Tighten the packing nut on the toilet shutoff valve one-eighth turn clockwise to try to seal a leak around the nut. Pro tip: Wrap cloth or masking tape on the plier’s jaws to protect the nut’s finish.

Some plumbing problems definitely call for pro-grade expertise, but fixing a water shut-off valve leak isn’t one of them. Here, we aren’t talking about leaking from the connection between the valve ...