Ironranger mn i m pretty sure what they meant was that if you use 1 2 pex you could have a restriction since it s smaller than copper.
Can i use pex for tub spout.
There is no way to secure pex adequately to keep a tub spout from flopping around.
Soldering to the nipple with the pex attached is not optimum but can be managed if you have room to tightly wrap a water saturated cotton rag around the copper and extended over the pex portion.
2 reasons i learned.
The interior diameter of pex is actually a fraction smaller than copper this forces water to come out of the shower at the same time as the tub spout.
Pex to tub spout.
After investigating the 3 4 will work just fine no restrictions.
Long story short it is unacceptable.
The tub spout can be copper brass or galvanized pipe.
2nd reason pex is flexible and the spout relies on the pipe for support.
Copper keeps the spout in place.
Copper is the only professional installation material.
With a built in diverter you could use a pex drop eared ninety degree female adapter and a nipple but that is more trouble than it is worth.
When pex is used on those tub spouts the excessive back pressure sends water up the shower.
It is only created on tub spouts where a diverter closes off the easier path out the tub spout to send it to the shower.
Pax has a smaller inside diameter than copper when you will turn on the spout your showerhead will also be dripping if you read the manufacture instructions it will say do not use pex for spout level 2.