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.
Adjust the filling head to fit the syphon, and fasten by means of the set screws. Place the syphon in the machine and close the screen. With the foot on the treadle force the nozzle of the syphon bottle into the filling head, and hold it firmly in that position while filling. Pull the lever of the filling head towards you, thus opening the water valve, and when the water stops flowing, on account of the compressed air in the syphon, open the air valve by forcing the lever from you, allowing it to close quickly. The air being thus allowed to escape, more water will enter the bottle upon again opening water valve. If the water stops flowing into the bottle before it is full, open the air valve again and allow more air to escape. Never commence to fill a syphon until it has been carefully covered with the screen. Do not fill the syphon more than four- fifths full. Allow sufficient space for gas, enough to discharge the syphon satisfactorily. In taking the filled bottle out of the filler, raise the foot quickly to avoid escape of gas. The best pressure for filling syphons is 120 to 140 pounds. A rubber hose connected with the air-escape valve leads off the water, which may be ejected with the air without sputtering.