New to forum, 24 years of pool ownership

[trebuchet]

We have been in our house for 24 years. Our pool is a 20 X 40 concrete pool.
I have been working over the years on doing upgrades as this pool is about 30 years old.

[Watermom]

Hi and welcome to the Pool Forum! Did you have any questions that you needed help with? Hope you enjoy being a part of our forum.

[trebuchet]

My pool has 1 1/2" piping to the main drain, pool return, spa drain and spa return. But the skimmer line is 2". In the pool shed the skimmer stays 2" all the way to the pump. But, the pump output to filter and all the return lines are 1 1/2".
now I want to re-plumb my pool shed to get rid of the globe valves and make the system simpler.
My question... Why is the skimmer line wider than the rest.
Also, is it a problem if I plumb 1 1/2" from the skimmer return to the pump. Basically, making the entire plumbing all the same.