Confusion about joiningTubular PP to Steel piping

[David Pecnik]

Hello to everyone,

I'm at my wit's end on this one, probably because I have done so much research, I've overloaded on it.

Here's my situation. I have a 1 1/4" tubular PP drain pipe that I need to attach to "in the wall" what I believe is a 1 1/4" steel pipe. The OD of this steel pipe I measured at 1.66" and an inner diameter of around 1 1/4". I need to connect that plastic drain pipe to the steel drain pipe in the wall, but I'm not sure of what size coupler to purchase. At first, thinking the steel pipe was 1 1/2", I ordered a reducer nut and washer that went from 1 1/2" to 1 1/4". However, the nut turned out to be too wide. When I tried screwing on a 1 1/4" nut on the steel pipe, it was too small. So I next ordered a flexible coupler 1 1/2" to 1 1/4"--again the 1 1/2" end was too big. The 1 1/4" end, fit over the pipe. I'm now at a complete loss as to what measurements I need in a coupler to allow me to make this connection.

Any guidance would be greatly appreciated!

David in OH

 

[Reach4]

The fitting to connect a threaded 1-1/4 steel pipe to polypropylene trap is a 1-1/4 threaded trap adapter.

Here is one in copper/brass:

 

[Sponsor]

 

[David Pecnik]

I'll give that a shot. Thanks for your help and a Merry Christmas to you!

 

[Kreemoweet]

Ordinarily, an 1 1/4 tubular drain pipe can be connected directly to an 1 1/4 NPT-threaded metal drain pipe,
i.e., no adapter/coupler needed (although it's best to use a trap adapter as mentioned). The threads on the steel pipe, and the 1 1/4 slip-joint nuts for the tubular drain
should match up, but old steel pipe threads get corroded, and the end gets raggedy and loses the starting threads.
You might be able to clean up the steel pipe threads sufficiently with wire brushes, triangular files, and whatnot.
If not, you might be able to rent a manual pipe threader and clean up the threads, if there's sufficient room. Maybe
a "rubber" coupler specifically made to fit 1 1/4 schedule 40 on one end, and 1 1/4 tubular size on the other, could
be found. Sometimes it can not be avoided, that the pipe nipple coming out of the wall has to be replaced.
It gets hairy. Good luck!

 

[Reach4]

You might be able to clean up the steel pipe threads sufficiently with wire brushes, triangular files, and whatnot.

A tool that I don't find to exist, but ought to exist, is a two-piece split-die thread chaser for NPT pipe.

 

[David Pecnik]

I had the opportunity to try to install the 1 1/4" female trap adapter today. The female 1 1/4" is too small for the drain pipe. The slip joint and washer included did fit the end of the tubular pp pipe like it should.

I must not be measuring this steel pipe properly, but now I figure it's a 1 1/2" steel pipe. The house was built in 1956--could it be 1 1/2" piping? If so, what connector do I need to join these annoying pipes.

 

[Reach4]

I must not be measuring this steel pipe properly, but now I figure it's a 1 1/2" steel pipe. The house was built in 1956--could it be 1 1/2" piping? If so, what connector do I need to join these annoying pipes.

If you measured 1.66, it seems unlikely to be anything but 1-1/4 pipe.

Your threads are probably messed up. Can you clean the threads up?

I think I have a long term to-code solution. Connect your pipe with a Fernco 3003-150 to a 1-1/4 inch spigot trap adapter.

https://www.pvcfittingsonline.com/1-1-4-dwv-pvc-trap-adapter-male-sp-x-sj-d113-012.html That would not be as nearly elegant-looking as cleaning up the threads on the pipe and threading on that 1-1/4 FIP trap adapter.

I don't find a flex coupling that would connect your pipe to 1-1/4. I could find one that connects your pipe to a 1-1/2 inch trap arm. That would not be to code because you would be reducing after the trap arm, and even if not worried about code, it could form a place for a blockage to occur. Fernco 3010-150 or Fernco P3010-150 or Mission KT-150 would do that. If a blockage did occur, it would not be that hard to access for cleaning.

1-1/2 inch copper is about the same OD as 1-1/4 schedule 4o pipe.

 

[David Pecnik]

Can you tell me more about these flex couplings, attach a pic if possible, and what size would I be looking for?

I'll see if I can get a good picture of this drain pipe threading. It is in a difficult position.

 

[Reach4]

https://www.fernco.com/dimensional-drawings/3003-150

https://www.menards.com/main/plumbi...proflex-coupling/3010-150/p-1444430437561.htm
https://www.supplyhouse.com/Fernco-3010-150-1-5-x-1-5-ProFlex-Coupling-Copper-to-Tubular
https://www.homedepot.com/p/1-1-2-in-Copper-to-1-1-2-in-Tubular-Neoprene-Shielded-Coupling-P3010-150/100181044

 

[David Pecnik]

I was able to snap some pics. I'm comparing the slip nut, which is hard plastic or perhaps rubber that's aged like 15 years or so, that I removed from the steel drain pipe. Incidentally, I'm able to screw this slip nut back on to the steel pipe seemingly without thread issues. Unfortunately, I had to crack it off, so I can't re-use it. Ideally I'd love to find the same sizes slip nut. As you see in one pic, it fit's perfectly on the tubular pp piping. I measured in the ID of the old nut, and it's around 1 5/8", while the adapter I purchased is only 1 1/2", and it just won't fit over the steel pipe.

I have half a mind just to glue the nut and re-use it.

 

[Reach4]

The OD of this steel pipe I measured at 1.66"

You measured that with a steel ruler? You should get a digital caliper to make better measurements easier.

 

[David Pecnik]

I did measure with a digital caliper.

 

[Reach4]

Run your fingernail around the threads on the pipe. Do you detect debris that you could scrape out with a dental pick or a defect that you could file away with a jewelers file?

I messaged you about a thread chaser.

I suspect that your broken plastic nut would screw onto that new copper trap adapter without the crack expanding. I am just suggesting that as a size comparison.

 

[David Pecnik]

I'm looking at the female trap adapter and the old slip nut. The slip nut screws into the male side of the adapter. The OD of that end of the adapter is 1.61, so basically matching the 1.66 OD of the steel pipe.

I decided to be a little proactive and instead of using the trap adapter itself, I used the slip nut and washer to see if the nut would find. Well, I think it wanted to fit, but after tightening things up, the leak is more like a river. I think this is telling me the threads are shot.

 

[Reach4]

I think this is telling me the threads are shot.

 

[David Pecnik]

What I'd like to do which I tried to do in my first post is to use a flexible coupling. I thought, at first, I had to reduce it, but now know I need a 1 1/4" steel pipe to 1 1/4" tubular pp (pvc) coupling. I bought a 1 1/2" to 1 1/4" coupler. The 1 1/4" end of the coupler fit perfectly over the steel pipe. The 1 1/4" end, however, doesn't fit over the plastic pipe, whose OD measures at 1 1/4". The ID of the coupling is 1 1/2", so it's too loose. So what coupling size do I need? 1 1/4" to 1"?

 

[Reach4]

What I'd like to do which I tried to do in my first post is to use a flexible coupling. I thought, at first, I had to reduce it, but now know I need a 1 1/4" steel pipe to 1 1/4" tubular pp (pvc) coupling. I bought a 1 1/2" to 1 1/4" coupler. The 1 1/4" end of the coupler fit perfectly over the steel pipe. The 1 1/4" end, however, doesn't fit over the plastic pipe, whose OD measures at 1 1/4". The ID of the coupling is 1 1/2", so it's too loose. So what coupling size do I need? 1 1/4" to 1"?

Choices I see:

1. Get a custom coupling made. I expect that to be expensive.
2. Clean up your threads and screw on that 1-1/4 metal trap adapter.
3. Use your latest coupling to connect to a 1-1/2 trap, and use a reducing washer to match the 1-1/4 inch tailpiece. Not quite following the rules, but probably nobody notices. That would take careful cutting of the trap arm, because you would want the trap arm pretty much butted up against the end of the pipe. However you could use an extender in the trap arm to give you some adjustablity, and avoid the custom.
4. Get a piece of 1-1/2 OD 1-1/4 ID hose, and cut off a piece to use as a bushing. Convert your latest coupling to 1-1/4 in effect. https://www.menards.com/main/plumbing/rough-plumbing/pipe-tubing-hoses-fittings-accessories/hoses-tubing/pool-spa-tubing/sioux-chief-1-1-4id-x-10-flexible-spa-hose/900-16500w00101/p-1470660863360.htm might do it, but it would look better if you found it in black rubber tubing.
5. Find a rubber 1-1/2 OD 1-1/4 ID for sale. I feel that is possible but not so likely.
6. Use the trap adapter and coupling suggested in post #7.

Doing #4 or #5 now does not prevent you from doing #3 later.

 

[David Pecnik]

Thanks, Reach4, for your help & patience,

I'll try cleaning the pipe threads. I have a wire brush and some steel wool. The problem is that the pipe is, of course, in a bad place and it's hard to get a good angle on it.

Not sure if I quite get #3. I have a reducing coupler. From 1 1/2 to 1 1/4. The 1 1/4 end fits snugly over the steel drain pipe. The other side has a 1.8" ID that would need to fit over the tail piece pipe, currently an ID of 1" and an OD of 1 1/4". Is it possible for me to convert to PVC instead of PP, since the OD of this PP piping does not match 1 1/4" PVC which is 1.66 OD. Will not the PVC tail pipe then be able to join to the steel pipe?

 

[Reach4]

The ID of the coupling is 1 1/2", so it's too loose.

The other side has a 1.8" ID

Which is it?

 

[David Pecnik]

The coupling's 1 1/2" side is 1.8 ID and an OD of 2.25". The 1 1/4" side 1.56" ID and a 1.95" OD. Thickness is .21".