Running Drain Lines

Installing a Kitchen Drain-Waste-Vent System

Installing a new drainpipe

Draw a plan for a new drainpipe showing how it will be vented and where it will connect to the drain-waste-vent system. Have your plan approved by a local plumbing inspector.

A kitchen usually does not have a 4-inch line that requires a thick wet wall as in a bathroom. Kitchen plumbing sometimes runs through an exterior wall, but pipes should be well insulated. In areas with cold winters, run supply pipes up from the basement through the floor rather than through the wall.

Remove all cabinets that are in the way. Completely cover all cabinets and flooring that you will reuse to protect them.

If wiring is in the way, shut off the power to the circuit and test to make sure power is off. You may want to remove a cable before working on the drain.

Prestart Checklist

Time
About a day to run a new drain line with a revent

Tools
PVC saw or circular saw, level, layout square, drill with hole saw, reciprocating saw

Skills
Cutting and joining PVC pipe, running pipes through walls, connecting new pipe to old

Prep
Clear the room of all obstructions; have your plans approved by an inspector

Materials
PVC pipe and fittings to suit local codes, PVC primer and cement, fitting for joining to the drainpipe, pipe straps

Previous | Next

Step 1

Once you've put together a dry run of the drain and vent lines, mark for cutting holes in the framing. Using a layout square, strike a line even with the top of the pipe. Then mark for the center of the pipe at the center of the stud.

Previous | Next

Step 2

For running 2-inch pipe, use a 2-1/2-inch hole saw to drill through the studs. When possible, cut until the guide bit pierces the stud, then cut from the opposite side. Assemble the pipes in the wall, notching the studs where necessary.

Previous | Next

What If... You install a sink in an island?

A sink installed in a kitchen island poses a special problem because there is no easy way to tie into a vent. The solution is a loop vent. This is a complicated setup, so consult an inspector after you draw up your plans. The drainpipe is run in the standard manner -- a 1-1/2-inch trap linking to a 2-inch sink drain that runs down to a 3- or 4-inch drainpipe by means of a sanitary tee. The vent pipe first loops up as high as possible, then runs down and over to a suitable vent pipe run up a wall. Because some water will likely enter the vent pipe, it also must be connected to the drainpipe using a sanitary tee fitting.

Step 3

Having used the dry run to mark the existing stack, add braces and pipe straps to stabilize the drain. Then cut away a section to make way for the new installation.

Previous | Next

Step 4

If the stack is ABS (shown in Step 3) or cast iron, use short lengths of PVC pipe and no-hub fittings to connect a sanitary tee for the vent and a Y-fitting and 45-degree street elbow for the drain. Then mark and cut a section of 2-inch PVC pipe to complete the stack.

Previous | Next

Step 5

Install a brace for the supply drop ears. Mark, prime, and cement the drain-vent system.

Previous | Next