Tying in new shower drain to tub drain

[Derek K]

Hi all,

Many time reader of this forum, but am really hung up on tying my shower into existing drain for sunken tub. I have a 2" vertical stack, going into a 3" at basement floor level with a cleanout. The existing tub had a 5' long 1 1/2" drain line with a vent about in the middle before dropping into the drain pipe with a 90* elbow.

My new shower drain is about 16" from the vertical stack, which I swapped out the 90* top for a double sani-T, since I have a cleanout just 6' below the T. The issue is, the P trap outlet bottom (with the bottom of it aligned with the bottom of the floor joist) is ~4.5" from the bottom of the floor joist. The Sani-T inlet is 2.75" from the bottom of the floor joist, and I only have about 16" of run to drop 1.75" of height.

How can I best drop the 1.75" vertically in 16" run? I was considering doing 2 22.5*fittings to get to the right height.

 

[IPDQKWID]

I think the trigonometry makes a 22.5 too far of a drop (more like 4+ inches over 16" run). Trying to make it fit will probably put too much strain on the 22.5 joints
What if you cut the stack just above the San-T and glue a new san-T and a short length of pipe with coupler to the existing stack, putting it at the proper height?
When you say double san-T, you don't mean there's another horizontal inlet for something else, do you? A regular san-T I think inlets higher than a true double san-T, which would save you the space you would need to get the fitting at the right height.

 

[Sponsor]

 

[IPDQKWID]

I think I just realized the double san-T. The other inlet receives the tub drain. So I suppose the drain slant doesn't allow you to easily change the height of the san-T. Maybe a combination wye- 1/8 bend gets that drain pipe to the right height?

Basically, the tub and shower drains come into the stack at different heights? I don't do this for a living (at all), but maybe this pic shows what I'm thinking?

 

[Jadnashua]

FWIW, you cannot exceed 1/4" per foot on your trap arm before the line is vented.

If you're replacing a tub with a shower, the inspector would want that line to be 2" to meet current codes. They MIGHT allow you to keep an existing 1.5", depending on how flexible they are and how difficult it would be to change things out. Some are somewhat reasonable, but they are supposed to require remodeling to come up to current standards.

 

[Derek K]

with the double sani-T, both of the drains come in on opposite sides at the same height. With the short 16" run to drain and the 1.75" drop being less than the ID of the Shower drain (2"), I thought I would be able to do a combination of 1/4" per foot and some shallow angles to get to the desired height and still have the vent "see" the trap.

 

[Terry]

You can't use a combo on the vertical for a trap arm, or a wye with 45 or any fittings that raise the trap arm.

You can use a santee.

 

[Derek K]

Thanks Terry