Can I... use fernco donut inside schluter drain?

Discussion in 'Shower & Bathtub Forum & Blog' started by diymatt, Jul 13, 2021.

  1. diymatt

    diymatt New Member

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    Just wondering if kosher to use a Fernco donut fitting inside a schluter (2in PVC) drain? I assume they make one that would seal up inside there as if it were 2in PVC, then connect to an old 1 1/2in iron pipe that heads into the trap below. The issue is the old iron pipe is circa 1938 and comes up out of the concrete basement floor. I want to raise the subfloor as little as possible, and minimize risky contact with that old pipe.

    For background, we've removed an old tub from this basement bath and have a stub of 1 1/2 in pipe (good threads, at least) coming out of the concrete floor. My wife wants a steam shower and has chosen an EPS shower pan (custom) from a company that designs them to work with Schluter drains. I assume using a different brand of drain with a shorter profile is a no-no given the bonding requirements for the Schluter membrane? Building up the subfloor to accommodate the Schluter drain body makes the shower too short, and cutting out concrete around the old pipe is dodgy given the age. I've looked through a couple threads on this issue and wonder if there are any shortcuts available.

    Here's a pic of my pipe, with a 2in PVC spigot adapter end showing. Using a 2 by 1 1/2 iron bushing would get me into the Schluter drain w/ 2in threads, but still requires raising the subfloor up a ton. Basement bath, of course underneath radiator pipes, so the finished height is the problem. Any ideas?

    IMG_0147.jpg
     
  2. Reach4

    Reach4 Well-Known Member

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    You are proposing to use one of these inverted from the way the top picture is shown?

    https://www.fernco.com/plumbing/donuts-o-rings/donuts

    xdo-donuts-main.jpg

    Maybe show what you are trying to connect to, minus the PVC adapter in your picture, although I guess that will just show a pipe sticking up.

    Are you saying that the drain you intend to use has a 2-inch schedule 40 pvc tail built in to its bottom?

    1.5 inch pipe IPS OD is 1.900 inches. 2-inch schedule 40 PVC is 2.067. I expect that to be too thin to accommodate a Fernco Donut. You might get by with some 3-M marine adhesive to fill the gap. Even lead is maybe theoretically possible. Not for you. I am not a pro.

    I wonder if you could shove some oakum and then lead wool into the space. The 3M adhesive appeals to me, but I don't have personal experience.

    If that drain has a 2 inch FIP bottom, how about a brass bushing?

    https://www.supplyhouse.com/Bluefin-BRB200-150-2-x-1-1-2-MIP-x-FIP-Brass-Bushing-Lead-Free

    brb200-150-1.jpg
     
    Last edited: Jul 13, 2021
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  4. diymatt

    diymatt New Member

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    Thanks for your time! Yes, inverting a donut is what I'm wondering about. Yes, it is just a pipe sticking up (left the PVC on to protect the threads during carpentry and in case I end up using as it is).

    Sorry for not being more precise- I've done only a handful of showers and learn something new each time. For this one, I found fernco donut #P22U-139, which claims to mate a 1.5 in PVC pipe into a 2in iron hub. I see what you mean about an impossibly thin donut, but I found different measurements... Indeed the old steel pipe is 1.9 inches OD (1.5 nominal), but the 2in nominal PVC spigot/pipe end of my adapter is 2 3/8 OD, which I checked against a scrap of known 2in PVC pipe I had. That's the end that would fit inside the Schluter drain body (stainless, presumably a friction fit with a skinny little rubber sleeve under compression in between).

    And yes, I had my hands on one of those brass bushings just this morning and saw that it would work but raise my subfloor a ton (4+ inches).

    Part of my problem is I don't have the Schluter drain in hand as I've yet to order it and have never used one. They make a 2in threaded version that would accept the bushing and leave me with a too-short shower. The standard version accepts 2in PVC pipe into its hub, presumably with its own skinny little fernco-style boot in there. The Schluter site has some measurements that appear to show what I'm suggesting. That's what I'm wondering if anyone has tried this, putting a donut up into that Schluter drain. Would it be reasonably watertight? Overlapping the drain body as much as possible with the old 1.5in pipe seems the safest way to max my shower height.

    I see my old Lowes here has the fernco in question in stock for ~$5... will pick one up in the am and have a look.
     
  5. wwhitney

    wwhitney Well-Known Member

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    I think I have to disagree, this is likely the best solution. If your stub is a nipple, there's a chance you'd be able to unscrew it from a trap below, leaving you with below slab female threads to start from.

    I don't understand this comment. Are you saying that with the donut, you'd be cutting the existing pipe down closer to the slab, to get the drain body just above the slab, while with the existing threaded pipe, the threaded drain body would end up noticeably higher than that?

    Cheers, Wayne
     
  6. diymatt

    diymatt New Member

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    I had been wondering if I could use the donut inside the Schluter drain body, to get the old 1.5in pipe as far up inside the drain body as possible, without cutting the slab or even the pipe. That would minimize how much I have to build up the slab/subfloor to keep the shower from being too short. I looked over the donut this morning at Lowe's and saw that it doesn't fit inside a 2in PVC hub, not even close. One that would fit, would be awfully thin as Reach4 pointed out, if it even exists. And it would still require 3 inches or so of new subfloor.

    So I guess I'm looking for a pep talk to get me cutting into the slab to get at the next fitting. I see water in the trap about 6 inches below the floor when I look down into the pipe. I see pics of others' similar situations on the site. In our 3 years here I have mated up new PVC to old pipe at 3 other drains in the house, successfully, where the horizontal runs of iron pipe had problems. More will come, so what's another one now, right? Even if its under concrete it shouldn't be any worse than what I've done so far.

    What should I expect to find? I assume the slab is ~3inches thick, was there any standard practice about burying plumbing? Heavy clay soil here.
     
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    If you're getting a permit and inspection, the first thing you need to find out is if the inspector will allow you to keep the 1.5" pipe! Today's code requires a 2" drain for a shower. They MIGHT let you utilize the 1.5" pipe.

    The piping under the slab is now 60-70-years old? Cast iron, and especially if there's any galvanized, doesn't last forever. It would be a major shame to put in a new shower and later find out that the trap and drain lines rusted out.

    So, I'd want to crack some concrete, and get down far enough to at least take a good look at the p-trap. Depending on how the line is run, if a 2" or larger section is near enough, I'd replace it to that point with new 2", then, you can put your trap, drain, exactly where you want them, and at the best depth to accommodate your needs.
     
  8. wwhitney

    wwhitney Well-Known Member

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    FWIW, the UPC requires a 2" drain for a shower, but the IPC (in force in MD) allows a 1.5" drain for showers with 5.7 gpm of showerheads.

    https://up.codes/viewer/maryland/ipc-2018/chapter/7/sanitary-drainage#709.1

    That said, 2" would be a better choice if not too difficult.

    Cheers, Wayne
     
  9. Reach4

    Reach4 Well-Known Member

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    Without dimensions of the prospective drains, it would be hard to know what to do. But anyway, https://www.ferguson.com/product/st...ule-40-abs-flush-bushing-adwvfbtkj/_/R-801022 would glue into a 2-inch ABS hub.

    If you could find a short piece of schedule 160 PVC pipe, you could tap the inside for 1-1/2 inch NPT. Then screw that onto your 1.5 inch steel pipe, and glue a PVC hub onto that. 2-inch schedule 160 PVC pipe is not easy to find. It probably sits in a scrap bin of a well driller somewhere.
     
  10. diymatt

    diymatt New Member

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    Since no one here seems concerned about digging through the concrete, I did just that. Here's a pic- the trap (water I can see down inside) is just under the dirt. What's my next step here? Looks like the nipple is stuck in there with lead, but I've not worked on one like this before so I'd really appreciate the input from those who have.

    Again, the ultimate goal is to have the end of a 2in PVC pipe level with the subfloor. The Schluter shower drain would overlap that by 2 inches down below the subfloor and mate with the shower pan 1in above the subfloor. I assume a Fernco coupling is not kosher or even reasonable here, cutting off the nipple and using a 1.5in to 2in adapter coupling with a stub of PVC pipe coming up to the subfloor...

    IMG_0171.jpg
     
  11. Reach4

    Reach4 Well-Known Member

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    Good. Now you can remove that lead, measure inside the hub with a digital caliper, and get the right Fernco Donut. Click Inbox, above. I suspect you can use a 2-inch pvc pipe into the donut. But check the measurements.


    There are various descriptions in the forum on removing the lead. Basically drilling out much of the lead, at least in one area. Then prying with a flat blade screwdriver.
     
  12. wwhitney

    wwhitney Well-Known Member

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    A couple additional comments:

    Once you have the iron riser removed, you'll want to evaluate the condition of the trap and decide if it's going to last as long as your shower will. You don't want to have to replace your new shower pan in 5 years because the trap rusted out and won't keep a seal. I'm not sure how to make that judgement, you may want to excavate to reveal the trap exterior, and possibly poke it inside and out in various places with a flat blade screwdriver.

    If the trap is usable but the hub inner diameter is too small for a 2" PVC pipe, then you could use a 1-1/2" pipe. To adapt that to the 2" outlet of the Kerdi drain you'd need a bushing or reducing coupling that presents a conical inner surface when the 2" side is facing up, to avoid standing water/scum at the reduction. I believe those are available.

    Cheers, Wayne
     
  13. diymatt

    diymatt New Member

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    Thanks- your reply came as I was watching youtube videos on how to do the removal. Torching the lead looked fun but with nowhere downhill for it to run that seems useless. Drilling/prying is easy enough as I have a straight shot at it down through the hole, will make sure I get the whole oakum mess out of the pipe rather than letting any of it stay in the trap.

    Those little rust nodules seem to pop off pretty easily. Will get after this again in the am. I guess this stuff was used to allow for joints where one couldn't get a wrench, and allow tiny angle adjustments beyond 45's and 90's?
     
  14. Reach4

    Reach4 Well-Known Member

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    Lead+oakum was used, even if there was good access for threaded joints. It has good merits. Less likely to stress joints and causing cracking of fittings.

    Get your digital caliper on order.
     
    Last edited: Jul 19, 2021
  15. diymatt

    diymatt New Member

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    In process... the lead just keeps going and going. There's a nut of some sort on the end of the pipe, and its not quite centered so the drilling is a PITA. I get slimy black stuff on the tip of the bit so I think I'm getting there. Any ideas to loosen the thing up at this point?
     

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  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Once you get most of the lead out, try sticking something in the pipe and rocking it back and forth some.

    Don't crack the hub, but it should be pretty tough.
     
  17. diymatt

    diymatt New Member

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    Firm, persistent hammer taps finally worked about 10:30 last night... there was a coupling screwed onto the end of the 1.5in pipe, and THAT was oakum'ed into the 2in bell and they'd rusted together a bit. The lead went on for over an inch, and the oakum or putty or whatever that was had dried into a tough crust. Headed to home despot for the donut, all my ferguson's in the area are sold out of them! The trap is clear and solid considering its age, so I think we're a go.
     

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  18. diymatt

    diymatt New Member

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    Success, I think. Once I popped in the pvc pipe the fit became quite tight. Thanks for the encouragement! One more question though- I intend to pack clay soil in around this, enough to cover the fernco. Then cement, though it'll be a little thin in the center since I need to leave room for the body of the drain below the subfloor. Would it be better to dig deeper and get concrete down below the fernco and leave a little open space around the connection? I assume it's bad to encase the fernco and everything in concrete in case of repairs or replacement down the line.
     

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  19. wwhitney

    wwhitney Well-Known Member

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    I have not used the Fernco donuts before, but as your hub is so deep, I assume it is deeper than the Fernco? If so you could press the donut into the hub a little more, not sure if that would be a good idea or not.

    As to the concrete repair, I would think you'd want to backfill around your plumbing with a little a gravel, even if you backfill everywhere else with native soil. Then box out around the drain a little, e.g. with a scrap of 3" or 4" DWV pipe. And then perhaps if you're worried about support for the shower pan, fill any remaining void with sand to the extent possible at the last opportunity before setting the pan.

    But the above is rather seat of the pants, so I might have some of the details slightly off.

    Cheers, Wayne
     
  20. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Retired Systems engineer for defense industry.
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    While the shower shouldn't leak if done right, there might be some moisture from the ground...clay soil expands when it gets wet by as much as 10% or so...I'd pack it with fine gravel or sand. Depending on how big the hole is, you might need some concrete in there.

    The bowl on the Kerdi drain is fairly large, but not hugely deep. YOu want sturdy support for the flat part of the flange on the drain, and that may take some concrete. Kerdi Drain.jpg
     
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