I love PVC piping systems as I make a fortune redoing the piping systems that failed or folks just got tired of hearing toilets flushed 5 rooms away.
Even Charlotte pipe and foundry says CI is a better drainage system and they manufacturer both plastic and CI.
The facts speak for themselves
1- PVC in many cases cannot be used in under ground applications such as subways and train stations and commercial applications as many fire departments do not like to expose their personal to carcinogenic chemicals as the smoke will kill most folks long before the fire reaches the victims
2- PVC cannot be recycled as can ferrous and non ferrous metal piping systems. PVC is considered toxic waste.
3-PVC if one ever bothered to read the safety precautions on the primmer and glue then they certainly would have a cause for alarm ASK OSHA,NIOSH, MSDS , it takes a certain type mentality to never let the facts get in the way.
After all who worries about brain cancer and cancer of the liver from breathing in toxic fumes. ( I will not allow any employee of mine to use this stuff without proper respirators)
4- Plastic piping is great on certain plumbing applications like acid waste where Duriron would be cost prohibitive or Pyrex is not suited for the chemicals
5- About the erroneous statement using a "snap cutter" two things are wrong with this statement
1- Many codes will not allow a "snap cutter" to be used on cast iron (no hub) as the codes call for a chop saw as a snap cutter may leave an uneven edge TSK,TSK,TSK who knew (so much for not knowing what they are talking about, never let the facts influence your choice of tools or materials))
2- Today people can rent any tool including snakes, jetters and cast iron cutters, all the various types or chop saw even a 4" grinder does wonders on No hub.
Cast iron is quiet, safe and can be exposed to direct sun light
Cast iron has a much stronger crushing strength, great for under ground sewer/drainage systems.
Cast iron give a much greater choice of radius fittings like a 1/4 bend, short sweep or long sweep unlike a plastic ell bow. (heck of a restriction one should read Hazen - Williams flow calculations elbow VS sweep)
Cast iron is not going to be used by rodents testing their teeth as the gnaw away at it.
PVC is great for venting as long as one takes the proper precautions of using enough hangers on the horizontal piping. As for drainage many folks honestly do not like to hear water flowing through piping systems
Every no hub joint is a possible clean out, not so with plastic.
For my own home as well as all my clients I only use cast iron above and below ground and this includes venting.
When I use plastic I stated several times
Thermoplastics are non-conductors, they are immune to the electrolytic or galvanic corrosion that attacks and often destroys metal piping materials, particularly when installed underground. (Depending on soil conditions)
Copper conveying hot water at 180 degrees F is prone to failure if the velocity is allowed to be in excess of 2-3 FPS (feet per second).
PVDF can handle high temperatures up to 280 Deg. F (137 Deg. C) and CPVC and PP can handle temperatures up to 210 Deg F (98 Deg. C). (So why not think plastic for potable systems if the local code allows )
I would love to put copper / cast iron against plastic piping in an acid system or even water with lots of minerals, like well water.
Copper and CI is subject to erosion from lack of proper installation (no reaming) or poor design (excessive velocity). Copper can allow hydraulic shock to be even more intense than its steel or brass piping counterpart.
. I would never think of using copper for my main sewer piping as Cast Iron has longevity and the mass to have a very quiet system and plastic waste is one of the noisiest systems imaginable .Copper type DWV is paper thin and subject to attack from chemical action of domestic drain cleaners.
If someone is looking for rock bottom in skill level and cheap as possible installations then plastic and band iron and tie wire are the way to go.
If people want materials that have a proven track record of several hundred years of potable and non potable water/drainage applications then CI /copper is the choice of professionals.
Not everyone has the same skill level or mechanical ability thus I am all for folks using compression fittings and plastic connections. Any home owner capable of using a grinder can cut CI without the use of highly toxic chemicals.
I guess they have materials for each type of application and skill level and resale value of the property