fourth year
Since it will not work, don’t bother. And once it is in the drain, if the pipe is completely plugged, a plumber is going to be put in a hazardous situation, not to mention possible damage to his equipment, trying to unplug the drain. If you have to use anything, stay with the commercial drain cleaners. They also do not usually work, but they are at least diluted enough so that the plumber can work through them.
