I have PVC pipes under my kitchen sink and the draining water is leaking out where the pipes are put together. What should I do?

First try to tighten the joints with hand. 1/4 turn should do. If not, use channel locks. Give it another 1/4 turn. If they continue to leak then you may have to replace plastic washers located under each plastic nut. Also, make sure all pipes are aligned on each other.