This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Complaints are frequent that the pressure is lost from a fountain before its contents are drawn off. This is always caused either by the use of a poor washer between the cock and the top of the fountain, or by a failure to use the spanner wrench with sufficient force to make a tight joint. The gas may all escape without being manifested by appearance, in sight or sound. It cannot escape from the cock, for it would then drive the water before it and the leak would be apparent. Thick, soft, oil-tanned leather, such as harness makers use, should be used, and not the ordinary sole leather.
Sometimes shaking of the fountain may help, as carbonic acid separates from the water and increases the pressure on the latter. In case this manipulation is not sufficient, the pressure in fountain is too low and the fountain must be recharged and the leakage made tight.