You will find the valve in the bottom of the S-bottle. Take this in your hands and squeeze the raised edge in the middle and push the ends together (or you can push a finger back once in the raised part). After this you will see a small air hole, see photo below the text.
Check whether the valve feeding is properly open. After cleaning, this can be closed again. Make sure that the valve is completely dry before you place the valve in the bottom. Press the valve firmly into the bottom ring. Do not screw the bottom tightly onto the bottle, hand-tightening is sufficient!
If the S-bottle sucks a vacuum, this usually means that the valve at the bottom of the bottle is not working properly. For the anti-colic S-bottle to function properly, it is important that the air hole in the valve is fully open!
Tip! While cleaning the S-bottle, you can easily remove the anti-colic valve under the tap. Turn the unscrewable bottom of the bottle and hold it upside down under running water. Thanks to the holes in the bottom of the bottle, the water flows against the valve and releases it easily. It is also possible to knock the valve out of the bottom.