Neither Drain-o or Liquid Plumber really solves the problem. All they do is blow out the weakest part of the clog. Each time you run waste water down the drain, organic matter goes down. Over time, this stuff sticks to the walls of the pipes, restricting water flow. As time continues to pass, this mass grows by trapping more matter each time the drain is used. The drain begins to run noticeably slower, because this gunk is forming all along the inside of the pipe, reducing the diameter of the water channel. Finally, it stops up all together and becomes a clog. Try using a product called Drain Care. It is made of dry, powdered enzymes. You mix it in warm water, like instant coffee. Pour it down the drain and let it sit. The enzymes actually eat the organic matter up and down the drain pipe. With repeated use, you will have nice clean drains. It is non-toxic, harmless to all types of plumbing, and actually assists septic systems.