I purchased this sink pump that will pump up about 8 feet. Is it really necessary to run a 1.5" drain and a 1.5" vent? That seems like very large PVC, would it hurt if I went down to 1.25" or so? The reason I ask is I drilled 2" holes in my ceiling and am having a hard time flexing the 1.5" PVC into place. I know I could always buy flex PVC but if I can save $100 by just using 1.25" that would be nice.