Septic Tank Pumping Table - When to Clean the Septic Tank

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Septic tank cleaning or pumpout frequency guidelines or rules:

This article provides a septic tank pumping schedule based on septic tank size and level of usage. This document explains a key point in how septic systems work: the septic tank & septic system cleaning schedule - when to pump out the septic tank.

We describe all of the reasonable methods for determining the recommended frequency for cleaning out a septic tank: using a cleanout frequency table, using objective measurements, using an electronic tank monitor. We also explain what is septic tank effluent retention time, why to measure septic tank scum and sludge levels in sum we provide a comprehensive guide to answering: How often should septic tanks be pumped?

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

SEPTIC TANK PUMPING SCHEDULE - A Guide to Septic Cleaning - How Often Do You Pump Out A Septic Tank?

Septi tank cleanout started (C) Daniel Friedman TABLE # 1 given just below lists the recommended septic tank pumping frequency according to septic tank capacity and household size.

The septic tank pumping schedules given here were calculated based on basic septic system design concepts requiring a septic tank to provide a minimum of 24 hours of wastewater retention assuming 50 percent digestion of the retained solids.

Common septic tank pumping frequency mistakes

  1. Failure to pump the septic tank frequently enough: leading to an early drainfield failure and costly repairs
  2. 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.

    See SEPTIC BACKUP PREVENTION for tips to avoid a septic problem during times of anticipated heavy septic system usage.

    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.
  3. 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.

See this complete list SEPTIC TANK PUMPING MISTAKES and fantasies about how septic tanks work and how they should be maintained.

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 

Gallons / Liters

Household size - Number of Occupants
1 2 3 4 5 6 7 8 9 10

Septic Tank Pumping Frequency in Years

500 gallons * / 1890 liters
750 * / 2840
900 / 3400
1000 / 380012.
1250 / 500015.
1500 / 550018.
1750 / 650022.
2000 / 750025.412.
2250 / 850028.614.
2500 / 9500 30.9 15.6 10.2 7.5 5.9 4.8 4.0 3.5 3.0 2.6

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. For more analysis of the effect of garbage disposers on septic systems

  • Typical Septic Tank Pumping Costs: A typical fee to pump a septic tank is $200. to $300 to pump a septic tank up to 1000g in size, provided that the tank pumping access port has been uncovered and is readily accessible.

    If the septic pumping contractor needs to find the septic tank and then excavate the septic tank pumping access opening, expect to pay an additional $350. to $400. provided that no extraordinary measures are needed. Prices vary somewhat by region. A part of the fee you're paying your septic pumping contractor is the cost to dispose of the septage.
  • For an explanation of the meaning of sewage levels in the septic tank and how that information informs septic tank pumping frequency,

  • Portions of this information were provided by the Penn State College of Agriculture - Cooperative Extension. 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.

Septic Tank Pumping Schedule for Part-Time Occupied Buildings

Question: What Schedule should I use to Pump a Part-Time-Occupied Summer Home?

22 Sept 2015 Bill said:

I have a camp with a 1250 gal. tank. It is seasonal, only used in the summer. We have shower, toilet and sink that empties in the septic. What schedule should I use to pump?

Reply: Divide the Septic Pumping Table Frequency by the Portion of Year of Building Occupancy

Bill you can take any point in the septic pumping schedule table and then increase the length of the interval between septic tank pumpouts by making this reasonable-guess:

1. Choose the number of building occupants to find the proper line in the pumping shcedule. Also choose the table entry for the size of your septic tank in gallons.

2. Choose the number of months during a year that the building is occupied

3. Calculate the new pumping schedule by dividing the number in the table on this page by the fraction of the year that the building is occupied.


Household size = 4 people
Septic Tank size = 1250 gallons
Table pumping frequency: every 3.4 years (Keep in mind it would be ridiculous to think that we can know precisely the conditions in an individual septic tank - these are general guidelines)

3.4 x 12 = 40 months between tank pumpings

Months your Camp is occupied = 4

Months in a year = 12

Portion of the year your camp is occupied = 6/12 = .5 or 50%

Pumpout Schedule from Table / Portion of Year Occupied = 40 months / .5 = 80 months between pumpouts.

Watch out: before launching into an extended we-don't-have-to-pump-the-septic-tank-because-InspectApedia-said-so interval, it would be smart to have your septic tank pumped and its condition inspected so that you are starting from a known condition. Whenever you open and clean a septic tank the following can give a more accurate idea of the actual septic tank pumping frequency needed at a specific building:

Watch out: for any building that sees occasional surges of heavy septic tank use, simply pumping the tank based on average occupancy over the year can get you into trouble. The big surge of sewage and wastewater can overwhelm the septic system's ability to cope, particularly you may flood the drainfield or push solids into the soakbed, drainfield, or seepage bed.

You might head off trouble by pumping the septic tank out completely just before the surge of visitors. A sewage backup into the building or out onto the ground during a wedding can be a nasty touch to an othewise lovely event.

See SEPTIC TANK PUMPING REASONSwhere we describe pumping the septic tank before a par;ty.


Pumping Schedule for Sewage Holding Tanks

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.

A smart design for sewage or septic holding tanks is the inclusion of a septic tank alarm system that will tell when the tank needs to be pumped. Set the alarm float to sound the alarm early enough that you can continue to use the plumbing system while waiting for your septic pumping contractor to arrive.


A periodic inspection of the septic holding tank levels is an alternative but not one that most people actually manage to follow with enough care to avoid trouble.

Electronic Monitors for Septic Tank Scum & Sludge Levels Give Septic Tank Cleanout Frequency

Septic tank monitor

Below at References we also describe an electronic septic tank monitor or grease trap monitor from Worldstone.

These devices can track sludge, scum, or grease levels in order to best schedule septic tank pumping or grease trap cleaning. This product is suitable for commercial installations and possibly for some residential septic tank systems.

According to the company, "Data from monitors can help establish appropriate service intervals, and document maintenance for regulatory compliance. Alarm features can help detect abnormal conditions and prevent costly backups."The company also produces an oil tank level monitor.

Thanks to reader Robert Shirley for this tip.

OPINION - DF: this product is a great idea for commercial installations or problem septic installations. Substituting actual septic tank scum layer thickness or scum level thickness data for the septic tank pumping schedule table above may allow the tank to be opened and pumped less often - saving some money.

Watch out: But don't forget that regular opening and inspection of the septic tank, such as happens when the septic tank is to be pumped out or "cleaned", gives an additional opportunity to check for other septic system problems that could be leading to a costly failure, but that don't directly concern the septic tank sludge or scum layer thickness.

Examples include the discovery of lost or damaged septic tank baffles, septic tanks leaks that allow ground water to flood the septic system, or septic tank leaks out of the tank.

Alternative Septic Tank Pumping Frequency Guidelines: the University of Minnesota Septic Tank Inspection Frequency Point System

The University of Minnesota has published "Septic Tank Pumping Frequency Guidelines" that take a different approach than the cookbook table of septic tank sizes and number of building occupants shown in our table above.

But the document does not really tell the homeowner when to pump the septic tank. Instead it calls for essentially very frequent septic tank "inspections" to decide if pumping is needed, without, regrettably, explaining what that inspection would entail nor how that inspection would decide that the septic tank needs to be cleaned.

Watch out: In sum, we cannot recommend this chart's use as the best or sole option for deciding when to pump out a septic tank, nor does the chart actually answer that question, as we explain below.

However it would indeed be a "safe" approach to inspect the septic tank conditions at every one, two, or three years, which is the actual end result of this misnamed worksheet.

Septic Tank Pumping Frequency vs Septic Inspection Frequency - clarified

Instead of taking the widely-used septic tank size and number of bedrooms table approach, U.Minn. experts have provided a table or questionnaire that when answered, gives a septic tank inspection frequency in years.

The appeal of this approach is that it allows a homeowner to take into consideration factors that would either increase or decrease the interval for septic tank inspection based on factors that increase or decrease the septic failure risks posed by the home and its usage. Unfortunately factors enumerated in the point-counting approach have some troubles of their own, as we explain below.

The added cost of annual to tri annual septic tank inspections might be weighed against the safety, fine-tuning, and "actual septic tank data" approach to septic tank inspection frequency we describe below, or the simple and easy to use septic tank pumping frequency table we provided above.

Watch out: the septic tank worksheet does list some interesting septic tank risk factors, as we elaborate below. However, overall the worksheet we reviewed underweights the septic tank failure risk of some factors and overweights or confuses others, and it does not directly address the risk of drainfield damage caused by flushing high volumes of wastewater (laundry, water softener) through the septic tank.

But the chart doesn't do that anyway. Although the chart's title is "Septic Tank Pumping Frequency Guidelines" it does not provide that information. Instead, if you complete all of the work and analysis in this chart, you end up at one of three frequencies at which you should inspect the septic tank condition to determine if it needs to be cleaned:

Septic System Failure Risk Level Factors vs Recommended Inspection & Pumping Frequency
Septic Worksheet Risk "score"  
0-8 = Low Risk

2-3 year septic tank inspections:

Evaluate the septic tank conditions every 2-3 years to see if cleaning is needed.

In Minnesota some municipalities require septic pumping or inspection every 3 years.

Requirements vary in other U.S. States & Canadian Provinces as well as of course municipalities in other countries.

8 - 18 = Medium Risk

1.5 - 2.5 year septic tank inspections:

Evaluate the septic tank conditions every 1 1/2 - 2 1/2 years to see if cleaning is needed

19-26 = High Risk Annual septic tank inspections: Evaluate the septic tank every year to see if cleaning is needed

Adapted from the U. Minnesota septic tank pumping frequency worksheet cited below at reference [5]

[5] "University of Minnesota Septic Tank Pumping Frequency Guidelines", University of Minnesota, 2009 for extra copies of the original chart call (800) 322-8642, retrieved 1/15/2010, original source:
@ostp/documents/asset/cfans_asset_126408.pdf [copy on file as U_Minn_Septic_Pumping_Chart.pdf]

U.Minn assigns a numeric value such as 0, 1, or 2 or for some items 0-4 as the septic system load is likely to be increased. The homeowner adds up various risk number totals to reach a "risk score" that puts their system into one of three categories of septic tank "evaluation" frequency. "Evaluation of the septic tank " here means determine if it needs to be cleaned.

Do We Need to Evaluate the Septic Tank ?

Really? What the heck does "Evaluate the Septic Tank" mean? This question is not addressed in the UM worksheet. Without septic tank inspection points, pass/fail criteria, or trouble signs for which the "evaluator" is to be alert, we just don't know what to make of this advice and we certainly can't expect any consistency in the results.

However we answer this question in excruciating detail beginning at SEPTIC TANK INSPECTION PROCEDURE where we list many things that should be evaluated to avoid septic system failures or worse, unsafe conditions; or you can "cut to the chase" as mom says, and have your septic contractor open the septic tank and MEASURE SCUM & SLUDGE, to know objectively if the tank needs pumping.

Watch out: "Evaluation of septic tank condition" is not well defined. Experts generally agree that there are a number of inspection points including the septic tank sludge and scum layer thickness that determine that septic tank pumping is needed (or not) but that there are other inspection points that are very important such as evidence of backup, damaged baffles, tank flooding or septic tank leaks, and of course septic tank safety: safe covers, no signs of collapse risk, etc.

Some Factors that Should Increase the Septic Tank Pumping Frequency

If you don't know where the septic tank is located, see SEPTIC TANK, HOW TO FIND.

At TANK INSPECTION PROCEDURE we describe how to inspect the septic tank before, during, and after tank cleaning operations.


Continue reading at SEPTIC TANK PUMPING SCHEDULE FAQs or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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Septic Tank Pumping Articles

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