This spray is famous for its versatility, and yes, it does soften lime deposits, but you don’t need to boil it or flush it down the overflow tube. Just spray it all around under the rim and wipe it after some time. If you opt for WD-40 because of its reputation, you can purchase a can with a flexible straw that perfectly suits cleaning toilet jet holes (EZ-Reach). Use it to clean the jets or to reach under the rim bend.