[header] How to unblock a drain [title] Use a chemical drain cleaner. [step] Using a chemical drain cleaner is one of the most common ways to unclog a drain. Always follow the manufacturer's instructions when using chemical drain cleaners. 
[substeps] Make sure you buy a drain cleaner that is compatible with your system. If you have a septic tank, you will need to find drain cleaner that is suitable for septic systems.