What does error code HF mean on a Hayward pool heater?

Flame with gas valve off. Flame is present while the gas valve isn't energized.

Can I fix Hayward code HF myself?

Start with these safe checks: Turn the heater off at its control and shut the gas valve to the heater. Shut it down and call a qualified tech. Don't run it again until it's checked.

When should I call a technician for code HF?

Shut it down and call a qualified tech. Don't run it again until it's checked. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

Hayward Pool Heater Error Code HF: Flame with gas valve off

What HF means

Flame is present while the gas valve isn't energized.

Likely causes

Gas valve not closing
Flame sensing fault

Safe first checks

Turn the heater off at its control and shut the gas valve to the heater.

When to stop

Shut it down and call a qualified tech. Don't run it again until it's checked.

Checked against: Hayward Universal H-Series heater troubleshooting guide (UHS16b): diagnostic codes. Codes can differ by model and year, so confirm with your owner's manual.