Sewage backup into the home is one possible sign of a failing system. However, backup can also be simply the result of a blockage somewhere between the house and the septic tank (this is relatively easy to fix). Another possible sign of failure is a smell of sewage outside the house. If this smell is more noticeable after a lot of water has been put into the system – multiple showers or several loads of laundry (if the laundry waste discharges into the septic system), for example – this may be an indication that the leach field is failing. The smell may also be accompanied by a “spongy” feeling in some areas of the leach field, near the distribution box, or near the septic tank. The “spongy” feel may be caused by water and waste being pushed to or near ground level. If ponding water is also seen, this is called “breakthrough” and is an almost positive indication of failure of one or more parts of the system. This smell, however, can also originate at the plumbing vent. In either case, further investigation is warranted.
If you see such signs, a dye test may confirm your suspicions. For this test, a special strong dye is put in the system – usually by flushing it down the toilet. A significant amount of water is then washed into the system. If there is “breakthrough”, the dye will become visible on the ground surface. If the dye is seen on the surface, this would be a very strong indication that the system has failed. Your Home Inspector, a licensed professional engineer, or a septic system contractor can usually perform this test for you if it is needed.