Plumbing a Kitchen Part 4 of 5
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.
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
Step 1
How to Install DWV Pipes for an Island Sink
Install the base cabinet, then insert the drain and vent pipes through the holes in the cabinet floor, and solvent-glue the pieces together.
Step 2
Air Admittance Valves
The loop vent is approved by code in any jurisdiction and is a reliable way to vent your island sink. But in many parts of the country, you’ll find another option that is far simpler, if not as time-tested: the air admittance valve (AAV). Invented in the 1970s, AAVs let the necessary amount of air enter a DWV system when water is draining, but they close when the line has emptied to keep sewer gases from escaping.
The advantage of AAVs is that you can install them to vent individual fixtures, reducing the amount of vent piping needed, as well as the number of roof penetrations. You can also install them on branch vent lines to service more than one fixture.
Be sure to check with your local building department before installing them anywhere. Any vent system containing AAVs also must have at least one standard vent outlet to the exterior of the building.
The first AAVs on the market were spring-activated, and you can still purchase these today through wholesale plumbing suppliers or the Internet. Later versions are gravity activated. In these AAVs, the valve is opened by negative line pressure in the drain line created by flushing or draining. When the valve opens, the pressure in the line equalizes.
AAVs can be installed into PVC systems like any other solvent-glued fitting. Always install AAVs according to the manufacturer’s specification.
Air admittance valves are designed to allow air into the vent system when needed, but to keep it from exiting when the system should remain closed.
Step 3
Air Admittance Valves
The original air admittance valves were spring loaded (right) but advancing technology is replacing these versions with gravity-activated AAVs (left).
Step 4
Common AAV Applications
By installing an AAV in a plumbed kitchen island, you can do away with almost all of the complicated loop-vent plumbing. But be sure to check with your local plumbing inspector first. AAVs are allowed in all 50 states but not in some municipalities in selected states.
Step 5
Common AAV Applications
An AAV connected to the trap of an individual plumbing fixture can eliminate great amounts of vent-plumbing work. In many large public stadiums, for example, each bathroom fixture is vented with an AAV to cut down on the number of long vent runs.
Step 6
Common AAV Applications
An AAV can be installed on a branch drain servicing as many as six fixtures (check local code), as long as the DWV system has at least one outlet through the roof and outside of the building.
Step 7
How to Install New Supply Pipes
Drill two 1"-diameter holes, spaced about 6" apart, through the floor of the island base cabinet and the underlying subfloor. Position the holes so they are not over floor joists. Drill similar holes in the floor of the base cabinet for the wall sink.
Step 8
How to Install New Supply Pipes
Turn off the water at the main shutoff and drain the pipes. Cut out any old water supply pipes that obstruct new pipe runs, using a tubing cutter or hacksaw. In our project, we removed the old pipe back to a point where it was convenient to begin the new branch lines.
Step 9
How to Install New Supply Pipes
Dry-fit T-fittings on each supply pipe (we used 3⁄4" x 1⁄2" x 1⁄2" reducing T‑fittings). Use elbows and lengths of copper pipe to begin the new branch lines running to the island sink and the wall sink. The parallel pipes should be routed so they are between 3" and 6" apart.
Step 10
How to Install New Supply Pipes
Solder the pipes and fittings together, beginning at the T-fittings. Support the horizontal pipe runs with copper pipe straps attached to the joists at least every 6 ft. (Check your local codes for specific strap spacing requirements.)
