Clean Check prevents sewage backup into plumbed structures as a result of a plugged sewer system, excess volume in the system or groundwater flooding. Flapper installs discretely outside - up to 12' below ground level. Easy installation for home improvement. Above ground outdoor maintenance accessibility eliminates hidden access indoor applications, and the sewer odor and mess of indoor maintenance. RectorSeal New Style Clean Check Flapper; complies with UPC, IPC and IRC codes and ASME and ICC-ES standards; no manhole required to use flapper; 3" or 4". Recommended for PVC and ABS. FOR THE TRADESMAN: RectorSeal is recognized as a leading provider of quality solutions for the professional trades serving heating, ventilation, and air conditioning (HVAC/R), plumbing, electrical, and construction markets.