sump plumbing

[PRAIRIESEA]

I just bought a hang on overflowfrom mike at blue world.It has a 11/2" apox600 gph bulkhead. and i'm getting aquagiant building me a
36"x18"x12" sump about 30g should i stay with 11/2" plumbing or can i to reduce it to 1". and were is a good place in edmonton to buy plumbig parts. by the way i have a 72g bow front with no over folw 2de 150w mh 2 t5 48" 54w blue actinc tubes corallife 220 skimmer.