Septic Tanks should be pumped out every 3 to 5 years depending on how often the septic tank is used.
You can use Rid x to help break down solids in the septic tank as well but still you need to pump it out every 3 to 5 years.
If it's been 5 years since the last time the septic tank was pumped then it's a good idea to get the septic tanked pumped.
Some signs that your septic tank is full and needs pumped are sewage backup, slow drains, pooling water, odors or a really green lawn where the septic tank is located.
Another sign that your septic tank is full and needs pumped is A toilet that reacts slowly when you flush it, (gurgles, slowly drains etc.) then it may be an indication that your septic system is too full and needs to be pumped out.