How do I add a horizontal drain in a wall when the framing is done ?

[Mini Me]

Hi guys


I have been designing the heck out of this but I never considered this issue. In the below picture I need to add 1.5" ABS pipe to build a drain and a dry vent (the green horizontal segments) What is the usual practice for this? How does one install the pipe when the studs are in place and moreover the wall to the left has cabinets on the other side )? (the studs are 16" apart)
Just to be clear both walls have the framing competed there is no open end for the wall where the sink will be located. For the other wall I can probably drill a hole in the stud that is at the right as that side is facing an open space but it might not be long enough (not as long as the pipe segment that I want in there.

Do I have to use small segments and couplers ?

 

[wwhitney]

Why is the stud just to the right of the sink lav doubled? Is the wall load bearing?

How do you feel about furring out the wall 1-1/2" and notching the studs 1/2"? If it's not load bearing, you could notch the studs 1-1/4" and fir them out only 3/4".

I think PVC is more flexible than ABS. If you moderately oversized one hole in one stud in each horizontal run, I bet you could get half-length pieces in there so you only need one coupler on each horizontal. Not sure if you could do the same with ABS.

Another possible strategy is to heavily notch one stud and put in a loose (not too loose) full length stud in an adjacent stud bay against the adjacent stud. Then you can run your pipes taking advantage of the heavy notches, and finally slide the loose stud over against the notched stud to sister it as a repair. Your loose stud would need holes that are a bit over 1/4" taller than normal (racetrack shaped), so that you could slide it 13" while accommodating the slope of the pipes.

Cheers, Wayne

 

[Sponsor]

 

[Breplum]

Great drawing btw !!!
As you are imagining, yes, either we would have to drill an extra hole to feed a longer piece or smaller segments and couplings.
If space allows and plastic pipe is used, we often feed longer segments from inside and shove the bowed pipe in. Helps to have two people and use a block of wood and maul to drive it while overcoming friction.

 

[Mini Me]

Re drawings thank you!..please see my other posts about this project I have the entire house in Sketchup and I keep adding details

Trying to answer all the questions asked above
- the wall where the sink is has cabinets on the other side so notching could make the wall fail as I would need to notch at least two or three studs at the same time, put the pipe in and then patch it back by furrying, sistering etc etc
-the doubled or tripled studs are there because there was a wall there creating an alcove for a bathtub that was there
-I can't explain the second set of tripled studs (there is a stove and a hood on the other side and I guess they might have needed wood to anchor is
The guys who worked this basement must be put in jail, I am quite sure this is not the ex-home owner who cut so many corners and did so much corner cutting here

The dry vents could be stepped downward with each space between studs but it would be weird
I am inclined to use couplers ...is that a code compliant solution for situations like this?

 

[Reach4]

Why is the stud just to the right of the sink lav doubled? Is the wall load bearing?

How about moving the trap adapter a foot to the right? Maybe come out of the wall at 45 degrees, and avoid cutting those structural pieces two places.

 

[Mini Me]

How about moving the trap adapter a foot to the right? Maybe come out of the wall at 45 degrees, and avoid cutting those structural pieces two places.

It will hit the opening cut by the manufacturer in the drawer see this https://www.baindepot.com/media/ftpbaindepot/pdf/19-VW1205CEM.pdf

 

[Mini Me]

So I ended up implementing the below
I am questioning the need to have the purple segment
The green blue selected segment is already in place, the green segment between the shower vent and the sink is what I am building (still dry fitting the pieces but I did not drill the holes for the studs to the left of the vertical green segment
The distance between the two green verticals is 4'

I am also considering an air admittance valve

 

[Reach4]

So I ended up implementing the below
I am questioning the need to have the purple segment

Really? Sorry to hear that. It's not right from a functional view as well as a code view.

What you should have done is to not have a santee on the left, but instead run the trap into a long or medium elbow in the horizontal plane. If you did that, then the allowable distance to the vent determines if you need a vent before the santee on the right.

But this doesn't keep you from putting the penetrations into your supports. It just reduces it from two pipes to one.

I am also considering an air admittance valve

If Toronto allowed AAVs, that would work.

 

[wwhitney]

What's the height above the floor of the horizontal green pipe you've run? [And how did you end up running it?]

With a sanitary tee in the wall, the top of the sanitary tee is your vent take off. In which case you either need to stick with your original plan, or put an AAV in the wall (if allowed by Canadian plumbing code, I'm not familiar with it and don't know where to find it.)

If you can lower the trap so the outlet is the same height as your horizontal green pipe, then you could just put a horizontal elbow in. In that case the purple pipe is potentially useful. Your horizontal trap arm would require a vent take-off within a prescribed distance (varies by code), and if the vertical pipe on the right is farther than allowed, the purple pipe would provide the vent takeoff within the prescribed distance.

If you are allowed to use AAVs, you could also put one inside your lavatory vanity cabinet. In which case you wouldn't have to lower the trap, and you could replace the sanitary tee with an elbow.

Cheers, Wayne

 

[Mini Me]

I am reading that

trap arm size trap max developed length @ 1/4"-per-foot slope
1 1/4" 5 feet
1 1/2" 6 feet
2" 8 feet

Consistent with this
https://inspectapedia.com/plumbing/Plumbing-Vent-Distance-Codes.php

I do not care about regional codes, sorry. As far as I am concern the Physics is what it matters to me
yes AAV is allowed in Ontario

http://www.buildingcode.online/1106.html

if I read the below correct I should be OK with an AAV

THE ONTARIO BUILDING CODE | AIR ADMITTANCE VALVES


7.5.9.2. Air Admittance Valves

(1) Air admittance valves shall only be used to vent,

(a) fixtures inbuildings undergoing renovation, and

(b) installations where connection to a vent may not be practical.

(2) The air admittance valves shall be located,

(a) above the flood level rim of the fixture it serves,

(b) within the maximum developed length permitted for the vent,

(c) not less than 150 mm above insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation materials, and

(d) installed in a location not subject to back pressure.

(3) Air admittance valves shall,

(a) only vent fixtureslocated on the same storey, and

(b) be connected to the horizontal fixture drain.

 

[Mini Me]

Really? Sorry to hear that. It's not right from a functional view as well as a code view.

What you should have done is to not have a santee on the left, but instead run the trap into a long or medium elbow in the horizontal plane. If you did that, then the allowable distance to the vent determines if you need a vent before the santee on the right.

But this doesn't keep you from putting the penetrations into your supports. It just reduces it from two pipes to one.


If Toronto allowed AAVs, that would work.

that part is not implemented, only the green segments that have a blue contour (that means selected in the Sketchup program)
so practically I could still run the horizontal elbow out of the trap arm but I tought that placing that pipe as low as possible will avoid punctures from ppl drilling the walls later

I also have this problem with supporting the shower glass panel using a 2x6 or 2x8 which I need to pre-install
but if you have an 1.5" pipe in that wall going horizontal then you still need to guess where the clamps are positioned since
there will be segment where the pipe is where you can't really install the 2x6 or the 2x8
see the picture below

so the question is is the clamp distance to ground adjustable or it is something that is fixed depending on model and predrilled holes in the glass (specific to each manufacturer)

 

[wwhitney]

trap arm size trap max developed length @ 1/4"-per-foot slope
1 1/4" 5 feet
1 1/2" 6 feet
2" 8 feet

Those are the theoretical maximums based on 1/4" per foot and the trap weir rule (the vent takeoff (the opening at the top of the pipe for the vent) can't be below the trap weir (the bottom of pipe at the horizontal trap exit), because then the pipe could fill with water and siphon the trap). But you can only achieve them when doing a vent takeoff with a combo (a san-tee has a little extra drop before the vent takeoff), and only if your trap arm is at exactly 1/4" per foot. So some codes have a shorter maximum.

What's your stud spacing? If it's 16" o.c. your trap arm would be just over 4' (but then your shower enclosure would only be 30" wide). In this case, as long as you get your trap arm at exactly 1/4" per foot, you could have the trap arm enter the wall with an elbow and run horizontally to the right to a san-tee. Less drilling of studs.

But if your stud spacing is 24" o.c., your trap arm would be over 6', too long for the option of running over to a san-tee in the right most stud bay for your vent. You could still put a vent take-off in the second stud bay, that way you'd only have to drill one stud for the vent.

On the AAV information you posted, looks like under the sink is prohibited. So you'd have to add a vented recess wall box above the lavatory to hold your AAV. The main advantage of this route is that you don't have to fix your lav p-trap height ahead of time, you could run the horizontal lav drain lower in the wall and use a san-tee above it, and in the future you could more easily lower the lav p-trap if need be.

Cheers, Wayne

 

[Mini Me]

Re: how I installed the horizontal segment to the right-that one went in easily because I could cut a hole in the stud at the end (not seen in the picture) which was exposed . I also needed a T there to connect the drain for a condense furnace pump that comes from another room via ceiling. That segment is properly sloped (1/4" per foot)
Re: distance between studs - it is 16" oc
Re: going horizontal after the trap arm enters the wall -that is not possible because of the geometry of the vanity cabinet/shelves and because of the three freaking studs that were put there by the guys who built this.
Here is a sketch where I am explaining why I can't use a large or short 90 there. Basically the P trap will be confined in that space because of the cut of the drawer as seen in post #6 in this thread. I barely have room to direct the trap arm toward the left side of the studs. When it lands there I need to go down because a 90 won't work there (see the cross cut section below) hence the solution shown in my above diagrams (go down and then install a 90 there in the vertical plane not in the horizontal. I guess my only solution here is to vent from above as initially planned or install a AVV as I will depict in the next post in this thread

 

[Mini Me]

Since the AAV is not allowed under the sink I could extend the vertical for the drain up to the framing box created on the other side of the wall for the hood of the electric range that I have on the other side of the wall and install the AAV there but it is less accessible. This is not air tight (see the figure below)

the other place for it would be behind the things I have on the wall above the sink (mirror or shelf) I can create a niche there and make sure it is not air tight

 

[wwhitney]

So why are there double studs there?

And if I understand correctly, the problem with a horizontal 90 is that it would still be bending after it exits the wall, and the result would impinge on the narrow channel in one of the drawers? There's not a height you can put it at where it would be between drawers? You could modify the drawer.

Cheers, Wayne

 

[Mini Me]

So why are there double studs there?

And if I understand correctly, the problem with a horizontal 90 is that it would still be bending after it exits the wall, and the result would impinge on the narrow channel in one of the drawers? There's not a height you can put it at where it would be between drawers? You could modify the drawer.

Cheers, Wayne

re: studs-I suspect it was patch work and there was also a wall perpedicular on the two studs you see there to the left (to create an alcove for the bath tub that was along that wall)
re: modifying the drawers: too much work considering that the AAV solution is so simple
re: horizontal 90... it will need bending in order to get back to there the P -trap is
a solution would be to direct the P trap toward the 90 but it will require one more 45 if that is even possible

 

[wwhitney]

re: horizontal 90... it will need bending in order to get back to there the P -trap is

Presumably the bending you mention is based on the idea of a simple hole through the double studs, which requires the 90 to be all or mostly to the left of the double studs. But if you notched the double studs, you could put the 90 where the sink plumbing wants it to be.

Hence my question of what the double studs are doing. If they are there for no particular reason (seems implausible), notching them ought to be OK. But if they are carrying a big vertical load from above, then it requires some thought to be sure drilling them is OK, and notching is off the table.

The old perpendicular wall you mentioned, it was lined up so its stud against the remaining wall spanned from about the middle of the left stud in the double to about the middle of the stud next to the double stud? If so, that would explain the left hand stud of the double (drywall backing), and if the double is joined to the stud to the right by some intermittent blocking or spacers, that would explain the whole double stud. And if that's the only reason it's there, would mean it's plausible to notch it.

But that still leaves the question of why there's another double stud at the far left.

Cheers, Wayne

 

[Mini Me]

Used to be like this

 

[wwhitney]

Hmm, that layout doesn't really explain the double or triple studs. What's above them?

Cheers, Wayne

 

[Mini Me]

not a bearing wall
the bearing walls are marked with red here (cinder block walls)