I need some help with a blocked sink. I moved in and the sink was blocked, I have tried drain unblocker and using a snake and couldn't find any blockage. There is a gurgling coming from the sink after water goes down sometimes and if I loosen the seal on one of the pipes the water flows much better so I think it's a problem with airflow. Can you please let me know if this could be the problem and any steps I can take to solve it?
