Bathroom Sink Fills Up and THEN Drains Rapidly
Bought this used house about 2.5 years ago. Bathroom was remodeled within the last 10 years by previous owner.
When we open the faucet of the bathroom vanity sink, with the faucet fully open (i.e., water coming out fairly quickly, which is how I typically use it to brush teeth or wash hands), the sink basin fills up and the water doesn't seem to drain (it probably does, but very slowly?). Then, after a minute of the sink being full and the water still running, all of a sudden the sink drains really fast, as if a blockage/lever were released somewhere.
This has been happening ever since we bought the house. I've cleaned the drain and also took the trap off a year or so ago and checked to see if any debris was in it but it was clear.
What is causing this?