S-trap for a bath tub drain. Tub Drain Repair:

Installing An S-Trap In A
Bath Tub Drain

In This Article:

An S-trap and an elbow are used to connect a new tub drain to an existing drain line.

Related Articles:
Skill Level: 2 (Basic) Time Taken: About An Hour

By , Editor


After the new tub drain had been installed, there was a vertical pipe to connect to the drain system.


The existing drain pipe (red arrow) lay about 12 inches below the new drain. Existing tub drain line and new tub drain pipes, to be connected.


One part of the repair: a 90 degree elbow.

This is a slip-joint fitting. This type of fitting is used under basins and tubs because it is adjustable, removable and easy to install. The large threaded nuts compress a soft plastic tapered gasket, (or ferrule) which squeezes firmly against the pipe to make a water-tight seal.


The S-trap kit came with a long section of 1-1/2" PVC tube. I cut off a little piece to attach to the elbow.


The purpose of the short straight piece is to connect to the threaded adapter on the existing drain pipe.


This is an S-trap.


The trap can easily be positioned to fold back on itself, allowing it to fit in a tight space, or to connect two vertical pipes that are fairly close together.


I used another short piece of 1-1/2" pipe to attach to the outlet of the trap.


I connected the trap to the tub drain (top of photo) and then to the elbow (kind of hidden from view).


Another view of the scene, showing the tub overflow tube and S-trap. Old tub with new drain and S-trap.


I replaced the cut-out section of bottom plate with a new piece of 2x4.

I also supported the drain pipe with a piece of steel perforated strap.


The procedure in this article was a repair to an old house that did not meet today's plumbing codes, because the drain system was not vented properly. In fact, the house shown here had NO VENT at all, which explains why the drains always gurgled whenever the water was run.

The procedure shown here would not meet plumbing codes in most places in the United States and Canada, where a "P"-trap that connects to a vented vertical drain line would normally be required. Water in an "S"-trap can easily be siphoned out by lack of proper venting

We used an "S"-trap to rebuild the drain lines on this bathtub because it was simple, it fit in the available space, and we could reach it from the small access opening. Before doing this project there was no trap at all. Needless to say, the house is a piece of junk... literally a textbook of code violations.

For exact code requirements, we recommend consulting a licensed plumber or your local plumbing inspector.

Read Replacing Sink Drain Plumbing for information about adding a vent where none existed before.



Tools Used:

  • Basic Hand Tools
  • Small Saw

Materials Used:

  • 1½" PVC S-Trap
  • 1½" PVC 90º Elbow Slip-Joint Fitting


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Copyright © 2001, 2005 HammerZone.com

Written February 11, 2001
Revised January 12, 2005