Always shut the valve that is closest to the inside plumbing, and don’t shut the valve that is closest to the street. If the room where the sink will be installed has supply valves, you can shut them off instead. They’ll be on the water pipes, but this isn’t always an option.
To figure out which pipe is which, consult the house’s blueprint or listen as water flows through the pipe. The drain pipe flows away from the building. If the pipe is overhead, such as in some basements, purchase a sink sump pump from the home improvement store.
If your drain pipe is cast iron, it’s better to buy a rubber wye fitting and solder the pipes together instead of gluing them.
The wye fitting should be positioned so the small, unattached opening faces towards where your sink will go.
The vent pipe helps the sink drain and prevents sewer gas from entering the house.
If you’re using a sump pump, connect it to the vent and drain pipes according to the owner’s manual. [7] X Research source
You may also use a hammer and nail to tap the holes into the wall.
Wipe away any excess putty that oozes from the strainer.
