Quote Originally Posted by UNTAMED View Post
-putting a pump up and one down cuts resistance in half\50% does it not ?
-where I,m at loss is that it's greater than 32'[I think] is the max any pump in the world can draw [@sea level?],so how -say a 2psi drop on the block's\tube relate[down-up]- scaled down in a closed loop on these low pressure pumps.
The resistance of a loop is the same no matter where you put the pumps. Think of it as pressure gains and pressure losses. The pumps are both pressure gains, any tubing or blocks are pressure losses.

Here's one weird thing:
*Water flowing UP a vertical tube incurs a pressure LOSS of the pressure of a water column the height of the tube PLUS the pressure loss of the tube.
*Water flowing DOWN a vertical tube incurs a pressure GAIN the pressure of a water column the height of the tube MINUS the pressure loss of the tube.

Which means a vertical loop, is exactly the same as a horizontal loop. Remember that absolute pressure usually doesn't matter, provided you don't do what the OP did and get the pressure so low that atmospheric pressure crushes your tubing. This is why siphons work.

Most of this is irrelevant since, from the pics he's posted, the OP's layout is completely flat.

Also remember that you can't have a block so restrictive that NO coolant flows. (well, you can, it's just a completely plugged one). Fluid resistances are dependent on the flow rate, so as the flow rate drops, so does the resistance.