Quoted from: http://www.aquariumplants.com/THE_BEST_Check_Valve_medical_grade_p/check12.htm
""THE BEST" Check Valve (medical grade)(.017 psi CRP)
After years of experience with Co2 systems, we finally discovered why consistant "bubble counts" are, most of the time, impossible. Here's why: ALL checkvalves, even expensive ones, have a "high crp pressure" or "crack pressure" rating (the pressure at which they actually release) and/or a very inconsistant "crp" pressurre" rating. We actually took a "caliper" and measured the Co2 tubing at different times and what we found is this: The tubing is actually a "long balloon"... When pressure builds in the tubing (because of a high crp rating of the CV) Co2 is "stored up" in the tubing, until the CV opens. Then it releases, then it build up again, and more or less "cycles". What you experience is a very inconsistant bubble count. This Checkvalve is "medical grade" (imported from Germany) and the best CV available."
Hum ... What do you think about this thing?
- How does it keep water from backing up into the regulator assembly when the CO2 is off? Is it designed for running the CO2 24/7?
- Notice the silicone tubing ... silicone tubing is a "weak balloon!" Why not use stronger tubing like one with thicker walls? Clippard, Tygon Lab, etc. It wouldn't be needed, would it? This "weak balloon" reminds me of an intestine.
- "high crp pressure" or "crack pressure" rating ... I know that check valves do have a pressure at which the valve cracks open, but this cracks me up for some reason. I can visualize it squeezing itself together, straining until it can't hold it anymore and suddenly the gas is released. (Did) somebody step on a duck?
- It has a digital face measuring the distance that its "jaws" are open, I believe. Doesn't tubing stretch and deform over time and render this measurement less meaningful?
- Or, is there a microprocessor in it to control "pulses" in the CO2 supply?
PS: Does seeing CO2 consistently spelled Co2 make you wonder about what "years of experience" really means?