Bergall. Call a licensed master plumber! I have been a licensed plumber for nigh on 40 years & still have not had a blocked drain in one of my installations because of faulty work, there will always be reasons like root ingress, detergent buildup or grease buildup. PVC is good for stoping root ingress however inspection openings not screwed on properly or penetrations because of extensions or the like have the potential to stuff the integrity of your sewer drainage.
You need to know what is causing the problem & fix it, dont just try to ease the pain. Call a licensed plumber.
Regards Bob