Once you’ve figured out how to tie into your plumbing system and you’ve installed Ts or other fittings, you need to run the pipes. It’s easiest to run them in a basement or crawlspace, where they can hang below joists or inside walls, so you don’t have to cut into framing to make room for them. When you do run pipes in walls and joists, take care to make your holes and notches as small as possible, so you won’t seriously compromise your framing’s strength. Because the holes are not much larger than the pipes, they must be drilled at precise locations for the pipe to run in a straight line. In many cases, drilling holes in framing members is not a safe option, so check with your local building official if you are unsure. But if you’re ready to tackle the project, here are some helpful tips.
1. POSITION PIPES AND MARK WITH A SQUARE. Position the pipes where they will go, on the face of the framing. Use tape to hold them in place, and check that the horizontal lines are sloped down for the drain and up for the vent at about 1⁄4 in. per foot. Use a Speed Square® to mark a line even with the top of the pipe at each framing member.
2. MARK FOR PIPE AND STUD CENTERS. Measure the pipe’s outside diameter and divide in half to find the pipe’s center dimension. Cut a small piece of wood to that dimension and use it as a guide to mark each framing member. Then use a sliding square to mark the center of the stud; the intersection of the two lines is the center of the hole.
TIP: You can also mark for cutting holes using a long square, positioned at the center of the pipe diameters. The method shown on these pages takes more time but is more fail-safe, especially for do-it-yourselfers.
3. DRILL HOLES. Equip a right-angle drill with a hole saw that is about ½ in. wider than the outside diameter of the pipe and drill holes. The cordless drill shown here is powerful enough to drill seven or eight holes before the battery wears out, so keep an extra battery in the charger. If you have plenty of holes to drill, consider renting a corded ½-in. right-angle drill.
4. RUN PIPES WITH NOTCHES. Because you cannot bend the pipe, you will not be able to simply thread it through more than two holes in a row. There are two options: The first is to cut a notch in one or more of the studs.
OR USE COUPLINGS. The other method is to cut the pipe into sections short enough to thread through two holes, and use one or more couplings to join them together. When you do this, keep in mind that each coupling will add ½ in. or so to the length of the pipe.
5. PROTECT THE PIPES. Hammer on protective plates at each hole, to ensure that a nail driven through the future drywall cannot reach the pipe. If the studs are 2×6 and the framing member is at least 1½ in. thick at the hole, you are not required to do this.
Excerpted from Plumbing (The Taunton Press, 2016) by Steve Cory.
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