The most common septic mistake is if you aren’t having any problems, you don’t need to pump your tank. Scheduling regular maintenance is the most important thing a person can do for their septic tank. As you use your system, solids settle to the bottom as sludge, while the lightweight materials float as scum. Regular pumping prevents solids from escaping into the drainfield and clogging up the soil. A regular used septic tank should be pumped once every 3 years on average. If you have a garbage disposal, you should pump sooner.