Quote Originally Posted by Snyxxx View Post
The problem is the inlet for the other pump does not connect directly to the pump volute. The inlet from the reservoir sort of pushes close to the inlet of the pump, but not actually connected. This is more like a waterfall than a direct connect.

If you look at the picture long enough, I think the inlet tube has a gap at the inlet of the pump.

You will not get the pressure benefit of a series setup.
Because pressure (outside the bounds of the component's native pressure drop vs. flow curve) cannot be lost in an equilibrium system, you'll have one of two things happen.

1) the res will fill to max capacity and they'll behave exactly like serial pumps (water is incompressible). Though this is the case of separated reservoirs.

2) it'll just behave 'right.' The water leaving will have the pressure and flowrate of two pumps in serial since that's how they're arranged. Yes, even with that little gap between pump inlet and the feed-line's outlet, it works just fine. It's practically the same with the 'old' XSPC res tops.

There's a lot less voodoo in watercooling than is assumed