• Piston valve is not installed properly.
• Airflow valve is not properly secured and directed upwards.
• Internal seal of air flow valve is clogged.
• The internal seal of the air flow valve is dirty.
• Airflow valve is broken.
• Tighten the piston valve securely or reinstall.
• Tighten the air flow valve securely and make sure it is facing up.
• Switch on the pump and let it work for a few seconds. Then switch off, repeat 3 times.
• Remove the air flow valve, remove the dirt with water and replace the valve.
• Replace with a new air flow valve.