Please choose the correct ending to complete the given sentence: Home and Garden: [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.

Ending1: Instead of using chemical drain cleaners, you can also purchase chemical drain cleaners at your local hardware store. [substeps] Begin by filling your drain about halfway with warm water. Ending2: Plastic or wood drain cleaners can cause thick, stubborn fluid to build up in a drain. If you are unable to resolve the problem yourself, get a professional to. Ending3: [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. Ending4: Installation instructions are similar to those of conventional drain cleaners, but differ slightly from that used in traditional plumbing systems. [substeps] Run water or a hose through the drain at the bottom of the pipe.

Answer format: ending1/ending2/ending3/ending4