Chemical drain cleaners do work, depending on the type of clog you have and how tough it is. Chemical drain cleaners work by creating a chemical reaction in your pipes.
When using chemical drain cleaners, always make sure to choose the right type of cleaner for the job. Also, make sure you know what kind of pipes you have, and how old they are so you can avoid using any chemical drain cleaner that might damage your pipes. Older pipes can become damaged due to the chemical reaction created by chemical drain cleaners. This can lead to bigger issues, like leaking pipes, and the need for plumbing repair services.
To avoid damage, physical methods are always best. Plunging or snaking a drain will ensure that it is not damaged by chemicals. When in doubt, call a drain cleaning plumber for professional advice and assistance.