The WC system is a wafer chech valves that is available in PVC from 10 inches up to 20 inches, and in PVDF from 2 inches up to 20 inches in PP. The O-ring material is enclosed with FPM together with EPDM or PTFE. It can be acquired with stainless steel springs.
During the DIN or PVDF pipe build up, spacers are not needed. Spacers are needed during the operation of Schedule 80 pipe.