View Full Version : converting from 1.5" to 2"

03-02-2007, 08:30 AM
New to the post and like what I see. I wish I would have found this place 2 years ago! It would have saved me money and many headaches!

I am elbow deep into a total remodel of a master bath. It is an older home (1947). I am re-tiling the shower and have EVERYTHING ripped out down to the studs and subfloor. Additionally, it is over a garage so I have complete access to everything above grade.

The shower drain I will install is standard 2" PVC. Typical 3 piece design for use with mortar bed showers. However, the old drain and pipes back to the wye are 1.5" galvanized and it is really quite corroded inside and was used rarely for the past decade because of massive leakage (shower pan, not the pipes). I have the opportunity to replace everything right back to the stack. I plan on keeping this house for another 30 years+ and am approaching everything else about this project with that mindset.

So, 2 questions on this:

1. is it worth it? Someone told me that the 1.5" to 2" is a big difference. That person also told me that not replacing galvanized might leave me open for future problems. I would replace with PVC.

2. The wye on the stack is actually a 2" wye (iron) with a 1.5" pipe inserted into it somehow. Everything here is sound and has some sort of collar? Or perhaps it is solder? Can I somehow remove the 1.5" pipe from the wye and place a 2" PVC pipe inside? If so, how? Grinder or sawzaw? I would prefer this method since it would be difficult to support the stack where I need to cut. Or will I have to cut out the wye and replace with a PVC wye and 2" drain pipe?

This is a 3" auxiliary stack that appears to be Iron. The main stack is larger than 3" but a good distance away.

Any and all help is appreciated.

03-02-2007, 12:28 PM
Any photos would be appreciated...
Look to see what kind of joints the main stack has...
Lead and oakum probably...
Also see what size is written on the wye...
If it is lead and oakum and the wye is a 3 X 2 fitting, should be fairly easy...
We can help much more with pictures...

03-02-2007, 12:30 PM
I will take some photos tonight. I also am going to try and see if the joint is lead solder or not by putting a torch to it.

03-02-2007, 02:05 PM
You'd need a monster torch to actually melt lead in a large joint, and you might just burn something down! At that size, it may be a threaded joint.

If you are lucky, the joint is 2". If not, then I'd rent a snap cutter, cut out a section (it is VERY IMPORTANT to support the run above - it can be VERY HEAVY) and install a pvc wye installing it with banded couplings - very quick and easy.

03-02-2007, 02:09 PM
1. is it worth it?

Yes. Definitely replace that galvanized with 2" PVC all the way to the larger pipe, and be thoughtful of trap placement and any venting that might be necessary.

Gary Swart
03-02-2007, 02:16 PM
Here's the math on the difference between 1-1/2" pipe and 2" pipe. Final figures are rounded off. This is just the old formula for the area of a circle, Pi times radius squared. For 1.5" pipe, the radius is .75" which squared = .5625. That figure times 3.14 (Pi) = 1.77 square inches. When the formula is applied to 2" pipe, the radius is 1" which squared = 1. That times Pi - 3.14 square inches. So you can see that a 2" pipe is just slightly less than twice as much area as a 1-1/2" pipe. This is why for draining large volumes of water quickly, the 2" is preferred. I trust you know you never reduce the size of a drain, it must stay the same size or larger.

03-02-2007, 07:33 PM
Thanks guys, great info... especially the math refresher. Cool to see those old formulas put to practical use...

I got crazy with the torch tonight and got the 1.5" pipe out at the stack. I am fortunate because my house is brick on block, so no worries about burning it down since the nearest piece of wood was over 2 feet above me. the pipe was 3x2 with lots of lead, oakem and fumes!

So, what about venting. originally, about 2 feet down the drain, there was a split and a parallel piece that runs about another 5 feet under the floor and then ties into the other vent system. it is still there and I would prefer not to touch that. Will that work? Is this what they call a "wet vent" system?

Also, now that the 2" cast iron wye is clear of pipe and solder... do I need to clean it out with anything special? Once that is done, how do I join the new 2" PVC drain I intend to install?

Thanks again for your help. I am clueless with plumbing. just ask my wife (as she chuckles next to me).

having issues loading the pictures... Sorry. Will try again when I am less tired!

03-02-2007, 08:41 PM
2 inch is the min required drain for a shower in MA.

03-03-2007, 05:45 AM
I got crazy with the torch tonight and got the 1.5" pipe out at the stack ...

So, what about venting.

First, did you temporarily stuff a rag or something into the wye to hold back any sewage odor?

Second, how far is the wye from your new shower drain?

03-03-2007, 06:12 AM
You will have to run a vent for the shower - the stack cannot serve as the shower's vent...
Important at this point...
Can you draw a quick floor plan with dimensions showing shower, stack location doors etc...?
Is there an attic above the bath?

03-03-2007, 07:05 AM
If the tub was vented then using that same opening for the shower will mean that it is vented also. Although if you are connecting to a "Y" in a vertical pipe, the old connection may not have been vented, and/or it was an illegal 3/4 "S" trap.

03-03-2007, 02:19 PM
It is an older home (1947). I am re-tiling the shower ...
The shower drain I will install is standard 2" PVC ...
... the old drain and pipes back to the wye are 1.5" galvanized ...

The initial drain issue here is simply that of switching from 1-1/2" galvanized to 2" PVC, and my own suspicion is that there is/was no accompanying "vent" in the original plumbing, and that there is no true, practical, functional reason or need to install one now unless there had already been problems at the trap prior to upgrading to 2". If the run is a short one, and maybe even if not, there is no way the trap would be sucked dry by the drain flow of a shower. But, it would also be helpful here to know a little more about the plumbing of and/or around that wye ...

03-04-2007, 01:33 PM
Ok... So to answer some of the questions...

1. I did stuff a rag in the Wye to prevent sewer gases.

2. the shower drain is 10 feet from the y with a 90 degree turn at 8ft.

3. in the old system, 2.5 feet after the trap there was a T with the drain contining straight through. the other pipe makes a 90 degree turn and runs back "uphill" to tie into the sink's vent and eventually into the stack. This too is about 10 feet away with about 4 feet of it running with barely any upward slope.

4. I have access to the the entire stack, from the garage at the bottom to the roof, which form the ceiling of this bath... As I said before, I have nothing but exposed studs and joists right now.

So, again... how does one properly go about inserting a 2" PVC into a 2" cast iron wye and will I need to run a seperate vent for the tiled in, no tub style, mortar base shower?

Sorry, but I cannot seem to draw or insert anything this weekend. I will tell you that the bath is a 4x9 bath with 4x4 of the left to be covered by the shower. and the right has a toilet and sink against the wall. Door is just right of center on the bottom and window is right of center on the top. Stack is in the top right corner and joists run left to right. Make sense? Simple set up.

Thanks again for all the help. (sorry, still can't figure out how to post pictures on this site.)

03-04-2007, 04:50 PM
If the previous drain/vent setup was working fine, I would guess you would be okay simply duplicating it.

Personally, I do not know how the pros would connect the new pipe to the wye, but surely it can be done!

How loose or tight is a piece of the new pipe in that fitting, and how large is the outside of that hub on the wye?

There are various bushings and couplings available, and you might have to look and ask around a bit to find the best one to use.

03-04-2007, 05:10 PM
If it is a 2" branch at the wye then they do make "donuts" to join the 2" PVC into the CI hub...
I think Fernco makes a few...

As for the drain...
running 8' then using a sweep (90 degree long radius elbow) and then another 2' to the t-wye for the P-Trap and vent will work as long as you still maintain the vent connection to the lav... (has to attach at least 6" above the flood rim of the lav...)
Sounds like you had a vented shower before - should just be able to duplicate it...
Just make sure you use all drainage fittings under the flood rim of the shower...

03-05-2007, 05:37 AM
Thanks leejosepho and markts30 for the comments.

Markts30, I think I found the donut that you spoke of. It is made by Fernco. I will let you know how it works. Also thanks for the tip on drainage fittings. I made sure to get drainage, not the other "straight" kind.

So I plan on duplicating what was already there. Hopefully this will go better than most of my plumbing experiences!

You guys might make a plumber out of me yet! Thanks again!