River tank set up, advice on flow please?

[Direwolf82]

The manufacturer would be able to tell you what the pump can do at a particular head pressure, they have some nice graphs that showing flow rates at different head pressure. They use straight piping with no bends or elbows of any kind at zero head, general rule of the thumb is each soft(curved ninety, not a hard ninety) ninety degree fitting in line loses about three percent flow 45 degree fittings are much better at around one percent but still not great. Vinyl tubing is theoretically the best but the insert fittings reduce the pipe i.d. so much it is like having an extra three 90's in a row. And with different kinds of pumps like high volume low pressure (hvlp) pumps and the opposite high pressure low volume pumps it gets interesting picking the right overall pump.
At best these are ballpark figures, there are entirely to many variable when it comes to sizing pumps and water speed. Pipe distance and head pressure can change everything but there are ways to pipe it that make less work for the pump and therefore can achieve slightly higher flow rates, albeit with a slight drop in pressure. Also depending on what type of material used and smoothness of pipe walls will affect the water friction coefficient as well as what fitting are used and if they are properly glued in without any gaps or ledges between end of the pipe and inside of the fitting. Then we can get into the drag coefficients for the tank and decorations and etc, if you really want to get into hydraulics and fluid dynamics then we need to factor in for the coreolus and venturi effects thought the tank and piping.
I was really just looking for a simpler way to approximate water speed through the tank, thanks to all who took the time to chime in and help out. KEEP THEM FISH SMILING!!!