🌡️

Pool Heater Not Heating

Heater runs but water temperature not rising

5,100
Monthly Searches
Flow Issues
Most Common
Urgent
Fix Priority
$150-600
Repair Range

Quick Answer

Pool heaters that run but don't heat usually have flow problems (45%), thermostat issues (25%), or heat exchanger problems (20%). Check for high filter pressure restricting flow, verify thermostat settings, and ensure bypass valves are closed. If water flow is good but still no heating, call professional for internal component diagnosis.

Understanding "Heater Runs But Doesn't Heat"

What This Means

  • Power is working: Heater turns on and shows it's running
  • No temperature rise: Pool water stays cold despite heater operation
  • System appears normal: No obvious error messages or shutdowns
  • Wasted energy: Heater consumes gas/electricity but produces no heat

Why This Happens

  • Heat not transferring: Water not flowing through heat exchanger
  • Thermostat problems: Not calling for heat when needed
  • Bypass issues: Water flowing around heater instead of through it
  • Internal failures: Heat exchanger or heating elements damaged

Southlake, Westlake, Grapevine Pool Note: During Texas winter, heaters run longer but if water isn't heating, you're wasting hundreds of dollars in energy costs while your pool stays unusable.

Most Common Causes by Heater Type

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Gas Pool Heaters (Most Common)

Heat exchanger issues: Scale buildup or corrosion prevents heat transfer to water.

Common Gas Heater Issues:

  • • Calcium scale on heat exchanger coils
  • • Low gas pressure reducing heat output
  • • Restricted water flow through exchanger
  • • Thermostat not sensing water temperature

Southlake, Westlake, Grapevine Area Specific Problems:

  • • Hard water scaling (high calcium)
  • • Gas pressure drops during peak demand
  • • Wind affecting heat loss
  • • Seasonal operation stress

Electric Pool Heaters

Element failures: Heating elements burn out but heater still appears to run.

Electric Heater Issues:

  • • Burned out heating elements
  • • Scale buildup on elements
  • • Faulty contactors not energizing elements
  • • Low voltage reducing heat output

Texas Grid Issues:

  • • Voltage drops during peak demand
  • • Elements damaged by power surges
  • • High electrical costs making operation expensive
  • • Grid instability affecting operation
♻️

Heat Pumps

Refrigeration problems: Low refrigerant or compressor issues prevent heat generation.

Heat Pump Problems:

  • • Low refrigerant charge
  • • Dirty or frozen evaporator coils
  • • Compressor electrical problems
  • • Reversing valve stuck or damaged

Cold Weather Issues:

  • • Efficiency drops below 50°F ambient
  • • Defrost cycle problems
  • • Ice formation on coils
  • • Backup heat not working

#1 Cause: Water Flow Problems

Why Flow is Critical

Pool heaters need strong water flow (20+ GPM) to transfer heat effectively. Low flow causes heaters to overheat and shut down on safety, while no flow means zero heat transfer.

Flow Restriction Causes

Dirty Filter (Most Common):

High pressure reduces flow through heater

Bypass Valves Open:

Water flows around heater instead of through it

Pump Problems:

Low speed or cavitation reduces flow

Heat Exchanger Blockage:

Scale or debris restricts internal flow

Quick Flow Checks

  1. Check filter pressure: Should be under 25 PSI
  2. Feel return jets: Should have strong flow
  3. Listen to heater: Should hear water flowing through
  4. Check bypass valves: Should be fully closed
  5. Test pump speed: Should be on high during heating

Quick Test: Turn heater off and feel the return jets. If flow is weak, fix circulation before troubleshooting heater.

Heater Safety During Troubleshooting

  • Never attempt internal heater repairs - gas and electrical hazards
  • Always turn off heater before checking connections or components
  • Do not bypass safety switches or temperature controls
  • Check for gas leaks if working around gas heaters
  • Ensure adequate ventilation around heater during operation
  • Call professional for any internal heater diagnosis

If you smell gas: EVACUATE immediately and call your gas company's emergency line

DIY Troubleshooting Steps

Step 1: Verify Water Flow

📊

Filter Pressure

Under 25 PSI

💨

Return Jets

Strong flow

🔧

Bypass Valves

Fully closed

Pump Speed

High speed

🌊

Heater Flow

Water sounds

Step 2: Check Thermostat Operation

Temperature Test:

  1. Use accurate digital thermometer
  2. Test water temperature at heater
  3. Set thermostat 10°F higher than current temp
  4. Verify heater calls for heat
  5. Monitor for 15-20 minutes

Thermostat Issues:

  • • Sensor not in water flow
  • • Calibration drift over time
  • • Loose or corroded connections
  • • Bypass water affecting sensor
  • • Internal thermostat failure

Step 3: Inspect for Obvious Problems

Visual Check:

  • • Error codes on display
  • • Unusual sounds or smells
  • • Visible damage or corrosion
  • • Water leaks around heater

Valve Position:

  • • All heater valves open
  • • Bypass valves closed
  • • Return valve settings
  • • Isolation valve positions

Operation Signs:

  • • Heater firing/running sounds
  • • Warm air from gas heaters
  • • Display shows heating mode
  • • Water circulation through heater

Professional Heater Diagnosis

1

Verify Heater is Actually Running

Confirm heater is operating, not just turned on

⚠️ Warning: A heater that appears on but isn't firing indicates serious safety issues

2

Test Water Flow Rate

Ensure adequate water flow for heat transfer

⚠️ Warning: Low flow causes heater to overheat and shut down on safety

3

Check Thermostat Settings and Operation

Verify temperature control system is working

⚠️ Warning: Faulty thermostats can cause overheating or no heating

4

Inspect Heat Exchanger (Gas/Electric)

Check for scaling, corrosion, or damage

⚠️ Warning: Damaged heat exchangers can leak dangerous gases or cause flooding

5

Test Electrical/Gas Components

Professional diagnosis of heater internals

⚠️ Warning: Gas and electrical testing requires licensed technicians

When to Call a Professional

Call Immediately If:

  • • Good water flow but still no heating
  • • Heater shows error codes
  • • Unusual sounds, smells, or vibrations
  • • Thermostat appears faulty
  • • Gas or electrical safety concerns
  • • Heat exchanger scaling suspected

Professional Services:

  • • Internal component testing and diagnosis
  • • Heat exchanger cleaning and descaling
  • • Gas pressure and combustion analysis
  • • Electrical component testing and repair
  • • Thermostat calibration and replacement
  • • Flow optimization and system balancing

Heater Not Heating Repair Costs

🔧 DIY Attempt

Estimated Cost:$0-50
Time Required:2-4 hours
Difficulty:Moderate

⚠️ Risks:

  • Missing internal component failures requiring professional diagnosis
  • Potential safety hazards with gas or electrical systems
  • Wasted time if problem is heat exchanger scaling
  • May need professional service anyway for complex issues

👷 Professional Service

Service Cost:$150-600
Completion Time:Same day diagnosis and repair

✅ Includes:

  • Complete heater system diagnosis
  • Heat exchanger inspection and cleaning
  • Thermostat testing and calibration
  • Gas pressure and electrical testing
  • Flow optimization and system balancing
  • Component replacement if needed

Detailed Cost Breakdown

Item/ServiceLowHigh
Service call and diagnosis$125$200
Thermostat replacement$150$300
Heat exchanger cleaning$200$400
Internal component repairGas valve, elements, etc.$250$600
Total Range$725$1500

💰 Value Tip: CoOpPools offers transparent pricing with no hidden fees. Our worker-owned model means fair prices and invested service.

Preventing Heater Efficiency Problems

Regular Maintenance

  • Clean filter regularly: Maintain proper water flow
  • Annual heater service: Professional cleaning and testing
  • Check valve positions: Ensure proper flow routing
  • Monitor thermostat accuracy: Test with reliable thermometer
  • Keep heater area clear: Proper ventilation and access
  • Test operation early: Before swim season starts

Southlake, Westlake, Grapevine Area Specific Prevention

  • Hard water treatment: Prevent heat exchanger scaling
  • Surge protection: Protect from Texas grid instability
  • Seasonal startup service: Professional system activation
  • Pool cover use: Reduce heat loss and operating costs
  • Wind protection: Shield heater from strong winds
  • Early problem detection: Address issues before damage occurs

This Issue Requires Professional Service

Pool heater not heating properly wastes energy and money while keeping your pool unusable. Our certified heater technicians quickly diagnose flow, thermostat, and internal component problems to restore efficient heating and get your pool warm again.

Mention "heater efficiency issues" when calling for faster service

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