Quote Originally Posted by bigslappy View Post
planning on a huge resevior on the loops out lines of the PC on that same level as the PC = I'll get a 7 foot drop',,,,
planning on PVC pipe about 10 t0 8 inches wide & then just keep reducing down the size with reducers to 1 1/2 pipe then tee it back into two loops agin reduce agin into the rads that way i'll get water pressure to the rads in the crawlspace by gravity & by reducing the pipe size in incurments that increases the water pressure with no pump , then it's into a pair of pumps straight outaa the rads up & 2 more pumps at the PC into the water block loops for MAX flow
It does not matter (from a pressure perspective) how wide the pipes are. Pressure only depends on height (it is a measure of Force pre Unit AREA) and as the RAD will be relatively restrictive, compared to 1/2" pipe, you will not see a noticeable difference in flow due to larger tubing.

Just use the same size pipe for the whole thing, should be a lot easier.