What is the most effective drain cleaner for septic systems?

The most effective drain cleaner for septic systems is one that is specifically labeled as safe for septic systems, such as a bacterial or enzyme-based cleaner. These cleaners are designed to break down organic matter without harming the beneficial bacteria in the septic tank. It is important to avoid using harsh chemical drain cleaners in septic systems, as they can disrupt the balance of bacteria and cause damage to the system.