Undersink plumbing

[1111ron]

Eureka!! Now I understand. Seems I had made an assumption and we know how that works. I went back and measured the galvanized stubout under the sink and it is 1.9" OD which is a 1.5 stubout. I have been working on the 2" drain pipe outside so much and got tunnel vision with metal pipe.

 

[Tuttles Revenge]

Looking at the spec sheet, the main thing I see is that the female end has NPT threads, while the slip joint end has NPS threads.

So does using a slip joint nut and washer directly on the NPT threads of a nipple generally work, but run the risk that the NPT threads may preclude tightening the slip joint nut sufficiently?

Cheers, Wayne

Yes. Slip joint connections work against clean flat pipe threads usually with a Flat rubber washer rather than the typical beveled washer. But if there are nicks in the galvanized steel drain, which there typically are, then its tough to get a seal. The trap adapter then provides a good seal on the tapered NPT threads and provides a good clean slip joint connection in corrosion resistant brass.

 

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[Reach4]

This is similar to what Tuttles Revenge posted in #13

https://www.supplyhouse.com/Elkhart-46132-1-1-2-Copper-DWV-Female-Trap-Adapter-F-x-Slip-Joint

 

[wwhitney]

Yes. Slip joint connections work against clean flat pipe threads usually with a Flat rubber washer rather than the typical beveled washer.

To be sure I understand, a beveled slip joint washer is appropriate when the threaded end receiving the slip joint nut has a matching internal bevel to seal against. And if not, then a flat washer will sealing against the end of the pipe instead of the inside, if the end is sufficiently flat. Yes?

The spec sheet on that the Proflo trap adapter you posted says it has a "brass slip ring," is that slightly beveled, with a matching bevel on the adapter body end inside surface?

Thanks, Wayne

 

[1111ron]

This is similar to what Tuttles Revenge posted in #13

https://www.supplyhouse.com/Elkhart-46132-1-1-2-Copper-DWV-Female-Trap-Adapter-F-x-Slip-Joint

Wouldn't a copper to galvanized connection cause "Dissimilar Metal Corrosion" and eat up the galvanized threads? Some say Brass will as well.

 

[Tuttles Revenge]

To be sure I understand, a beveled slip joint washer is appropriate when the threaded end receiving the slip joint nut has a matching internal bevel to seal against. And if not, then a flat washer will sealing against the end of the pipe instead of the inside, if the end is sufficiently flat. Yes?

Yes, the flat washer is the correct piece for sealing against straight pipe, the use of a brass friction washer between the nut and the rubber washer are also helpful.

Wouldn't a copper to galvanized connection cause "Dissimilar Metal Corrosion" and eat up the galvanized threads? Some say Brass will as well.

Not that I've ever experienced. We're required to connect copper to steel water pipes through 6" of brass material. Never heard of brass reacting with steel in such a manner. Honestly I've never seen the effect from copper stuffed into steel water pipes either when we tear that stuff out. But maybe thats decades down the road.

*Just noticed the reply was to the copper trap adapter**