Screwing plastic spout-threads to metal nipple advisable?

[Minni]

I've seen people state that plastic threads don't pair well with metal threads. Well, if that's the case, why do faucet-suppliers insert a plastic liner inside metal spouts. The plastic liner contains internal threads that are meant to be screwed onto a metal combo consisting of adapter+nipple. How can that be advisable?

For example, the Delta pull-down-diverter tub-spout is that way. I'm referring to the IPS option. I believe this spout offers both IPS & CWT options.

 

[Breplum]

Sure, plastic isn’t optimal, but since the spout is accessible it’s not truly a risk. We use the delta pull down ips with easy adjust depth. The ips adapter is brass and never had an issue with the spout internal plastic part because it’s actually an o ring seal. Professionally I prefer Grohe spouts above all others.

 

[Sponsor]

 

[Minni]

Sure, plastic isn’t optimal, but since the spout is accessible it’s not truly a risk. We use the delta pull down ips with easy adjust depth. The ips adapter is brass and never had an issue with the spout internal plastic part because it’s actually an o ring seal. Professionally I prefer Grohe spouts above all others.

How does the American-Standard Pull-Up diverter-spout compare? Because i bought one of those for approx. $26. It's made of metal.

 

[John Gayewski]

Faucet parts are probably not what "they" are talking about when saying metal and plastic threads don't mate well. They are most likley talking about npt parts of different material. The metal threads tend to take any path they want through the plastic threads. This makes cross threading a common mishap.

Faucet threads and parts usually have different threads and the material is likley not soft pvc.

 

[Minni]

Faucet parts are probably not what "they" are talking about when saying metal and plastic threads don't mate well. They are most likley talking about npt parts of different material. The metal threads tend to take any path they want through the plastic threads. This makes cross threading a common mishap.

Faucet threads and parts usually have different threads and the material is likley not soft pvc.

I see, thanks. So it's just a matter of different quality plastic in different products, that causes threading to be problematic.

Meantime i'm in midst of a way more complex issue, cuz my shower-pipe & shower-arm wobbles. See, due to my 50's home, i don't have standard studs/drop-ears securing the shower-arm. Instead the wood-beam is internally to the left of the showerArm hole. Yes, there's expanding-foam, but that would not be secure. So what do you think of slicing a rectangle out of the old-fashioned wallpaper that's on barely-used bathroom on reverse side of my bathtub?

My attached pics explain it all. What should be the approx. cost for fashioning a hinged access-door via the other bathroom, and securing the shower-pipe with a bracket, as well as to re-tile the square surrounding the tub-spout+trim near the tub?

 

[Sarg]

The one warning I have read from the experienced folks regarding the metal-plastic mix is ..... Do not use a metal male fitting with a female plastic because the chance of the plastic female fracturing is high.

 

[Jeff H Young]

use a brass nipple.
On a side note rather than create a tile job if you are cracking open the other side of the wall to fix shower head strapping couda just done the work from that side?