Want to move 3.5" vent pipe in a 2x4 wall

[zver11]

I would like to put in a in-the-wall medicine cabinet over a bathroom sink. A 3.5" OD PVC vent pipe rises through the center of the 2x4 wall behind the sink. Believe it vents multiple bathrooms. This bathroom is on top floor with a very short distance ceiling to roof.

Problem is how do I put in elbows when the pipe is the full thickness of the wall cavity? I expected to use 45 degree elbows to route around the new medicine cabinet space and back to meet the existing pipe at the ceiling. I could surface mount if I had to, but prefer a recessed medicine cabinet.

 

[Reach4]

2 narrow recessed medicine cabinets, and a mirror between.

Have the hinge on the left for the right cabinet, and the hinge on the right for the left cabinet. That way the mirrors can work together to get multiple viewing angles.

 

[Sponsor]

 

[zver11]

Difficult to implement well in my situation. 36" cabinet in corner with outside wall.
Anything wrong with the following:
sched 40 Insert-insert couplings join sched 40 pipe to sched30 pipe and build detour with 45 degree elbows and pipe made with sched 30 PVC. Also considered using a lot of insert connectors and all sched 40 parts except street-street elbows are hard to find--. Am I correct that a sched40 insert connector can be used to connect to sched 30 pipe? I believe the two have same ID and both compatible with same PVC cement

 

[Reach4]

Difficult to implement well in my situation. 36" cabinet in corner with outside wall.

I suspect you could find a way, to fit a mirror and a bit of storage in your space while leaving the vent pipe intact. I am not sure I am picturing the space correctly, but that does not matter.

Insert-insert couplings

The term Insert couplings is usually used to describe barbed fittings used for polythene pipe etc. https://pvcfittingsdirect.com/pvc-insert-fittings-1/

Do you mean ordinary slip fit glued couplings? A 2x4 wall has 3.5 inches of space if you are lucky. 3 inch PVC, schedule 40, and schedule 30 is 3.5 OD. The couplings would add maybe another 1/2 inch?

https://www.pvcfittingsonline.com/3-schedule-40-pvc-pipe-extender-s0301-30.html may be similar to what you are thinking about, except I don't think you would find those in elbows.


Do you really need a 3 inch PVC vent? Would 2 inch be enough?

Two 2 inch pipes in parallel would have almost as much area as a 3 inch pipe.

 

[Michael Young]

can you just jog around it with four forty-fives

 

[zver11]

I suspect you could find a way, to fit a mirror and a bit of storage in your space while leaving the vent pipe intact. I am not sure I am picturing the space correctly, but that does not matter.


The term Insert couplings is usually used to describe barbed fittings used for polythene pipe etc. https://pvcfittingsdirect.com/pvc-insert-fittings-1/

Do you mean ordinary slip fit glued couplings? A 2x4 wall has 3.5 inches of space if you are lucky. 3 inch PVC, schedule 40, and schedule 30 is 3.5 OD. The couplings would add maybe another 1/2 inch?

https://www.pvcfittingsonline.com/3-schedule-40-pvc-pipe-extender-s0301-30.html may be similar to what you are thinking about, except I don't think you would find those in elbows.


Do you really need a 3 inch PVC vent? Would 2 inch be enough?

Two 2 inch pipes in parallel would have almost as much area as a 3 inch pipe.

 

[zver11]

Issue with pipe diameter is that with a 3.5"OD pipe, a fitting that goes around the pipe will be to big for the 3.5" thickness of the wall cavity. The coupling I am proposing is an "internal spigot x internal spigot" fitting as described by plumbingsupply.com (sorry about imprecise description in prior post). This does not increase the diameter at the coupling location so that it fits within the wall.
My understanding is that Sched 40 pipe is 3.5"OD, 3" ID and sched 30 is 3.25"OD and 3"ID. Couplings for sched 30 are designed to fit in a 2x4 wall(3.5" cavity)

The alternative of two 2" pipes still needs a Tee or Wye that was 3.5" max OD to come off the existing 3" sched40 pipe.

 

[Reach4]

The coupling I am proposing is an "internal spigot x internal spigot" fitting as described by plumbingsupply.com (sorry about imprecise description in prior post). This does not increase the diameter at the coupling location so that it fits within the wall.

https://www.pvcfittingsonline.com/catalogsearch/result/?cat=0&q=internal+spigot+x+internal+spigot
None of those are elbows.

 

[jcy110]

Use 2 of these...... https://www.plumbingsupply.com/pvc.html#internalcoupling

Then heat a section of pipe by turning it over a barbecue grill sliding it back and forth. You can bend it to fit in the wall. DONT KINK IT. Make a form on plywood to hold it in place until it cools.

On small diameter you can tap the caps on and the heat creates pressure and you cannot kink the pipe. 3/4 or 1"..............3" might develop pressure.........and pop the cap on one end....

 

[Cacher_Chick]

It is pretty common to build the wall containing the primary waste and vent stack out of 2x6 framing, or a second row of 2x4's turned sideways.

Deending on what is on the floors above and below, it is also possible to reroute the stack entirely.

 

[Jadnashua]

WHat many places end up doing is furring out the wall with another set of 2x4's so there's enough room behind it to recess the cabinet. That's what I ended up doing on mine rather than trying to cut more holes in the studs and worrying about the thickness.

You could put a second layer of drywall up on that wall which would add just enough depth to accommodate the fittings, but the pipe is probably centered now, and you might need to do the same on the other wall behind it. You can buy 1/4" thick drywall and do it on both walls around the pipe.

 

[Reach4]

It is pretty common to build the wall containing the primary waste and vent stack out of 2x6 framing, or a second row of 2x4's turned sideways.

A 3.5" OD PVC vent pipe rises through the center of the 2x4 wall behind the sink.

Did you measure the wall cavity?

 

[FullySprinklered]

There actually is an inside the pipe fitting for 3 inch pvc. Had one arrive on the job two days after I didn't need it anymore. It was for the drain on a wall-hung Toto toilet. The decorator was in charge of ordering all the parts. Thanks, bitch.

Forty-five degree fittings? They don't work on a 3.5 wall either.

You can take a chisel and scoop out the gypsum on the inside of the sheetrock.

Takes gonads of iron, but it will work.

 

[Reach4]

Then heat a section of pipe by turning it over a barbecue grill sliding it back and forth. You can bend it to fit in the wall. DONT KINK IT. Make a form on plywood to hold it in place until it cools.

zver11, if you try that, take pictures!

Maybe some day some service will print out the special PVC pieces somebody wants on a 3D printer. I don't see that happening economically soon.

 

[Jadnashua]

I used a heat gun to bend a small pvc run for the condensate drain on my air handler. Not recommended, and it would be lots tougher on larger pipe...don't get it equally soft, it will stretch or kink or collapse. NOt recommended. This drain just ran outside, so I wasn't worried if it didn't work out. The variations in diameter would also make snaking it tough, too!

 

[Cacher_Chick]

If one is making an effort to comply with their applicable codes, they won't be fabricating any plumbing fittings or heating and bending PVC pipe.

 

[Michael Young]

If one is making an effort to comply with their applicable codes, they won't be fabricating any plumbing fittings or heating and bending PVC pipe.

Generally I would agree with you cacher-chick. But this is a homeowner working on his own home. And it's just a vent. It's not going to create a safety issue. So if they bend the pipe to cheat a bit, then friggin go for it.

 

[FullySprinklered]

If one is making an effort to comply with their applicable codes, they won't be fabricating any plumbing fittings or heating and bending PVC pipe.

screw the codes, we're having fun here

 

[Nakopf]

I suspect you could find a way, to fit a mirror and a bit of storage in your space while leaving the vent pipe intact. I am not sure I am picturing the space correctly, but that does not matter.


The term Insert couplings is usually used to describe barbed fittings used for polythene pipe etc. https://pvcfittingsdirect.com/pvc-insert-fittings-1/

Do you mean ordinary slip fit glued couplings? A 2x4 wall has 3.5 inches of space if you are lucky. 3 inch PVC, schedule 40, and schedule 30 is 3.5 OD. The couplings would add maybe another 1/2 inch?

https://www.pvcfittingsonline.com/3-schedule-40-pvc-pipe-extender-s0301-30.html may be similar to what you are thinking about, except I don't think you would find those in elbows.


Do you really need a 3 inch PVC vent? Would 2 inch be enough?

Two 2 inch pipes in parallel would have almost as much area as a 3 inch pipe.

I just pictured someone trying to run a cable with a 3" head from the roof vent and running into the twin 2" parallel vent modification.