When we run the water from the sink, it starts to back up almost immediately, and then slowly drains. When we use the dishwasher, which drains directly into the sink drain pipe, there is no backup into the sink, but the drain makes weird gurgling noises. If I plunge the sink, air bubbles come up, and after just a couple plunges the sink drains; however, if I run the water, it fills right back up again.
I have an s-trap under the sink and the drains goes directly into the basement, so it’s moderately accessible. I’ve tried snaking the drain from the drain clean-out plug, but everything seems clean. I’ve also tried the typical off the shelf drain cleaners (drano, etc.).
The dw should be before the trap,unless you have a seperate trap for the dw.Is the line vented? Why was an S trap used instead of a p trap? I would install a p trap and use a loop vent if a regular vent cant be installed.You could use an automatic air vent,but those things arent very good in my opinion.Did you do the new work or a plumber do it?
There may be a partial vent blockage. If it’s offset(the vent), the blockage may be in the bends. Assuming that there even is a normal vent extending through the roof that the drain connects to, it should be professionally cabled all the way through. In the case there is no vent, install one. In either case you have a vent problem.