How to Do Plumbing on Drains & the Angles You Need

Draw a rough diagram of the plumbing plan, to show the routing for pipes from a sink to a main drain. Locate cabinet sides, walls and other obstructions that the pipes must go through or around. Indicate the angles for connections, to go around obstacles or just veer from a center sink drain to a line inside a wall. Locate vents; all plumbing drains must vent to the outside or be equipped with special interior venting.

Check plumbing supply houses for angled connectors, at 90-degree, 45-degree or other angles. Use a tape measure to figure the distances for straight run pipes between connectors, from a kitchen sink, for instance, to a pipe leading to the main drain. Mark all the connections on your plans, showing every turn. Cut PVC pipe for straight runs to length with a hack saw and connect it with the appropriate angled fasteners.

Combine elbows and angled connectors to work around obstacles horizontally and go down through walls to main drains. Form almost any shape by blending angled and elbow connectors, with straight pipes between as needed to extend an elbow or angle.

Dry fit pipes together to make sure all the elements fit. Remove sections one at a time and cement them with PVC cement; apply cement to the outside of one element, the inside of the connecting piece, slide the two together, twist them slightly, then let the cement set. Use cemented connections up to the point under a sink or other drain where you will install a P-trap.

Install P-traps, actually U-shaped pipes, with screw-on compression connectors under every sink or other basic drain point. Buy the P-trap of the correct size for the pipes being drained. Slip the pipe from the sink or other drain into one end of the P-trap and fasten it; the connector has a plastic washer that expands to seal the joint between the two pipes. Put the pipe leading to the main drain in the other end of the P-trap and fasten it.