2nd post. Blocked bathroom sink seems clear to stack and beyond.?

If it is clear at the stack, it can only be in 1 of 3 places. First is it may be blocked at the "T" fitting behind the wall inside the cabinet. Second may be in the "P-trap" itself. Third may be in the drain tube directly under the sink. My suggestion is to remove the P-trap completely and clean that out. Next inspect (from inside the cabinet looking upward) through the drain tube, and clean that out. Third clean out the waste line at the 1 1/2" T fitting behind the wall. The last one may require to be snaked out if it is the actual problem.

it is unlikely but possible. Get a small "drain-king" 1"- 2-1/2" range rubber inflatable drain tool connect water. remove "p" trap unde sink in question. connect to water let inflate to inside pipe and then tun on full. The pressure should purge the leak. try this save you $200-275. from a retail plumbing company repair bill

if your sink is backing up, the most likley cause is that the p-trap under the sink is blocked up and needs to be cleaned. If that's not it, the drain line below the sink, where it goes into the wall needs to be snaked from that point, down.

Hire a plumber before this turns into a serious problem.