A Guide to Septic Cleaning
How Often Do You Pump Out A Septic Tank?
The table shown below lists the recommended septic tank pumping frequency according to septic tank capacity and household size. The frequencies were calculated to provide a minimum of 24 hours of wastewater retention assuming 50 percent digestion of the retained solids.
Common septic tank pumping frequency mistakes
- Failure to pump the septic tank frequently enough: leading to an early drainfield failure and costly repairs
- Pumping or cleaning the septic tank too frequently, wasting money (though you’re wasting a lot less money than the cost of a new drainfield.Some septic pumping contractors and some other “experts” give a fixed rule of thumb that serves their own interest, such as “pump your septic tank every year” or “pump your septic tank every two years” or in a case we know about in Minnesota, “pump the septic tank every couple of months or after you’ve had a lot of visitors”.
It would be smarter to pump the septic tank before or both before and after heavy use if we know the septic system is marginal. Pump the tank before a period of heavy usage to avoid a sewage backup during the heavy usage interval and afterwards to get back to normal usage levels.
Contractors may give this advice without first having actually considered any information about the septic system capacity, level of usage, age, or other conditions. It’s a great example of “OPM” or “other people’s money” – spending someone else’s money to reduce your risk that they’ll complain that your advice wasn’t safe enough.
- Pumping the septic tank with the fantasy that doing so will “fix” a clogged or failed drainfield. All you really gain is a few days of toilet flushing before the tank has re-filled.
Actually inspecting the septic system, diagnosing any problems or failures, and inspecting conditions inside the septic tank will tell us whether the tank is being pumped at the correct frequency.
The removal of septic waste by cleaning the septic tank is a critical step in septic system care as it extends the life of the septic field. Even if you don’t care how septic systems work you need to know when to clean the septic tank by pumping out septic waste. Using the septic tank cleaning frequency table just below, simply look up your tank size and number of building occupants to see how often the septic tank should be cleaned. Later in this article we list other factors that can increase or decrease the recommended pumping rate.
Table I. Septic Tank Pumping Frequency in Years
|Septic Tank Size
|Household size – Number of Occupants|
Septic Tank Pumping Frequency in Years
NOTES to the Septic Tank Pumping Schedule Table: