OTC drain cleaners come in various forms: powder, gel, and/or liquid, the common denominator is the chemicals. Drain cleaners use a chemical reaction to break down the source by either adding or removing electrons to the clog, this reaction typically generates heat, which can damage pipes. OTC drain cleaners basically come in 3 types.
CAUSTIC – Lye and a caustic potash are the significant ingredients with these cleaners. Caustic cleaners give electrons to the clog in an attempt to clear it. Other chemicals involved release heat trying to turn a grease clog into a soapy substance that can be dissolved. Caustic cleaners are heavier than water, so they will sink past the backed up water to reach the clog.
ACID – This type of cleaner is often sold only to licensed plumbers. They contain hydrochloric & sulfuric acids that pull the electrons from the clog. The reaction will generate heat in order to melt or soften the stiff mass buildup. An issue with acid based cleaners is they can damage pipes, especially older ones.
OXIDIZING – Ingredients like bleach, nitrates and peroxides compile the oxidizing drain cleaners. They pull the electrons from the clog to initiate oxidation. These chemicals are also heavier than water, so reaching the clog is easier and more effective.
Other than pipe damage, OTC drain cleaners are toxic and cause issues with your skin and eyes. Chemical drain cleaners may also release dangerous fumes and have been used as an explosive in some instances. They can damage the eco system inside your septic tank as well as permanently discoloring some faucets.
Always follow the directions and never mix one OTC drain cleaner with another.