Plumbing a Kitchen Part 3 of 5

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Plumbing a remodeled kitchen is a relatively easy job if your kitchen includes only a wall sink. If your project includes an island sink, however, the work becomes more complicated.

 

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Overview

Plumbing a remodeled kitchen is a relatively easy job if your kitchen includes only a wall sink. If your project includes an island sink, however, the work becomes more complicated.
An island sink poses problems because there is no wall in which to run a vent pipe. An island sink requires either a complicated configuration known as a loop vent or a device called an air admittance valve (AAV), now approved by most codes. An AAV eliminates the need for a loop vent in most island sink installations. Check with the local plumbing inspector before designing an installation with an AAV or a loop vent.
For our demonstration kitchen, we divided the project into three phases:
• How to Install DWV Pipes for a Wall Sink
• How to Install DWV Pipes for an Island Sink
• How to Install New Supply Pipes
Our demonstration kitchen includes a double wall sink and an island sink. The 1 1⁄2" drain for the wall sink connects to an existing 2" galvanized waste-vent stack; since the trap is within 3 1⁄2 ft. of the stack, no vent pipe is required. The drain for the island sink uses a loop vent configuration connected to an auxiliary waste-vent stack in the basement.
From: The Complete Guide to Plumbing, 978-1-58923-378-2

What You'll Need

Tools:

Drill
Screwdriver
Reciprocating saw
Ratchet wrench
Pipe
Banded couplings
Tubing cutter or hacksaw
Solvent glue

Materials:

Drill
Screwdriver
Reciprocating saw
Ratchet wrench
Pipe
Banded couplings
Tubing cutter or hacksaw
Solvent glue

 

Step 1

How to Install DWV Pipes for an Island Sink

In the basement, establish a route from the island vent pipe to an existing vent pipe. (In our project, we used the auxiliary waste-vent stack near a utility sink.) Hold a long length of pipe between the pipes, and mark for T-fittings. Cut off the plastic vent pipe at the mark, then dry-fit a waste T-fitting to the end of the pipe.


Step 2

How to Install DWV Pipes for an Island Sink

Hold a waste-T against the vent stack, and mark the horizontal vent pipe at the correct length. Fit the horizontal pipe into the waste-T, then tape the assembly in place against the vent stack. The vent pipe should angle 1⁄4" per foot down toward the drain.


Step 3

How to Install DWV Pipes for an Island Sink

Fit a 3" length of pipe in the bottom opening on the T-fitting attached to the vent pipe, then mark both the vent pipe and the drain pipe for 45° elbows. Cut off the drain and vent pipes at the marks, then dry-fit the elbows onto the pipes.


Step 4

How to Install DWV Pipes for an Island Sink

Extend both the vent pipe and drain pipe by dry-fitting 3" lengths of pipe and Y-fittings to the elbows. Using a level, make sure the horizontal drain pipe will slope toward the waste-vent at a pitch of 1⁄4" per foot. Measure and cut a short length of pipe to fit between the Y-fittings.


Step 5

How to Install DWV Pipes for an Island Sink

Cut a horizontal drain pipe to reach from the vent Y-fitting to the auxiliary waste-vent stack. Attach a waste-T to the end of the drain pipe, then position it against the drain stack, maintaining a downward slope of 1⁄4" per foot. Mark the auxiliary stack for cutting above and below the fittings.


Step 6

How to Install DWV Pipes for an Island Sink

Cut out the auxiliary stack at the marks. Use the T-fittings and short lengths of pipe to assemble an insert piece to fit between the cutoff ends of the auxiliary stack. The insert assembly should be about 1⁄2" shorter than the removed section of stack.


Step 7

How to Install DWV Pipes for an Island Sink

Slide banded couplings onto the cut ends of the auxiliary stack, then insert the plastic pipe assembly and loosely tighten the clamps.


Step 8

How to Install DWV Pipes for an Island Sink

At the open inlet on the drain pipe Y-fitting, insert a cleanout fitting.


Step 9

How to Install DWV Pipes for an Island Sink

Solvent-glue all pipes and fittings found in the basement, beginning with the assembly inserted into the existing waste-vent stack, but do not glue the vertical drain and vent pipes running up into the cabinet. Tighten the banded couplings at the auxiliary stack. Support the horizontal pipes every 4 ft. with strapping nailed to the joists, then detach the vertical pipes extending up into the island cabinet. The final connection for the drain and vent loop will be completed as other phases of the kitchen remodeling project are finished.


Step 10

How to Install DWV Pipes for an Island Sink

After installing flooring and attaching cleats for the island base cabinet, cut away the flooring covering the holes for the drain and vent pipes.


 
 

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