Quote Originally Posted by bluehaze View Post
No not exactly, a Y halves the restriction by converting 1 intake path into 2. There is a resistance at the inlet of the Y but as long as that inlet is the same size at whats feeding it it does not add any restriction at all.
True, but in your case, your inlet is the size of the 1 fitting hole coming out of the pump. All you're doing is taking that flow and dividing it into 2 paths.

The T3 doesn't have that limit, since it has a big chamber, and 2 ports exiting from a chamber that was tuned to do so. And an even bigger chamber on the inlet side.

Quote Originally Posted by bluehaze View Post
In otherwords the only time a Y will pose a restriction (in a computer loop) is when turning 2 sources into one. (For instance turning both loops back into one before dumping back into the res) It will never pose a restriction when turning one source into 2 (At the beginning of a loop feeding two sepearate loops) as long as that restriction is greater than the restriction at the inlet of the Y.
True again, but you're not gonna gain anything. Your flow was sorta already capped by the pump exit itself, and the diameter of the inlet to the Y.

Take your garden hose (one connected to a house), and put one of those Y splitters on it. Run one hose full open (no nozzle), then do them both at the same time. Whats gonna happen? Soon as you open the 2nd one, your gonna drop in pressure, and the water is gonna come out the hoses slower.