Things You'll Need
Sand or gravel
How to Fill a Septic Tank. Many people have chosen to stop using their existing septic system and tie into the public sewers. Once their septic tanks have been pumped out and are no longer being used, it is up to the owner to dispose of the tank. Many areas allow you to leave the tank in the ground instead of removing it, but it must be filled in for safety reasons.
Check with your local municipality or health department to see if a permit is required to fill in your old septic tank.
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Rent or buy a water pump from your local hardware store. Old tanks have probably collected water and debris that needs to be cleared.
Pump out any standing water in your septic tank. All waste should already have been pumped out prior to the start of your project, so the water in the tank should only be rain or ground water.
Drill holes or otherwise puncture the bottom and sides of the tank. This allows any water that will eventually makes its way back into the tank, an escape.
Fill the tank with sand or gravel. The sand and gravel allows water to filter through and also fills in the void in case the tank would eventually collapse.
Septic tanks should be pumped out by a septic system pumper before attempting to fill in your tank. You may want to call a local septic system company to see if they offer septic tank filling as a service. They may also have filling guidelines on hand, as well.