Newbie plumbing question. Any reason to go from 2" pipes to 1 1/2" (don't have any choice) and then back to 2" ?

[michelb]

Hi, we have to change our filter and salt cell unions so I need to change some of the plumping (inground pool).

I'm going to go from the pump to the filter using 2" but then from the filter it goes to the roof and our solar heater which is all 1 1/2" (and I'm not going to replace it) and then from the roof (1 1/2") it goes to the salt generator cell which then splits and goes to the 2 jets in the pool. Once it comes back down from the roof, is there any value going back to 2" through the cell and then to the split (which will be 1 1/2" again afterwards). The pool return line is 2" from the skimmer to the pump. Or should I just do 1 1/2 from the roof solar and on ...

Let me know what you think. Thanks,
Mike

(In case it makes any difference, Intelliflo VF pump, Hayward C3040 cartridge filter, Jandy Aquapure 1400 salt gen. 16x32 inground pool maybe 7-8' deep end - maybe 20k gallons (I'm really not sure))