flow for closed loop

[sphelps]

Originally Posted by FragIt Dan

Flow is relative to cross sectional area, so for 2" pipe it is 3.14x1^2= 3.14 vs 1" at 3.14x0.5^2=0.79, but two of them so 1.58. That puts it at 2:1. You would need four 1" return lines to prevent a bottle neck.

Velocity is relative to cross sectional area, in theory flow is the same no matter what but friction losses are greater with higher velocities but there are limits or critical velocities, eg pushing 200GPH though a 6" pipe won't make much difference over a 1/2" pipe. You can also drop the pi/4 when comparing ratios as it's a constant (just square diameters).

Also consider the pump Grizz uses is 1.5" in and out, the intake is one size up which is a good idea considering it's pretty restrictive. The output stays at 1.5" and then splits into two 1" lines at the OM, so at the output side it's pretty much 1-1. So to say there is a bottle neck isn't really correct, if that were true any pump that had a larger suction would have such design flaw.

That said it's still pretty restrictive plumbing which, like I said earlier, is typical with closed loops, especially with smaller tanks also containing a sump below. To say 3600GPH is going through it isn't very accurate, in the mid 2000s is probably more accurate. That combined with the return and flow probably sits pretty close to 20X. Would his LPS suffer if he dropped his turnover to 10X? Not likely.