flow for closed loop

[sphelps]

For the intake you'll want dual 2" lines, not 1.5" if you're running a dart. Large strainers are key as that can be the biggest problem for restriction.

The amount the OM will restrict your flow will depend on the original flow rate but I find then pretty restrictive overall, I'm considering removing mine for this reason plus the timing motor tends to squeak, the drum jams up sometimes and it's a pain to maintain in tight spaces.

Personally if it were me I'd skip the OM and but two pumps instead. Plumb one pump to pull water from one side of the tank and push water in the other side. Plumb the second pump the same but opposite. Then use couple timers or a single timer and a NC+NO relay to switch between the pumps every hour or so. This way you get true alternate flow, less restriction and redundancy.