How sensitive are tub drain kits to output placement?

[Dgeist]

I recently had my basement slab stubbed out for a 3-fixture bath. I had marked 16" out from the back wall for the centerline of the tub since I'm getting a 32" tub (toto cast iron soaker).

My city inspector wanted the tub drain wet vented by an adjacent lavatory, thus the plumber had to build out a trap about 10 inches down from the slab top and a 1.5" riser to the tub drain location. I would have expected a horizontal stub into the concrete "box" and a connection type similar to a sink drain, but I'm trusting that what my plumber did is at least kosher with respect to code.

Do modern drain kits have enough "swing" for output stub placement that's not close to perfect (i.e. if the drain line is 1" off center and 1/2" too far out from the wall)? The work hasn't been inspected or closed up yet, so if this needs changing, I want to let my plumber know now.

Thanks.
Dan

 

[hj]

In the first place the drain for a 32" tub is usually not 16" and while the drain is "adjustable", using more fittings, whether it will do what you want it to depends entirely upon where it is now, compared to where you want it to be. If that black box is a backwater valve and that pipe to the left coming down from upstairs is a drain, the BWV is in the wrong spot. Whoever installed the piping sure liked to use a lot of unnecessary fittings. Maybe he wanted to get rid of all his extra stock. I don't know what that third pipe is to the right fo the toilet connection, but it may have been unnecessary.

 

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[Dgeist]

Hi, HJ. Thanks for the response, and all of your concerns are things that have been discussed.

The box in indeed a backwater valve. My county requires that any fixture group below the first manhole serving the line outside the home be protected by a backflow prevention device. These are the only fixtures in the basement with the exception of a 2" trap with standpipe just out of frame to the top left. We went back and forth with whether to install the valve on the new branch of the main drain and ended up with where it is since it would protect both the bathroom group AND the small standpipe for the water heater and furnace condensate and Pressure relief valve. Had we not needed that standpipe, the valve would have been put at the base of the branch serving the bathroom group. The sewer has backed up into the house previously, so the concern here is mostly preventing that. I understand that a clog upstream of the valve might still result in an overflow inside the home, but that would be the case regardless of which location it's in.

I wanted to put the standpipe off the branch and dry-vent it up through the future wall instead of cut into the vertical 4" but apparently the city also doesn't like dry vents anymore (no idea why) but was okay with having a stack vent serving a 2" trap and standpipe. Can you think of a better way to do it?

As for the "extra fittings", our original design called for a simple straight trunk with wyes to the left and right to pick up the WC and tub then wet vent them both with a the lav drain riser in the wall. There is also a bar sink planned for the other side of the wall and the city would not allow the bar sink to be part of the bathroom group, thus we were forced to have it drain to the 3" branch downstream of the bathroom group.

It's interesting that you say a 32" tub doesn't have a 16" drain centerline since the spec sheet says exactly that...

Dan

 

[hj]

IT must be a "plastic" tub then because most tubs have wide apron on the front and the drain is centerded on the actual "tub" width.

 

[Dgeist]

32" is the tub width... was I not clear on that? It's a cast iron Toto, 64-3/4 x 32 x 16-3/4

 

[hj]

The "tub" width I am referring to is the actual width of the opening where the water goes. Usually it is NOT symetrical with the overall width and the drain is in the center of it. In your case it is symetrical, since the rear edge appears to duplicate the front, which is unusual.