The pressure release valve isn't fully sealed. This happens if the lid isn't locked or the sealing ring is compromised.
- Turn off the heat. Let the cooker cool completely.
- Open the lid. Check the silicone sealing ring around the underside of the lid. Ensure it's seated correctly in its groove and free of food debris or damage.
- Close the lid. Align the arrow on the lid with the unlock symbol on the pot handle. Turn the lid clockwise until the arrow aligns with the lock symbol. You should feel it click into place.
- Ensure the pressure regulator (the weighted valve) is clean and placed correctly on the vent pipe.
IF THAT DIDN'T WORK: The sealing ring might be worn or damaged. It's a replaceable part. A damaged ring cannot create an airtight seal, causing constant hissing.
HEADS UP: Never force the lid closed or try to cook if it won't lock smoothly. Always start with a cool, clean cooker and ensure the rim of the pot and lid are clean and dry before sealing.