Spa Not Heating Properly

Troubleshooting a Spa That Won’t Reach the Right Temperature

If your spa isn’t heating properly—or stops heating altogether—there are several common causes. Some issues are simple to check, while others require professional diagnosis. This guide will help you identify possible reasons and what to do next.

⭐ 1. Check Your Heater or Heat Pump Settings (Most Common)

Many spa heating issues come from settings that were changed, reset, or accidentally switched.

What to check:

✔ Spa mode actually turned ON

✔ Set temperature higher than current water temperature

✔ System not stuck in POOL mode

✔ Automation schedule not overriding your command

✔ Freeze protection mode not active

On Hayward automation, make sure “SPA” is glowing/highlighted and target temp is set correctly.

⭐ 2. Spa Is Losing Water to the Pool (Return Valve Issue)

If valves aren’t positioned correctly, the spa will not heat—it will just circulate cooler pool water.

Signs:

• Spa level dropping while running
• Water flowing into the pool from the spa spillway
• Temperature rises very slowly or not at all

Fix:

• Check that both suction and return valves are set to SPA
• Make sure no water is spilling into the pool during spa mode
• If valves are automated, verify actuators are moving correctly

A malfunctioning actuator can prevent proper spa isolation.

⭐ 3. Dirty Filter Restricting Flow

Low flow = heater won’t fire or heat pump won’t activate.

What to check:

✔ Filter pressure higher than normal

✔ Cartridge dirty or clogged

✔ Pump speed set too low

Fix:

• Clean the cartridge
• Raise pump speed in spa mode
• Backwash (for sand/DE systems)

If flow is too low, most heaters will shut off for protection.

⭐ 4. Air in the System

Air in the spa line can prevent the heater from operating properly.

Signs:

• Bubbles in pump basket
• Pump not fully primed
• Return jets weak in spa mode

Fix:

• Raise water level
• Clean baskets
• Lubricate pump lid O-ring
• Check for suction leak

⭐ 5. Heater Not Starting (Gas or Electric)

If the heater does not ignite or heat pump does not start:

Check for:

✔ No power to heater

✔ Tripped breaker

✔ Thermostat set too low

✔ Gas valve turned off (gas heaters only)

✔ Error codes on heater or automation panel

If you see an error like LO, FLO, IF, IGN, or HS, the heater detected a problem and shut down for safety.

⭐ 6. Heat Pump Issues (If You Have a Heat Pump)

Heat pumps depend on warm outside air. They will not heat efficiently in cold or windy conditions.

Common causes:

• Outside temperature below operating range
• Low refrigerant
• Dirty evaporator coil
• Blocked airflow
• Running at too low of a pump speed

Fix:

• Run at full pump speed in spa mode
• Keep area around heat pump clear
• Avoid running during very cold mornings/nights
• Schedule service if cold-air short cycling occurs

⭐ 7. Spa Jets Not Diverting Properly

If the jets are not providing strong flow:

✔ Heater may not activate

✔ Spa may heat unevenly

✔ Temperature rises very slowly

What to check:

• Diverter valves pointed correctly
• Spa jets open (many twist to open/close)
• Suction valves in correct position
• Dirty filter reducing jet pressure

⭐ 8. Aged Heater (10+ Years Old)

Heaters naturally wear out. Common failure points include:

• Burned-out igniter
• Faulty thermostat
• Internal scale buildup
• Bad pressure switch
• Failing gas valve
• Corroded heat exchanger

If your heater is over 8–12 years old, repair may not be cost-effective.

⭐ 9. When to Contact Professional Pool Company

You should contact us if:

✔ Spa is stuck below 90–95°F

✔ Heater shows error codes

✔ Water spills into pool during spa mode

✔ Automation valves are not turning

✔ Pump speed changes don’t help

✔ You smell gas (turn system OFF immediately)

✔ Heat pump runs constantly but water won’t warm

We can inspect your heater, pump, valves, actuators, and automation system to identify the exact cause.

⭐ Summary

A spa that won’t heat properly usually indicates:

• Incorrect valve/automation settings
• Low water flow
• Air in the system
• Heater ignition issues
• Heat pump limitations
• Aged heater components

Most issues are solvable quickly once the cause is found.

⭐ Need Help?

If your spa still won’t heat after these checks, contact Professional Pool Company. We’ll diagnose the issue and get your spa heating correctly.

Updated on: 29/11/2025