PVC (AND ABS) pipes and fittings, once cemented together, stay that way, Unlike wood glues, which bind each piece of wood to it self, plastic pipe solvents actually melt one surface into the other, creating a chemical weld. With a 1-1/2-inch pipe and fitting, you'll have about 30 second's to change you mind about the joint. After that, it's permanent. So test-fit and mark each group of fittings with a pencil or felt-tip marker before gluing them in place.
When measuring for a pipe cut, be sure to include the depth of the fitting hubs in your total. You can make this calculation in your head, but holding an actual fitting in place helps to eliminate errors. When you've determined the exact pipe length needed, mark the pipe and cut it. You can use a hacksaw, handsaw(with miter box), PVC saw, wheel cutter, or power miter saw(cutoff saw).
Smooth the inside of the pipe end using a knife, sandpaper, or a deburring tool before cementing the joint together. Any rough edges will attract hair and strands of fabric sent though the system, causing clogs.
With the end of the pipe cleared of burrs and rough spots, apply primer-solvent to the outer edge of the pipe and to the hub of the fitting. Both primer-solvent and joint-cement containers come with applicators. When the prime evaporates, test-fit the joints, marking sure that the pipe bottoms out in the fittings. When you're sure the joints is right, mark the pipe to show where the fitting should land on it in final assembly. Next, coat the first 1 inch of the pipe and the entire inside of the fitting hub with cement. Lmmediately insert the pipe and fitting. As soon as the pipe bottoms out in the hub, rotate the fitting about one-quarter turn. This fills any voids in the joint by breaking up the insertion lines. Of course, if you've test-fitted your joint first, you'll need to push the pipe into the fitting with the alignment marks about the marks line up. Hold the parts together for about 10 seconds. Wipe off excess cement.