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The plunger at the bottom of the sample tube can be in two positions. It can be pulled down, or pushed in. Most of the time, it should be pulled down. Some people forget which position it should remain in, so remember, "For most of the show, it hangs low".
On the very top of the sample tube is a white button. Pressing this down forces foamy liquid to spray out. Make sure the small capillary tube, extending from the top, points into a jug or bucket. You can see a small capillary tube leading away from the white button on the top.
The sample tube is also known as a cellar buoy.
Air pump
The black boxes fixed to the wall are air pumps.Specifically, this is a Flojet Diaphragm air pump. We are told:
The G57 Series of pumps can operate on air or CO2,
have a max pressure of 6.9 Bar and a max flow rate of 18.9 litres per minute.
They also feature an automatic on-demand supply and a range of diaphragm materials including Santoprene, Viton and Kalrez.
The G70K202A model is also ATEX approved.
An innovative compact design features a patented shuttle valve that eliminates stalling and provides a long life.
Using the image below, you can disentangle the wires. From every keg, there are two tubes. One feeds directly into the black air pump; the other into the junctions on the top row.
At the top of the image, we can see these "junctions". It looks like two tubes come out at the top, and one tube enters at the bottom.
Every air pump (big black box) has four tubes coming out of the bottom. Let's consider the centre one. One tube goes up (to the "junctions") and one down (to the horizontal tubing at the bottom). A third tube connects into the cellar buoy while a fourth is connected to the keg.
