Sink Backup Issue
Have a basement utility sink that has performed with no issues for years. In recent weeks the drainage has slowed and now cannot empty. Liquid drain cleaners and augers have been used to no effect.
PVC piping which was constructed in sections was taken apart to find no obstructions. Water was physically removed to a submerged pump. 30 minutes later water entered the sink to 1/2 inch. Water removed again only to rise to the same level. Can an air block be a possibility? The sump pump sucessfully evacuated the water when scooped out from the sink.
Is this a known issue? Looking for guidance from an informed individual.