I made a much modified reactor like that, using some smaller diameter clear PVC in the CO2 inlet area to serve as a built-in bubble counter. It was useless. Bubble counters only work if the very small diameter CO2 line releases the CO2 directly into the clear container, with nothing to interfere with the rising stream of bubbles. Otherwise the bubbles coalesce into giant bubbles, and other people's 3 bbs is 1 bubble every 5 seconds for you. Then the clear part of the reactor itself was always just a mass of roiling CO2 bubbles swirling all over the place, so it wasn't possible to do anything but see that the water had something in it. If I ever make another one, and I don't expect to, it will be white PVC, as simple as it is possible to make it.