I'm running a 1 1/2 inch pvc piping as my drain and return plumbing, my question is will I need to use any type of adaptors to connect to a return pump and what size pump should I run on my 180 gallon ?
That depends on where the sump is located. Decide on what flow rate you want, then look at various pumps to see which ones will give you that flow against the pressure head you will have. I have a ReefFlow Hammerhead on my sump. The sump is in the basement, and the display is on the first floor. The pump has a 1 1/2" outflow, so it is no problem to connect to the 1 1/2 inch return line. I think I calculated that the maximum flow with my set up is around 1500 gph against a 15' water column (I put this together several years ago, and may not remember the figures exactly).