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Thread: More tub to shower conversion

  1. #1

    Default More tub to shower conversion

    I'm remodelling my 1953 bathroom (found the original City of Phoenix inspection tag on the vent!), took out the tub and putting in a tile shower. I have plenty of tile, carpentry, and plumbing experience, etc., but putting it all together for the first time.

    It's slab on grade, so I had to saw, pound, and chisel out the slab to center the drain (much pain there... I don't think they make concrete like they used to!). Here I am, holiday visitors approaching, and I'm stuck at the drain. So, questions:

    1. I'm trying to get the 1-1/2" elbow out of the 2" trap so I can connect the new ABS drain. The galv elbow threads into a reducer that's leaded into the cast iron trap. Lots of propane did nothing. Sawzall did nothing. Gonna try drilling out lead and getting a stronger breaker bar to twist. Any other ideas?

    2. Since the cast iron is good, i'd like to run an ABS arm over from the shower train and drop into the trap. A (apprentice) plumber friend said that the 30" is too long of a "dirty arm", but I looked at the 2003 IPC, and it just says the trap shall be placed as "close as possible" to the fixture outlet... is 30" OK, or should I remove the whole trap and put in an ABS trap under the drain (very hard... more slab cutting!)

    3. Worse comes to worst, and I can't get the 1-1/2 elbow off, is there a good way to commit the cardinal sin and downsize? All of the shower drains I can find are 2", so I would have to bottleneck at some point.

    4. Most of what I've read on installing the membrane says it's to protect the subfloor. I have a concrete slab. Isn't the membrane less critical? Can I get away with laying the membrane flat on the floor? Can I avoid the membrane altogether? Who cares if water seeps into my slab?

    5. I hear a lot about this Kerdi stuff... is it really the cat's meow (as compared to mud & membrane)? What's the lead time to get it? Do any of the usual places (HD, Lowes, Ace, etc.) sell it?

    Thanks for any suggestions!

  2. #2


    I don't have much to offer here....but I've used a small chisel to remove the lead from that type of joint. It probably has oakum (rope looking stuff) packed under it which can be dug out if necessary. As for the liner...someone else can give a better answer...but you do want to seal up the the wall a little way. My first stupid tile job was a shower I built for myself and I thought I'd not have a problem since I had a concrete slab. It didn't take but a couple of days of use before I had water in the next room! I had to tear out the bottom of the shower and install a liner and completely re-do the tile floor and about 8" of the wall.... definitely an educational experience. I'm not familiar with Kerdi but need to study it. I do know there is someting called Blue Seal which is supposed to be the cat's meow and is like a liner or sealer you can paint or roll on.

  3. #3
    Homeowner geniescience's Avatar
    Join Date
    Nov 2005
    humid summers hot, humid winters cold

    Default taboo, not allowed to ask these Q's, boy oh boy are you going to get in trouble

    Quote Originally Posted by Da3dalus
    .... slab on grade...

    1. ...1-1/2" elbow out of the 2" trap ...

    2. ... 2003 IPC, and it just says the trap shall be placed as "close as possible" to the fixture outlet... is 30" OK...

    3. Worse comes to worst .... downsize? .... bottleneck at some point.

    4. .... protect the subfloor. I have a concrete slab. Isn't the membrane less critical? Can I get away with laying the membrane flat on the floor? Can I avoid the membrane altogether? Who cares if water seeps into my slab?

    5. .... cat's meow (as compared to mud & membrane)? What's the lead time to get it? Do any of the usual places (HD, Lowes, Ace, etc.) sell it?
    Amazing !! Good questions. You hit the nail on the head every time. Daedalus you could be a spy for other side. You're too smart.
    Furthermore, every single one of your questions touched on a taboo subject.
    You are right every time.

    More specifically, I'll give you my version of the facts.

    2.) yes, the trap CAN be wherever you put it. BUT, it is real wise to put it under the drain, and all it takes is a few minutes with a grinder and a cheap blade. It makes a lot of evil dust that you can diminish significantly with water spraying down on it while you cut.

    3.) Does the entire run of pipe 1.5" have to be replaced?

    Sometimes when it is just too complicated to replace all the piping, people leave the old pipe. In that case they put a reducer to come down to 1.5" so the new shower drain will still fit on the old pipe. That is what i had to do in one case this year. This means the 2" drain goes into a reducer which goes into your old pipe which is 1.5".

    Does this mean the whole thing drains more slowly? NO, in 99% of the cases. The code (requiring 2" in new construction) has a built-in margin of safety, and even 1.5" is still far larger than the minimum needed in terms of physical reality. We can discuss this at length, including venting.

    If this gets discussed in the open, on the internet, many people will be cautious because they don't want to leave permanent recommendations on record, for an anonymous pubilc to "not follow" code. I know I have been hated for having mentioned ways to work around the requirements of Code.

    A larger drain is a good thing. Many people have been known to make use of an existing drain, 1.5" in diameter. My saying this is not a recommendation.

    4.) Fact: Phoenix code may allow you NOT to have a membrane, on a ground floor concrete slab on grade, and this is because the moisture that does seep through the grout is not a big concern in the eyes of those who wrote the code back then.

    5.) If the goal is to have a waterproof membrane as close as possible under the tile, than it has to be on a slope.

    Three (3) ways to do this. One is a hard cement-coated foam tray, already waterproof and tile-ready. made by Wedi. Another is to trowel glop onto a slope you make, and let the glop become rubbery. Two big manufacturers are (HPG) Mapei and (Redgard) Custom; other liquid membranes may be as good. A continuous sheet membrane (you can overlap the seams) is (Kerdi) Schluter, which you place on a slope (that you make) or on a lightweight foam tray (that they make).

    When a membrane lays flat, it serves as a collector vessel (a container) holding dirty soapy uriny water forever, and this allows microorganisms to grow in that moist organic mess. Ultimately it becomes smellable and then visible. With no membrane on a slab on grade, you are letting the same gray water seep into your slab which means it serves as your "septic" field for the shower. Not optimal.

    If you use epoxy grout on your shower floor and walls, it could be argued that you have a virtually waterproof layer of grout sticking to tile with no cracks, and so having no membrane underneath is not crucial. That could be true. But, according to the state of the art in 2006, that might be wise in a situation where you have a floor drain for occasional use, but it is not going to satisfy the Ayatollah of Membranicity in a shower.

    Many people have been severely affected by the long-term effect of breathing mycotoxins and urea that a moldy shower and bathroom generate. Often the substances are barely detectable. But they do bring you down; they reduce your health and vitality. Search on mycotoxin and see what it does to farm animals and you'll see how it can affect humans as well. People don't live in enclosures and barns so we are able to "change air" every day, so we don't die from it.

    To get Kerdi, it can be delivered fast by http://www.tile-experts.com David Taylor 1-877-580-3745. You might order it through HDespot but you won't get information.

    1.) I'll have to re read #1 a few times or wait until others clarify. "trap"?

    Last edited by geniescience; 12-01-2006 at 07:31 AM.

  4. #4


    Quote Originally Posted by geniescience
    1.) I'll have to re read #1 a few times or wait until others clarify. "trap"?
    That's just the top part of it. Presumably it makes the turns in or under the cement.

  5. #5

    Default Moving ahead

    Thanks, guys... your responses are both timely and helpful! I am definitely going to avoid some mistakes and do this right. I'm glad you think I sound like I know what I'm doing... I'll admit now that I'm an architect, and applying book smarts to real life can be sobering.

    After much pain and suffering, I've drilled and chiseled out the lead and oakum (evil stuff that oakum), and extracted the 1-1/2" elbow. It was pretty tight... as you can see from the photos, it's under a 2x4 sill, and I almost had to cut part of the sill out. So now I can run all 2" the right way!

    I decided on leaving the existing p-trap where is it, and running straight over to it. It's just too much work to get that trap out (BTW... the "trap" I speak of is barely visible in the first photo... it goes down into the ground, and where it comes back up, it goes out to a horizontal arm under the slab. The connection is partially covered by concrete, and there may not be enough room to pull it out if I did get it disconnected).

    Now QUESTION #6: The bell of the cast iron trap I now have access to is just short of 3" inside diameter. I'm inserting a 2" ABS street elbow, so there's about a 3/8" gap all around. I'm thinking about packing it with marine epoxy putty. Or maybe using a rubber 1-1/2" to 2" connector I have (it fits pretty tight). Or perhaps get a regular (not street) ABS elbow, as the bell fits in closer. Then silicone the crap out of it. It there a better way to go ABS to leaded cast iron?



  6. #6


    Here's where I hope some knowledgeable person comes with a REAL solution... I've done "handyman" style plumbing on a very very similar situation. The way I worked around this ... in my particular case.. was to put a 4" pvc pipe into a 4" bell. I stuffed paper towels around the pipe and packed it in (since I didn't really know what else to use) then I used elastomer caulk. Nowadays that cast iron pipe comes with elastomeric seals and using lead is virtually unheard of in this neck of the woods. As a matter of fact...lots of companies go with no hub couplings everywhere cast iron is required and the codes allow it.

  7. #7


    Personally I would go with the black rubber adapter (the kind with a big hose clamp on each end) because AFAIK that's exactly what they were designed for.

    Not a pro. Barely even qualified to be considered a plumbing dilettante.

  8. #8


    OLB... those things are great (no hub coupling, Fernco couplings, etc.) But in this case I think he has a bell at the end of the pipe to fit another pipe into. Those couplings are not made to fit the bell ends... you would have to cut the bell end off and I don't think he has the room to do that.

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    If you have an inspector, or if you want the shower to work right for a long time, crack out the concrete, move the trap to the center of the shower and do it right. That long trap arm is going to get filled up with hair and soap scum, and because it isn't protected by a water seal for quite a long distance, will start to smell rather raunchy very quickly. That trap arm just won't get scoured clean. Do it right, or don't do it...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Jul 2009
    North Vancouver, BC
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    Default Tub to Shower Conversions : Go Linear - Go ACO

    Post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-18-2014 at 07:48 AM.

    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.


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