We dont alow PVC over 5 stories here , because of fire, pvc when burned puts out hazorus fumes. Cast iron pipe has been used in high rise buildings all over world, most of buildings in New York are cast iron plbg, risers have to be ofseted every 10 Fls. Our high rise buildings here 35 Stories high is all cast irn waste& Vent and copper water pipe. Look up cast iron pipe on google in high rise buildings.
Art retired plbg