You're right Brad, but I don't think that was the point. It seems like this approach is mostly theoretical, so I wouldn't expect real data anytime soon.
But that's ok, because there's a lot of theory to cover. I'd like to see an article that covers flow restriction calculations. I found an article (I don't remember where) that converts typically found items in plumbing, to a useful figure: head.
We all know that a pump can only lift/pull water to a certain height, but few of us have actually caculated the whole resistance of flow as a measure of that height. With that info, we'd know what to expect from a typical rig, and have a better idea about what pump to choose.
The article does mention some figures about flow rate versus effective temps, and so it seems that a rig should be flowing at least 30 gph. Anything less becomes exponentially less efficient. Anything more becomes exponentially irrelevant.
Using 30 GPH (which in itself is still debatable), and that 5 psi pressure is just about ideal for max flow rate through our tubing, we can then calculate the actual needed size of that tubing. As Una found out, bigger is not necessarily better.
Knowing the size of the tubing, and the overall flow resistance, we can then select an appropriate pump.
(and for the kiddies out there running an Eheim 1250, no, your flow rate is NOT actually 317 gph).
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