= volume of water coming out of pool
=Volume of water going into pump
=volume of water coming out of pump
=volume of water going into filter
=volume of water coming out of filter
=Volume of water going into pool
They are all the same since you don't have leaks in your system
Granted velocity is different and pressure is different
For all practical purposes it doesn't matter long as you meet the requirements for installation, mounted horizontally with a certain inlet and discharge distances of straight pipe