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How often should you pump?

a typical residential septic system

Septic systems last longer if they are pumped regularly. Bacteria convert most of the solids to liquids, but some solids remain. If the solids fill the tank, the field lines will clog, and the system will need replacement. Preventative maintenance is cheaper then necessary repairs. A common myth is that septic tanks systems last forever, but DHEC reports that 10 to 30 percent of septic systems fail every year. Regular pumping is critical to the life of a system.

Just as changing your oil doesn't fix a broken engine, pumping will not fix a broken septic system. Often by the time the problem is discovered, pumping is not the solution. Pumping is a maintenance procedure, and we recommended at least every Three Years.

DHEC has a timing chart for pumping: DHEC Septic System Maintenance Brochure.pdf , but the chart below goes into more detail.

See the table below based on the research of Penn State University. Look up your tank size and number of building occupants to see how often the septic tank should be cleaned.

Table I. Septic Tank Pumping Frequency in Years
.Household size - Number of Occupants
.1 2 3 4 5 6 7 8 9 10
Tank-GallonsSeptic Tank Pumping Frequency in Years
500* 5.82.61.51.00.70.40.30.20.1--
750* 9.14.22.61.81.31.00.70.60.40.3
900 11.05.23.32.31.71.31.00.80.70.5
100012.45.93.72.62.01.51.21.00.80.7
125015.67.54.83.42.62.01.71.41.21.0
150018.99.15.94.23.32.62.11.81.51.3
175022.110.76.95.03.93.12.62.21.91.6
200025.412.48.05.94.53.73.12.62.22.0
225028.614.09.16.75.24.23.53.02.62.3
250030.915.610.27.55.94.84.03.53.02.6


NOTES to the Septic Tank Pumping Schedule Table:

  • Numbers in the septic pumping table indicate septic treatment tank pump out in frequency of every nn years for conventional septic tanks, and assuming for year-round occupancy of the residence. (This data does not pertain to simple holding tanks which retain all solid and liquid waste with no treatment no effluent disposal system.)
  • * These septic tank sizes are below the minimum size allowed in Pennsylvania and other jurisdictions. Florida septic tank pumping rules and Ohio septic tank cleaning rules may be more demanding.
  • Minimum septic tank sizes: Under current Pennsylvania law a 900 gallon septic tank is the minimum size that must be used for a home with three bedrooms or less. If six people reside in a three-bedroom house, the tank should be pumped every 1.3 years. If the same system serves a family of two, the tank would be ready for pumping every 5.2 years. Systems installed before the current rules and regulations were implemented may need to be pumped more often, perhaps every year or less.
  • Garbage disposers will increase the frequency of pumping. For example, if this same three bedroom house with six residents had a garbage disposal and was generally producing a higher volume of wastewater, the pumping frequency would be calculated as follows: 1.3 years - [(0.2) x 1.3 years] = 1.0 year.
  • Onsite sewage disposal system holding tanks, where there is no septic field, will need to be pumped more frequently based simply on the rate and volume of septic waste inflow.

We have edited and added to the original septic tank pumping guideline material based on research and field experience testing, inspecting, and installing septic systems and based on study of other reference sources on septic system maintenance and design.

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