My bathroom sink was draining very slow. It would fill up while washing your hands and drain over the next few minutes. Today, I took the drain (trap and PVC to the wall) apart, cleaned it all out, and found no blockage. A bit of build-up, but no blockage.
When I put it back together again, I tightened all the connectors (the drain goes from the drain attached to the sink > extender > trap > extender > drain pipe sticking out of the wall), and then turned the water on. It didn't drain at all. It was no longer slow to drain, now it wasn't draining water at all.
Thus, I started to take the drain back apart to see if I messed up something obvious. As soon as I adequately unscrewed one of the connectors, the whole sink drained (remarkably fast I might add). I maneuvered the drain some, thinking maybe the way I attached the various extenders/trap was causing some sort of bad angle (although I couldn't see how), and tightened everything back down.
Again, I turned the water on, and again the drain didn't drain anything. Again, I loosened one of the connectors, and again, the whole sink drained immediately.
So ... with my extremely limited understanding of plumbing, I can only think the drain is having the same issue as when you take a straw, put it in liquid, put your finger over the top of the straw, and then remove it from the liquid. The liquid won't drain from the straw until you remove your finger, and the bathroom sink drain won't drain until there's somewhere for the air to go ... maybe?
This doesn't make sense to me, but plumbing is very much not my strong suit. Does this make sense to anyone? Am I missing something obvious here?
Thanks in advance!