It is not necessarily the slits are too big. It is smaller slits produce smaller bubbles. It is just the smaller slits are better in that they produce smaller bubbles that move more water compared to longer or larger slits or openings. Both can work, but one is more efficient. As an example, remove the diffuser and have the air escape from the hose undiffused that produces really large bubbles. This way produces lots of noticeable surface action, but it is even less efficient at moving water than that of a larger slit diffuser.
The upwelling of water around 5" above the surface is a feature of using or having larger bubbles and and also a feature of placing the diffuser in shallower water. The surface action of larger bubbles will produce more noticable surface disturbance but not necessarily move more water. Finer bubbles do not cause more visible surface action than the larger bubbles. The larger slit diffuser will work okay, just not as efficiently as a finer bubble diffuser.
A way to test the amount of or speed of water moving away from the diffuser is to measure how fast an orange or similar mostly submerged object will move away from the boil. An object completely or fully floating on the surface does not really accurately reflect the current movement below the surface. This is a simple method used to measure stream flow.
Gluing or affixing the perimeter of the diffuser to a adjacent surface will make it more diffucult to disassemble the diffuser or change the membrane.
Last edited by Bill Cody; 08/08/17 03:42 PM.
