One carbonator (A+B) is used to sparkle each 750ml (25.4oz) bottle. The carbonator is poured into the interior carbonation chamber through the top funnel hole. When you pull down the handle, the interior carbonation chamber is sealed and some water is pumped from the back water reservoir into the carbonation chamber. CO2 gas is created and sent to the bottle for pressure infusing and sparkling the contents of the bottle.
After the carbonation cycle, the handle is lifted which seals and releases the bottle so you can either open it now or place the sealed bottle in the refrigerator for later. The handle also releases a valve on the bottom of the interior carbonation chamber. The pressure in the system pushes the carbonator residue into the residue drawer. This residue drawer can be pulled out and emptied. It holds the residue from up to 7 carbonation cycles. The residue can be poured down the drain of your sink. The carbonator residue is safe to handle and safe to pour down the drain.
For those interested in the chemistry, the carbonators are made of two small sachets, one containing sodium bicarbonate and the other containing citric acid. When they are combined with water, they produce CO2 gas. The gas is pumped away to the bottle and the liquid residue which remains is water and dissolved sodium citrate. The water and dissolved sodium citrate are poured down the drain from the residue drawer.
Sodium bicarbonate, citric acid and sodium citrate are commonly found as food ingredients and in antacids. They are safe to handle, however, they can be potential eye irritants. Avoid contact with your eyes. If they get in your eye, rinse your eye with water.
Top Appliance Parts - referenced in this article & in the image below:
(5) Top funnel & top funnel hole.
Appliance Parts - Referenced in this article & in the image below:
(3) Handle, (5) Residue drawer, (10) Water reservoir.