Unlike having a kitchen sink installed against the wall, plumbing required by an island sink is not as simple. You are unable to hide vents and drain pipes inside the wall, as it all needs to be enclosed within the island.
Although plumbing arrangements for an island sink may require a bit more preparation and expertise, it can be done by homeowners who possess basic plumbing tools as well as a little experience.
You can also save some money by doing this setup yourself.
Air Admittance Valve or Island Vent?
You'll need to ensure sewer gases don't come up the pipe and stink up the kitchen. For this reason, you'll need an air admittance valve (AAV) or underground vent. Whenever wastewater flows down the pipe, the valve will open and stop the escape of sewer gases.
If you wish to have a dishwasher connected to your island sink, an air admittance valve may be over-worked. Therefore, you should consider using a vent rather than a valve if high water volumes will be run down the sink frequently. However, the AAV is suitable for most homeowners. The following instructions will guide your AAV installation.
Before you begin, confirm that your municipal code permits the use of an AAV.
Island Sinks: Determine Your Pipe's Path
Run your two inch drain pipe underground to the cabinet where your island sink is from the main waste stack of the kitchen. Ensure this is the shortest possible path before you begin removing your flooring to install the pipe.
After the pipe has been brought into the cabinet, it will need to be extended to a point below the sink bottom, about five inches.
Fix the Drain
Attach the drain and tailpiece of the island sink. The tailpiece will be attached to your P-trap assembly. Attach your PVC extension pipe to the P-trap's other end.
Shift the P-trap until its extension touches the drain pipe as well. Here, you'll mark the point where both pipes intersect.
At this intersection point, cut the drain pipe using a hacksaw. Use sandpaper to get rid of any burrs.
Place your sanitary tee in a way that the sweep faces up and the outlet points in the direction of the P-trap. The outlet and extension pipe has to be the same size. Fit the sanitary tee firmly to the drain pipe using PVC cement.
Attach the tee and extension pipe. Cut the extension pipe if it is too long to properly fit in the tee's outlet. Attach both with PVC cement. The top of the tee will still be left open.
Fix the Air System Valve
You can use the cut-out piece from the drain pipe to put into the tee's top. It may be possible for you to glue it to the piece of pipe, depending on your AAV type. Otherwise, a threaded adaptor may need to be installed and the valve screwed in.
To wrap up, carefully clean up any PVC cement that may have squeezed out from the pipe fittings and allow it dry.
It can be somewhat challenging to install an island sink, but a homeowner with the know-how can do this without getting an expert plumber. If you encounter any problems or need to fix a more conventional vent, however, get help from an expert.