There are several signs that indicate your septic tank could be full. These include standing water over your septic tank, a strong odor coming from your yard, gurgling water, slow drains, or a sewage backup. While many of these signs could also be indicative of a clogged system, they should all be checked out by a professional ASAP to avoid costly damages. In the absence of any of these signs, it’s recommended that septic tanks be emptied every 3 to 5 years on average.