Originally Posted by jsutter71
I am not happy or unhappy with my current flow. I was mostly looking for comparisons from other people to determine whether or not I should add another pump. As far as my goal is concerned, I want to be able to have flexibility with my pumps. Given the choice and budget, I would rather have three pumps running at 50% to obtain the same results as two running at full power.
Here we go. These are approximate figures for you restriction curve but you will get the point. The curves for the D5 numbers (1x, 2x, 3x pumps) are exact (save minor differences in adding pump in series). the traced line is your flow with 2x D5 running at 100% (around 1.2 GPM). You can clearly see that even if you run your 3 pumps at 100% you will gain very little in total flow (the point where the blue line cross the 3x pump pressure drop curve) because restriction increase exponentially with flow.
You can do the same calculation for 3x d5 running at let's say 40% if you want (just need to put both of yours d5 running now at 40% to check the flow and approximate the exponential curve using the new traced line).
so bottom line here: you would probably not gain much adding a third pump and to known how much would you gain by been able to run the 3 pumps at lower rpm you would need to estimate the restriction with pumps running at lets say 40 or 60%
numbers came from here:
and a useful reading (which you might already have):
https://martinsliquidlab.wordpress.com/pump-planning-guide/Edited by Gabrielzm - 7/19/16 at 4:28pm