Hi. Water from my bathroom sink takes a long time to drain. Recently I have been using Buster or an own brand sink unblocker-I leave the unblocker to work overnight, and then pour boiling water down. For that one day after using the unblocker, the water runs out of the sink fine. It then goes back to draining slowly. I am the only one to shave in the house, and I use a shaving cream, rather than foam so I don't think it's got anything to do with what I'm putting down there. What should I do? Thanks.
