There's never a good instance when store-bought chemicals are better for a clog than hiring a professional. The primary concerns about using chemicals are that it eats away at your plumbing and is bad for the environment. However, it's also important to understand that a serious plumbing problem can go undiagnosed because chemical drain cleaners mask the symptoms; your drain may seem temporarily fixed, but you won't know for a while that you have tree root intrusion that's only getting worse.