There are a few signs you should get a new septic tank. These include the following: Unpleasant odors: If you smell sewage, you may be dealing with an overfilled septic tank that's solid waste.  Standing water: If there's no obvious cause for standing water like heavy rainfall, you may have an oversaturated drain field or a broken pipe or septic system. Slow draining: A full septic tank will cause pipes to drain more slowly.  Patches of vibrant grass: A wastewater leak can actually fertilize grass, making it grow thicker and greener over your septic area.  Home addition: Building onto your house or adding more residents will affect the septic system. Make sure your septic tank can handle any additions.  Nearby water contamination: A septic tank leak can lead to wastewater contamination that can deposit nitrate, nitrite, or coliform bacteria in water sources near your home. If these bacteria are found nearby, check your septic system to see if it's the source. Old age: If your septic tank is at the end of its life span, it's time for a new one.