There are many issues to identify in a septic tank failure. They include: the drainfield failing because the tank was not pumped often enough, clogging in such a way that the drainfield muck prevents the soil from absorbing water, and excess sludge build-up that prevents breakdown of substances. In such cases, you may have to consult your plumber about setting up a new drainfield.
Replacing a septic tank comes with its own challenges. For example, state sewage management regulations mandate that new septic tanks cannot be installed within 50 feet of active wells, within 25 feet of natural bodies of water, and no closer than 10 feet from the property line. Local health and environmental authorities should also approve the operation.