So what does it mean if the kitchen sink and bathtub are really slow to drain and the toilet doesn't flush all the way? When you flush it just swirls around and doesn't suck it down. Sometimes though I come in and almost all the water has drained out of the bowl (a long time after flushing). When the toilet, sink or tub are draining I hear a glub glub sound, like when you turn a 2 liter bottle upside down to dump it out. My BIL says it has to do with the air intake. I found the air intake. How do I figure out if it's clogged and how do I unclog it? It's up on the roof. I would really rather not call a plumber if possible. They are expensive.