New tub drain plumbing advice

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Alex1

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Hi guys,

I'm installing a new bathtub and wanted to run my plan by you see if you can spot any mistakes.

The new drain is 1.5" PVC. This should give you the idea:

1682044339471.png


Some pics of what I found as I removed the old tub and exposed the trap:

1682044339503.png


1682044339520.png


My plan is to remove everything starting with that mission coupling and build it up like this:

  1. Use a 2 in. x 1-1/2 in. DWV Flexible Reducer to go from 2" ABS to 1.5" PVC. I think the reducer can act like a slip joint and give me more flexibility with aligning tub drain pipe and the trap.
  2. Connect 1.5" PVC pipe and P-Trap with Union and Plastic Nut. Again, union will give me flexibility with alignment.
  3. Glue up the tub drain and the trap, ensuring that the horizontal part of the assembly has a slight downward slope towards the sewer inlet.
  4. Test for leaks and bury the whole thing in dirt.

A picture is worth a 1000 words:

1682044501254.png


Do you see anything wrong with my plan?
 

Breplum

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No union traps allowed if inaccessible, because they can leak.
Glue joint trap is the way to go if buried. And, only shielded rubber couplings (they make all realm of size transitions. The type you illustrate sag and offset all to often.
To adapt the tubular to the trap, we always use T150 for that.
If using banded couplings, it is preferred and required to use a plumbing t-torquer for proper tightness.
 

wwhitney

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And, only shielded rubber couplings (they make all realm of size transitions. The type you illustrate sag and offset all to often.
For what it's worth, the style shown is allowed to be used underground, and the shorter banded Fernco Proflex / Mission Bandseal style is not. [Although maybe if you don't backfill, it's not underground?] Because of the sagging concern, it would be important to be sure the backfill underneath the coupling is well compacted so that it is full supported along its length. Or a banded version of the underground style could be used, but I don't see a 1056-2/150RC on Fernco's website, it's an odd omission as they have basically all other nearby size combinations.

Also, that new overflow has a slip joint fitting, so an access panel for it will be required. Which, depending on what else can be accessed, might allow an additional slip joint connection. Otherwise everything should be glue joint or a listed rubber coupling--ASTM C1173 for underground (Fernco style), or ASTM C1460 for above ground (Proflex/Bandseal style).

Cheers, Wayne
 

Alex1

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It's clear now that the best thing is to just glue the underground parts. I'll use 2" all the way because I read in another thread that 2" would be easier to clean out if there is a clog at some point. Here's the new plan:

1682096952636.png
 

Tuttles Revenge

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either 2" or 1.5" trap will allow a 1/4" snake to pass. A smaller trap will scour itself clean better as there will be more velocity. But plastic isn't likely going to have issues. Dealers choice there IMO.

We install that tub and that waste and overflow All the Time! Silicone the overflow gasket to the tub and the overflow when you're setting it the last time. They're prone to leaking since the screws are so far apart.
 

Breplum

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For what it's worth, the style shown is allowed to be used underground, and the shorter banded Fernco Proflex / Mission Bandseal style is not. [Although maybe if you don't backfill, it's not underground?] Because of the sagging concern, it would be important to be sure the backfill underneath the coupling is well compacted so that it is full supported along its length. Or a banded version of the underground style could be used, but I don't see a 1056-2/150RC on Fernco's website, it's an odd omission as they have basically all other nearby size combinations.

Also, that new overflow has a slip joint fitting, so an access panel for it will be required. Which, depending on what else can be accessed, might allow an additional slip joint connection. Otherwise everything should be glue joint or a listed rubber coupling--ASTM C1173 for underground (Fernco style), or ASTM C1460 for above ground (Proflex/Bandseal style).

Cheers, Wayne
Says "underground"...not taking the time to look up UPC listing. Inside dwelling, I've never had an issue with inspector rejecting two band shielded, listed couplings. But I've only been at this profession for 49 years, almost all inspected jobs.
1682120941530.png
 

wwhitney

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But I've only been at this profession for 49 years, almost all inspected jobs.
Absolutely, you've got 100 times the experience I do, which is why I prefaced my remarks with "for what it's worth."

UPC 705.10 says "Mechanical couplings used to join different materials shall comply with ASTM C1173 for belowground use, ASTM C1460 for aboveground use, or ASTM C1461 for aboveground and belowground use." I don't believe there are many products listed to ASTM C1461 on the market, usually it's ASTM C1460 or ASTM C1173. So this above ground / below ground distinction is in the UPC.


And as I expect you know, the no hub coupling you show is neither ASTM C1460 or ASTM C1173. It's designed for no hub cast iron only, and for that material it can be used above or below ground. Not applicable to the OP. Although I imagine they would work well for plastic, particularly in the 2" size where no hub cast iron and plastic have identical diameters.

Oddly enough, the only UPC references I see for using the ASTM C1173/C1461 couplings is for joining different materials. Seems like technically it's a violation to use them to join ABS to ABS or PVC to PVC, even though that is a common and very useful application. That has always perplexed me.

Cheers, Wayne
 

Breplum

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Wayne, you are correct about the technical violation. To join dissimilar materials one is supposed to use the listed couplings with the specific materials identified. Those couplings most often are of the smooth stainless steel band style, but, that may be the particulars of getting official 'listings' with UPC/IAPMO.
 

Tuttles Revenge

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Most inspectors allow us to install No Hub bands on plastic to plastic of the same size simply because they are the same diameter. I you use them to transition from plastic to cast iron, the band will deform because the CI is ever so slightly smaller in diameter, but enough. But when you purchase the transition band from plastic to cast, you will notice that they appear to have the same diameters as well.. basically its a BS way to spend more money for a product with a listing.

The label on transition bands says something to the effect of. Transition from CI / PL or Steel to CI / PL or Steel...
 
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