This vertical pipe is connected to the kitchen sink above and the utility tub in the basement. When the utility tub is used, the drain in the floor is backing up. If the sink is run upstairs it doesn't back up. Odd, but makes me think it's a flow issue. I tried to remove the clean out to snake but it's stuck. I'm thinking I can cut the PVC or remove one of the upper clamps and snake from there to see if I can knock out whatever's causing the backup or slow draining. I did grab a bottle of "main line cleaner" from depot and let it sit overnight and then flushed with boiling water, the water level in the drain went down a bit but it still creeps up when I run the utility tub.