Trying to design and build a system where water pump into multiple outlets (pvc) evenly
In general to get the water to flow evenly to all three outputs you have to ensure that all the paths from the pump to all three outputs is the same including length. In addition what ever nozzle or outlet opening you have has to be exactly the same for all three. To achieve this you will have to split the three outlet flow pipes before you get to the outputs. Something like this:



I have made the above sketch to show how the paths from the split point to the outlets is the same length.

Now with that said if the distribution pipe inside diameter is large compared to the outlet nozzle and the pressure inside the pipe has a significant drop across the nozzle then the pipe path similarity and length as stated is less significant. What that means is that the manifold type outlets like you show in your drawing would work if they are close together and the pump maintains a head of pressure in the lines. 

On the other hand if ends of the delivery pipes to the outlets is just an open ended pipe then the similarity of the paths will be important to achieve the same flow at each output.