor socket contact. Verify bulb is correct wattage (250 watts). Clean socket contacts. Ensure bulb is fully seated and locked. Proper bulb and contact ensure bright light.
Bulb burns out quickly: indicates voltage problem or water in housing. High voltage shortens bulb life. Water in housing causes bulb failure. Address voltage or water problems preventing repeated failures.
Water in light housing: indicates gasket failure not bulb problem. Replace gasket ensuring watertight seal. Drain water and allow complete drying before installing new bulb. Water causes electrical problems and bulb failure.
Preventive Maintenance Tips
Replace bulb when it burns out. Do not delay replacement. Dark pool is safety hazard. Prompt replacement maintains pool safety and enjoyment.
Consider LED upgrade when replacing incandescent bulb. LED bulbs last 10-15 years and use 80% less energy. Initial cost is higher but long-term savings are substantial. LED upgrade is worthwhile investment.
Inspect gasket during bulb replacement. Replace worn gasket preventing water leaks. Gasket replacement during bulb change is efficient maintenance. Proper gasket prevents electrical damage.
Clean lens during bulb replacement. Remove calcium deposits and algae. Clean lens improves light output. Cleaning during bulb change is convenient maintenance.
Conclusion and Key Takeaways
Replacing Pentair 79112700 120-volt 250-watt bayonet bulb takes 15-20 minutes. Bulb costs $25-$50 with DIY installation saving $75-$150 service call cost. Proper installation ensures safe light operation and bright pool illumination.
Bulb is incandescent with 1,000-2,000 hour lifespan. LED bulbs are energy efficient alternative lasting 10-15 years. Consider LED upgrade for long-term savings and reduced maintenance.
Required tools include screwdriver and towels. Required materials include replacement bulb. Basic tools make this accessible DIY project for all pool owners.
Electrical safety procedures include turning off power at breaker, waiting 5 minutes before starting, and working on deck not in pool. Electrical safety is critical for pool light work. Never work on energized pool light.
Light and lens removal requires removing mounting screw, pulling light from niche, removing lens screws, and removing lens. Allow bulb to cool before handling. Hot bulb can burn hands.
Bulb replacement requires removing old bulb with quarter turn, inspecting socket, installing new bulb with quarter turn, and reinstalling lens. Avoid touching bulb glass with bare hands. Oils shorten bulb life.
Testing includes reinstalling light, turning on power, and monitoring for water entry. Bright illumination confirms successful installation. Water entry indicates gasket problem requiring correction.
Troubleshooting addresses light doesn't work, light is dim, bulb burns out quickly, and water in housing. Most problems result from improper installation or gasket failure. Systematic troubleshooting resolves most issues.
Preventive maintenance includes prompt bulb replacement, LED upgrade consideration, gasket inspection, and lens cleaning. Simple maintenance ensures reliable pool lighting and safety.
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Key Takeaways:
- Bulb costs $25-$50, DIY saves $75-$150 service call
- Installation takes 15-20 minutes
- Turn off power at breaker before starting
- Wait 5 minutes after power off before starting
- Work on deck not in pool
- Allow bulb to cool before handling
- Remove light mounting screw
- Pull light from niche to deck
- Remove lens screws and lens
- Remove old bulb with quarter turn counterclockwise
- Install new bulb with quarter turn clockwise
- Avoid touching bulb glass with bare hands
- Tighten lens screws evenly in star pattern
- Test light operation before regular use
- Consider LED upgrade for energy savings
- Inspect gasket during bulb replacement
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