sink strainer

One of the strainers in my kitchen sink (the side without the garbage disposal) started leaking in the putty/gasket area. After seeing a bunch of videos about how to replace it, I attempted to do the same. However, while all videos talk about removing the lock nut and having that be the hardest...

I recently installed a new sink strainer and the day after, after maybe about 20 minutes of use, I noticed a slight trickle of water from that side of the sink. It look like it's coming from the seal, and perhaps the locking nut that connects the PVC pipe to the strainer. The locking nut isn't...