Used the P traps available at my local HW store. Great fit on one, the other seemed to be missing the correct flange. Bought another. Installed and constant micro lesks. These leaks are where the down spout meet the top of the p trap. My q is... is the angle of the drainage pipe to blame, or the gasket. In my opinion it should never leak this high (3" above the junction) . I just had a single sink line converted to a double, the plumber did the work with in the drywall, I did everything else.
It shouldn’t leak .. take apart , and try pipe dope or Teflon tape on threads .. Edit: take picture and post
If it is this style, either PVC or "metal" then there should be a gasket, no dope or tape needed. If the gaskets are in good shape and everything else matches try to run a sink full of really hot water thru it then snug the connections up. I suppose you should also make sure there are no down stream obstructions restricting flow as well. Edit to add... It seems obvious but make sure the tailpiece extends far enough into the P-trap so the gasket seats properly.
These come in 1.25 and 1.5 inch diameters. All connections have silicone or rubber gaskets, make sure they are in place. Make sure you are mating like to like. There are also adapters if needed.
And make sure the ring gaskets are in right side up. Flat edge up, and sharp edge pointed into the trap...
Compression gaskets. Make sure right side up as mentioned and hand tight plus 1/4 turn after hot water is all you need. Pipe needs to be CLEAN Tape and dope is useless on those.
Look for a local plumbing supply house. MUCH higher quality for similar prices. Don't trust your tape job to last.