First time poster here, completely clueless homeowner trying to avoid calling a plumber. I took apart our bathroom sink plumbing because it wasn't draining. The clog was below the stopper valve so I ended up taking off the tailpiece and the P trap. Everything is cleaned out and put back together, but there's still a slight problem. Soapy water leaks out of the joint between the tailpiece and the P trap. Soapy water only - pure water runs through without a problem. I've checked the gasket and it appears to be facing the right direction (tapering into the P trap). Do I simply need a new gasket or have I made another mistake? There also seems to be a slight drip between the top of the tailpiece and the drain pipe.