Special Request: Drain question from Dave

Written by Mike Johnson in Bathroom, Design

Dave from Watertown called about a problem with sewer gas coming from a drain. During the phone call he explained the problem and we determined the drain didn’t have a vent the proper distance from the trap. The drain line is 2″.

Hello Dave!

Per Wisconsin state code the vent for this fixture needs to be within 8′ of the trap and no closer than twice the diameter of the drain. For this application what you need is a 2″ x 2′ x 1 -1/2″ T fitting. In the photo provided I’m holding the “T” fitting you need exactly as it should be installed. The term a plumber uses is “a T on it’s back”.  Basically, it just means that the 1-1/2″ hub on the fitting needs to be pointed straight up towards the sky. The reason why it’s important to install it like this is because the vent needs to be dry and this keeps the air movement positive and out of the way of the drain itself.

In the photo you can see where I had drawn some arrows. The horizontal arrow is the direction of flow. Notice how the “T” has a slight radius to the vent? It’s not a life or death situation but it’s considered good plumbing practice to orientate the fitting in the best possible fashion. In the photo you will also notice how I held the fitting at a slight angle to show the drain slope, I did this just to show what it will look like after you install it.

The vertical arrow shows the vent portion of the “T”. Like I said earlier this needs to be installed straight up. During the install it’s best to have a small level with you. When you glue the fitting set the level on the 1-1/2″ hub and you’ll be in great shape.

Next, simply tie in the vent. Per the phone call I would use a mechanical vent.

It’s that simple Dave. Just take your time and have fun with it. Once you install the vent your drain system will work very well. It’s best if you install the “T’ about 2′ from the trap if possible. Good luck, let me know if you have any installation problems.

Mike

Tags: bathroom, Drain, plumber, vent