It’s important to acknowledge that both plastic (PVC) and cast iron drainage is built to do a job, and generally speaking each material does this with great effectiveness. However, it would be inaccurate to pretend that PVC and cast iron are essentially the same material, when in fact they each have very different attributes.
Cast iron drainage is non-combustible, in other words it cannot cause a fire nor does it react to fire. As such, it is the perfect material to be used where there may be a risk of fire or concerns about fire safety. That’s not to say PVC is not fire safe, however it is more combustible than cast iron.
A defining feature of cast iron is its durability. It is an extremely hardwearing material and ideal whether you’re using it for water drainage or soil drainage. PVC is not as durable, although it is usually more cost effective in the initial period.
Because cast iron is so durable it is built to last a lifetime, in fact a couple of lifetimes. The drainage systems at Versailles were, and still are, made from cast iron, and so have lasted for a couple of hundred years with minimal problems.
Cast iron is very resistant to corrosion and so it is able to carry potentially corrodible substances without significant problems, of course this depends specifically on the chemical that’s being transported.