The hex nut in a toilet is what keeps it tightened down on the flange. Most of the time you will not experience any problems with the hex nut itself. A lot of times when a toilet is leaking, it is within the flange or seal. However, the hex nut can cause a leak if it is not tightened enough onto the flange. Here is how you can fix this easily with a few tools.
Step 1 - Tighten Hex Nuts
The easiest fix is to simply tighten the hex nuts. If the nuts are warped or damaged, they will not be able to be tightened. Use a wrench or pair of pliers to tighten them down. If the leak continues, replace the nuts.
Step 2 - Remove Damaged Hex Nut
Using a pair of pliers, loosen the hex nut and remove it from the flange bolt. Remove the washer also. Many times, the washer is the cause of the nut not being able to be tightened.
Step 3 - Install New Hex Nut
With the old hardware removed, set the new plastic washer on the flange bolt. Screw the nut onto the bolt and tighten it with your fingers. Use the pliers to tighten it a few more turns and check for any leaks.