Is this the correct plumbing for a vanity drain?

[Mini Me]

Here is what I have.
I know that I need a transition between the 1 1/4" OD grey plastic pipe and the 1 /12" ID ABS pipe (see the third picture)
One of these :

The rough in for the drain is just a 90 elbow installed horizontally (female female) like below -see the new sink plumbing; the rendering shows the idea of how the sink is vented and how that elbow, that is now out of the wall with one end, was installed.;

The intended plumbing under the sink looks like this

The part that I do not understand or I do not know is why is the last to the left slip nut in the below picture needed?
I am seeing that in lots of pictures on internet

 

[Reach4]

I would not use that intended glued trap under your lavatory. Slip joint (SJ) is the good way for easy adjustability and cleaning.

The part that I do not understand or I do not know is why is the last to the left slip nut in the below picture needed?
I am seeing that in lots of pictures on internet

Attaches the trap arm to the trap adapter, plus keeps the washer in place and compressed against the p-trap arm.

That trap adapter in your first picture has such a nut. You can mix slip white and black. You can also find p-traps in black as well as white.

 

[Sponsor]

 

[wwhitney]

Aside: in your DWV rendering, just to clarify, the bottommost green fitting is actually a LT90, not some sort of tee as it is rendered?

As to your question, there's tubular pipe and Schedule 40 pipe. Tubular pipe is called by it's actual OD, 1-1/4" or 1-1/2". Schedule 40 is called by its nominal ID. Tubular pipe is joined with slip joints (nuts and compression washers), and plastic Schedule 40 is typically glue joint. The trap adapter (your first photo) glues onto Schedule 40 pipe (or into a hub) and provides a slip joint connection for tubular. A 1-1/2" slip joint connection can receive a 1-1/4" tubular pipe using a reducing washer, so I prefer to use a 1-1/2" trap adapter in all cases to preserve future flexibility.

So you have 1-1/4" tubular at the sink tailpiece, and 1-1/2" Schedule 40 at the wall. Your trap could could be 1-1/4" tubular, 1-1/2" tubular, or 1-1/2" Schedule 40. Your last picture show a tubular trap, and to use it the trap adapter would be at the wall. The leftmost SJ nut in the picture is actually part of the trap adapter. Your second to last picture shows a Schedule 40 trap. The trap adapter would be on the sink tailpiece; the trap has a union connection, so that the trap and Schedule 40 tailpiece could be removed by undoing the trap union and the trap adapter nut.

I generally favor tubular traps, with the trap adapter at the wall. I'm not sure what the upside to using a Schedule 40 trap would be.

Cheers, Wayne

 

[Mini Me]

Aside: in your DWV rendering, just to clarify, the bottommost green fitting is actually a LT90, not some sort of tee as it is rendered?

good catch, yes that is an error it is a 90 there as we discussed a while ago

 

[Mini Me]

Since I already have the ABS black fittings (from what I read you call them schedule 40) I would prefer to use a trap adapter like in the first picture
This will be installed between the sink tail piece and the vertical of the P trap as in my third picture

Where I have a big question mark is at the end of the horizontal arm of the P trap
I currently have that 90 elbow installed as in the rendering and I need to know if I can/should glue it to the horizontal arm or I should find a way to use a slip nut join there (and what are the fittings to do the transition)
Another option could be to glue a small piece of 1 1/2" pipe to the 90 in the wall and then I could use a rubber connector to connect 1 1/2" ABS to 1/2" ABS.

Here is the picture of my rough in

 

[Bannerman]

Tubular 1.25" chrome traps are available for exposed installations such as a wall hung or pedestal sink, but for in-cabinet installations, the transition from a 1.25" tailpiece to 1.5" ABS is commonly performed above the trap using a 1.25 X 1.5 trap adaptor as shown in the initial image.

Using a trap with a union fitting as shown in the 3rd image along with the trap adaptor, will allow the section between the sink tailpeice to the union to be easily removed if there is ever a large blockage within the trap that cannot be removed through the trap cleanout, and if required, will allow easier access to snake out the line after the trap.

As a further aside, your 2nd image suggests the distance between the new trap and the vertical stack may exceed the allowable horizontal venting distance. If so, you will likely need to incorporate an air vent closer to the new trap so as to prevent water from being syphoned from the trap.

 

[Reach4]

This will be installed between the sink tail piece and the vertical of the P trap as in my third picture

You will have to glue perfectly to avoid mis-alignment.

 

[Mini Me]

Using a trap with a union fitting as shown in the 3rd image along with the trap adaptor, will allow the section between the sink tailpeice to the union to be easily removed if there is ever a large blockage within the trap that cannot be removed through the trap cleanout, and if required, will allow easier access to snake out the line after the trap.

yes that part of the setup is clear
what I do not know is if I need to install a slip nut join at the wall end of the horizontal arm of the trap

As a further aside, your 2nd image suggests the distance between the new trap and the vertical stack may exceed the allowable horizontal venting distance. If so, you will likely need to incorporate an air vent closer to the new trap so as to prevent water from being syphoned from the trap.

That design was discussed with @wwhitney a while ago. The horizontal distance is 24" (1/2 of the width of the vanity cabinet) +16" (1/2 of the width of the shower base) The vanity is within 1/4" distance the edge of the shower base, it is(will be) very tight and probably 1/2"-1" distance from the shower glass panel that will be installed on that edge.
I think this is covered and ok. Worst case scenario I will open the wall from the other side and add the vent

 

[Mini Me]

You will have to glue perfectly to avoid mis-alignment.

I will position the p-trap first and connect it to the sink tail and after that I would implement whatever I would be advised here for the end of the horizontal arm of the P trap
that is where my problem is
Do I need to add more fittings to be able to install a slip nut joint between the rough in and the horizontal arm ?

 

[Bannerman]

what I do not know is if I need to install a slip nut join at the wall end of the horizontal arm of the trap

In this situation, because you are transitioning from the 1.25" tailpeice to 1.5" ABS above the P-trap, a threaded fitting at the wall will be unnecessary and an additional potential location for leakage.

If you do want the trap arm to be removable, suggest not using a slip joint fitting but instead using 1 each of the fitting examples linked below.

1-1/2 in. ABS DWV Hub x MIP Adapter
1-1/2 in. ABS DWV Hub x FIPT Adapter

 

[Mini Me]

In this situation, because you are transitioning from the 1.25" tailpeice to 1.5" ABS above the P-trap, a threaded fitting at the wall will be unnecessary and an additional potential location for leakage.

If you do want the trap arm to be removable, suggest not using a slip joint fitting but instead using 1 each of the fitting examples linked below.

1-1/2 in. ABS DWV Hub x MIP Adapter
1-1/2 in. ABS DWV Hub x FIPT Adapter

Agree with the aditional leakage point that is why I built what you see in the third picture. I just wanted to make sure I am not missing any other reason whythat slip nuts shows in so many other pictures. Thanks a lot everybody

 

[wwhitney]

I currently have that 90 elbow installed as in the rendering and I need to know if I can/should glue it to the horizontal arm or I should find a way to use a slip nut join there (and what are the fittings to do the transition)

Just to more explicitly reiterate what I and others have mentioned, SJ connections are not used with Schedule 40. And it would be very weird to transition more than once between tubular and Schedule 40. So everything downstream of the trap adapter is Schedule 40, typically glue joint. And everything upstream of the trap adapter is tubular.

Cheers, Wayne

 

[wwhitney]

Tubular 1.25" chrome traps are available for exposed installations such as a wall hung or pedestal sink, but for in-cabinet installations, the transition from a 1.25" tailpiece to 1.5" ABS is commonly performed above the trap using a 1.25 X 1.5 trap adaptor as shown in the initial image.

So is that a common practice in Canada, to use a Schedule 40 trap? What's the upside over a SJ tubular polypropylene trap?

Cheers, Wayne

 

[Mini Me]

So is that a common practice in Canada, to use a Schedule 40 trap? What's the upside over a SJ tubular polypropylene trap?

Cheers, Wayne

Probably...they are all like that in my house

 

[Bannerman]

ABS continues to be the DWV material most commonly utilized for above grade whereas PVC is utilized below grade.

Common practice to use ABS within a cabinet? Yes.

Benefit over a tubular polypropylene trap? Probably none except the example shown above appears to be a 1.25" drain assembly, thereby locating the transition from 1.25 tubular to 1.5" ABS at the wall where a leak may not be noticed for some time.

When the drain assembly is exposed and a 1.25" chrome to SJ transition to 1.5" ABS must be made at the wall, a deep escutcheon cover will be utilized to hide the SJ fitting. Example shown here: Adjustable Chrome P-Trap Drain