Plumbing – How to stop sink from dripping/leaking

It appears from the video the sink bottom connection is assembled wrong. From top to bottom you should have sink, rubber gasket, metal flat washer, brass nut. This or the P-trap connection do not need to be super tight, firmly snug should be enough. If the connections leak when snug, the gasket or sealing ring is likely damaged, or possibly their mating surfaces are not clean and smooth.

More disturbing is you say drain/popup detached from the sink when you were fussing with the P-trap? This should not be possible. If it did happen, the drain/popup is broken and needs to be replaced. This is not something you could have done alone, it was ready to break anyway. The flange you see when standing over the sink is part of this assembly, the large nut underneath sort of clamps the sink between the rubber gasket and this flange. The drain/popup is normally installed by dropping it in from above. If it came out from the bottom it is broken.

I know that you said you cannot get the cleanout plug - but this is your best bet at removing large debris.

Try:

• Wrap a small towel over the plug and turn counter clock wise ("Righty tighty, lefty loosy")

• Use an adjustable wrench to break the cleanout plug free

If the above attempts do not work or you have already done that route:

• Use a drain snake to free any debris causing the clog
• You can use a toilet plunger by placing it directly above the drain in the sink, fill the sink until there is enough to create suction; (be careful not to splash too much)
• Believe it or not, if a graden hose is accessible and long enough to reach the sink, place the hose in the drain and have someone turn on the water. There will be sufficient pressure to dislodge any debris.

I'm not a fan of using drain products, but if you must, go to your local hardware store and consult someone as this community covers the entire globe, it is difficult to give you an exact recommendation.