2. Apply a little saliva or soapy water to the valve. If a bubble forms, the valve should be tightened with the back of the cap.
Attention! Only metal caps are suitable for tightening the valve stem. Metal caps are sold at petrol stations.
3. Check the valve again. If a bubble forms again or the valve no longer tightens, it should be replaced.
4. Be sure to screw the cap back into place.