How important is it to actually maintain the recommended 2 ft/sec minimum flow velocity to entrain air bubbles? Some posts, both here and elsewhere seem to indicate a slower velocity is acceptable or even desirable. It seems like a pretty good balancing act between loop length, dT, and flow rate for a decent length of either 3/8 or 1/2 inch pex. ~900 feet total for the zone. ~18k btu design load for the zone For 1/2 inch pex, flow needs to be above 1.1 gpm which leaves a long loop length and the resulting high head, several short loops length and small delta T, or short length, low head, low flow. 3/8 pex drops the required flow nicely, while increasing head for the same loop length. Thanks.