Its so annoying to hear your toilet constantly running. Not only that, it cost you money in your water bill. Its a very simple problem to solve and is probably not necessary to call in a plumber. You can buy a flush kit at the local hardware store. After turning off the water to the toilet and getting the tank try, you will need to remove all the old parts. Then by following the instructions in this video you can replace the old parts with the new. No more running toilet.