I've gone through the check valve discussion before. I use them and others don't. People have blasted me before about them and I dont care. Ive never had a failure with one because I properly maintain them/replace them regularly. But lets not make this a discussion here. I just want to fire my brain cells about the cons of this set up
I never wear a seatbelt, I just don't use them. People blast me for it and I don't care. I have never been hurt in a car accident so I don't waste my brain cells worrying about it.
Dank: You may or may not care and you may or may not maintain your check valves. But the simple reality is that if you rely on a check valve to prevent flooding, then you are on the very short side of the odds. You can't cheat the physics or the probability, no matter how lucky you have been.
Your false sense of security derived from luck and turning a blind eye to the facts with regard to check valves is rather congruent with your desire to move forward with an "upside down" tank. That is, to move forward with such a plan, you need to turn a blind eye to the the reality that the system will be hard (if not impossible) to maintain in a reasonable way AND no matter what measures are taken, there is an extremely high probabilty of system failure resulting in catastrophic consequences for the building, livestock and/or system components.
In other words, from a physics standpoint an "upside down" system will work just fine (when it is working). From a realistic standpoint, opperation and maintence of the system is riddled with problems. Just because we can do things does not mean we should.
It is not clear if this project is YOURS or for somebody else. If it is for you and in your space, have fun
. If it is for somebody else, I certainly hope that you are very honest about the scope and probabilty of problems with every aspect of the system. Customers often trust the opinion of "experts" without realizing that the said expert "doesn't believe in seatbelts because they have never been hurt in an accident". Cases in point: Just about every system built on "tanked" is a real world nightmare that is either highly prone to catastrophic failure or nearly impossible to maintain. Don't be that guy (company).
Reading through this thread it appears (and again in context with your check valve statement) that you are turning an blind eye to the big picture. This is a far cry from a cup in a bath tub. You are talking about a 4,000 gallon system that will rely on maintenance of a negative pressure vessel that must be plumbed AND kept clean AND have 4,000 gallons of extra drain down capacity.
I realize that air entering up there should be removed though it doesn't really need to be. Even in the event that some air gets up there the vacuum still holds. How would a return constantly add air there? Unless im running my sump dry there is no possible way to introduce air into the system unless somewhere in my plumbing there is a hole.
Last I checked, gasses are disolved on our tank water and tend to come out under negative pressure. Moreover, living things exhale or produce gasses as part of their biological existance. Air bubbles will accumulate constantly at the top.
