The drain on this tub is working fine. Just wondering why it travels in a strange direction. Attached is a top view sketch.

[i93.photobucket.com]

This a single-story house on a concrete slab. I had to tear down a wall for another job, and happened to notice a big hole in the floor where the tub drain enters the floor. Not sure why it's open...maybe for easier access later on. Someone told me I should cover it with concrete to keep the bugs and vermin out of the house.

Here is a picture of the hole.

[i93.photobucket.com]

The most direct route for the tub drain would be to go left with a p-trap and wye into the main drain. Instead, the tub drain turns right with a p-trap (opposite to the flow of the main drain) and then heads away from the main drain. You can see the 3" pvc main drain running right to left in the bottom of photo. As I have sketched with dashed lines, the tub drain must turn back around and wye into the main drain. Again, drain works fine, just wondering why someone would do this.

Is there a vent for the tub trap in that back wall ? The trap needs a vent before it ties into the main drain .

A lot of houses that were built with lead or cast drum traps in an area that I used to do a lot of work in, and a development of slab houses built after WWII all had the tubs running into the stool hub or into a T just past the 90 on the bend of the toilet; I can see that as being more likely than running in a big loop. I would guess that they pick up the lavatory drain under the floor before the stool hub as well and use the lavatory drain as a wet vent for the bathtub.

That's a great point. I don't see a vent between the trap and main drain. It's hard to measure, but I think the trap arm and the main drain are at the same elevation....about 10 inches below the top of the concrete floor.

The main drain runs parallel and underneath the wall that separates the two back-to-back restrooms. This wall has been removed so I can see the main stack from floor to ceiling. If the trap arm connects to the main stack it must do so under or within the concrete floor. The main stack vent is about 42 inches away from the tub trap.

The house was built in 1985.



Edited 1 times.

possibly the "Y" was roughed in for a shower before the cement was poured and after they changed their mind and used a tub???

Unless we could see the entire drain line, anything we say would be a guess, just as your drawing is a guess based on what you CAN see.