The answer to 'how to fix septic tank' is to regularly maintain and inspect your septic system. This includes having a professional pump out and inspect your septic tank every 3-5 years, depending on the size of your household and tank. Additionally, you should avoid flushing non-biodegradable items, limit water usage, and ensure the drain field is clear of obstructions.
If you notice any issues like slow draining, foul odors, or sewage backups, it's important to address them promptly to prevent further damage. In some cases, you may need to have the septic tank repaired or replaced by a licensed professional.