How to Install Sink Drains Without a Vent Pipe

Sink drains typically need a vent pipe if the drain causes water hammer or other plumbing noises when operated. This is not the case for all homes today, so many drains are installed without a vent pipe. If you are taking on this task there are a few things to note, but the process is fairly similar to installing a drain with a vent pipe. In fact, there are fewer steps to complete in this project.

P-trap (sink drain)
Wrench
Reducing connector
Slip joint washer
Pipe, 1 1/2-inch (length depends on your plumbing set up)

Instructions

- 1
  Fit the slip joint washer and nut over the end of the drain pipe on the bottom of the sink and slide it up about 3 inches. This washer and nut is included with your p-trap drain, available at any hardware store.
- 2
  Place the longer end, which is the top end, of the p-trap over the sink drain pipe and thread the slip joint nut on the p-trap. Tighten this nut by hand and then with a wrench, moving the nut another quarter turn or so after it is sufficiently hand tightened.
- 3
  Fit a reducing connector to any home drain pipes that are larger than 1 1/2 inches in diameter with another slip joint nut and washer. Tighten the connector by hand and with the wrench.
- 4
  Connect a 90-degree fitting to the other end of the p-trap to the home's drain pipe by placing a slip joint washer and nut on the end of the fitting and attaching it to the p-trap. Tighten the connection by hand and the wrench again. If necessary, install a length of pipe to bridge any gaps between the p-trap and home drain line.

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