you could actually put plastic up before the studs and then staple and. duct tape , then use  regular insulation . i guess depends on what its being used for and where you live as well . i have seen kits on eBay and amazon , may  not be worth it ????

We did not charge him for it, because our contractor cleared it with one of those long plastic snake things and removed a clump of hair.

Be suspicious of replaced plastic  plumbing at the hot water heater and under sinks.

Disclaimer: This is based on adding a door in a single-family home in Missouri; the requirements for multi-family and in other jurisdictions are probably different.If you have any electrical outlet boxes in the fire-rated wall, they probably need to be steel, or the fancier plastic ones... the cheap blue ones aren't rated for it.If you have to bring a pipe through the fire wall, there may be some requirements about that.  

Ask me how I know this....2) the hardware at ikea for cabinets (drawer pulls, etc) is not the best, and needs some patience and tweaking, but can give you a really, really cool look for a lot less than custom.  3) if and when someone tears through the outer laminate (plastic) layer on them, water will destroy them in no time (think under-sink leak)

Galvanizing copper is a chemical impossibility.Projected lifespan of galvanized piping is typically projected at 60 years, but it can be less or more depending on the water quality of the source.Copper is generally projected at 80 years but same caveat.Lifespan of plastic is for all practical purposes, infinite. 

@Bryan Sowieja  well not a popular thought but its realistic.having owned a bunch of rentals in Mississippi we get some pretty large tenants in those areas.And special toilets are required along with reinforcing sub floor below.. and they can wreak havoc on plastic tub shower combos... can't comment on if you can exclude them. but if you rent to folks that you know are quite heavy no matter there physical type  IE professional athlete  power lifter.. cage fighter  WWF or whatever... you do have certain realities in the bathrooms that need to be addressedI have had more than one 400 lb plus tenant have the toilet give way on them during the act. 

Is PEX the same thing as pvc; if so, I thought we couldn't mix copper with plastic? 

If my buyers see pre-formed plastic on the floor they assume the entire place is junk and pass.

(C) Buy those adjustable plastic grids from the big box stores and cut them to size and insert those green filter into them?