dart pump question

[BlueAbyss]

Originally Posted by hillegom

From the Reef Aquarium, by delbeek and Sprung vol 3 2005
Page 111 table 3.4
For every 1.5 in 90 deg elbow The extra resistance in thermoplastic pipe in feet is like adding 4 extra feet of pipe.
Let me restate
Adding a 90 deg elbow into 1.5 in pipe increases the resistance of the water as if you added 4 more feet of pipe.
How much resistance equivalent to feet of head, depends on the volume or g/hr you are pushing with the pump

So what you are saying is that a pump that pushes less volume will have less loss in a 90 degree elbow, all other things being the same? ie: A 1000 gph pump pushing water through a 1.5" 90 degree elbow will incur less losses than a 2000 gph pump?

For some reason that seems right, relating to some reading on fluid dynamics I've done... Can't remember exactly, but there's some sort of mathematical equation for that sort of thing... I don't have the book anymore, either, can anyone clarify this?

Anyhow, I would go ahead and use spaflex, just to avoid all of this... you will still incur some loss but 90 degree elbows are really really bad for friction losses because of the turbulence in the sharp corner of the bend.

+1 on using gate valves, and having some back pressure on the pump will not only make it run quieter but (I may have read somewhere) may make it consume less power.