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Septic Tank Pumping Procedure - When to Pump Out Septic Tanks InspectAPedia®  -     How to pump out / clean a septic tank, step by step photo-illustrated guide Before starting, some safety warnings for septic pumpers and homeowners When to pump the septic tank - why now? How to find the septic tank How to open the septic tank cover; removing the septic tank cover How to Inspect before pumping the septic tank; How the pumper truck or vacuum truck is operated Actually pumping out the septic tank; septic tank inspections while pumping Washing the septic tank after pumping, inspecting the tank after pumping Closing the septic tank How to record the septic tank location, advising homeowners

This document provides a step by step, photo-illustrated guide to opening, pumping, and inspecting septic tanks, how a conventional septic tank is located, opened, pumped out, cleaned, and inspected. This guideline is intended for septic pumping tank truck operators and as general information for homeowners or septic service companies concerned with septic system care.

Readers should see Septic Tank Pumping Frequency Guide for a table explaining when to schedule a septic cleanout. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical reviewers are welcome and are listed at "References."

This is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

A Photographic Guide to Pumping a Septic Tank

How to Determine If and When a Septic Tank Needs to Be Pumped

Pump the septic tank based on usage level - using the septic tank pumping tables

The most common method used to determine when a septic tank should be pumped is to use a tank pumping frequency table which suggests the tank cleanout interval as a function of tank size and the level of usage of the system, such as the number of occupants in the building.

We provide a table to give a septic pumping schedule at Septic Tank Pumping Frequency Guide. Refer to the table to see the recommended pumping frequency for the particular septic system being considered. For example, (from the septic tank pumping table), a 1000 gallon septic tank serving a home with five occupants should be cleaned out about every two years. If the tank has only a 500 gallon capacity, it needs to be cleaned about every six months!

Why a septic tank pumping table may be wrong - other septic tank pumping schedules

Septic tank shape affects its pumping needs.

What septic tank pumping tables may not recognize is the effect of tank shape on the need to pump it out. Most septic tanks are 4ft. to 6ft. deep. But if the tank in question is a "low boy" or shallow septic tank (used in areas where there is not enough soil depth to bury a conventional septic tank) it may need to be pumped more often.

Septic tank usage affects its pumping schedule.

Septic tank pumping tables presume a number of occupants based usually on the number of bedrooms in a home. If your home has more occupants or other reasons for heavier septic system use the tank needs to be pumped more often.

Use actual septic tank conditions to decide its next pump out time

By inspecting the conditions in the tank at pumping time you can decide if your septic tank should be pumped more or less often than called for in the pumping schedules.

Pump the tank based on sludge/scum thickness

The exact point at which a septic tank needs to be pumped could be determined by opening the septic tank and measuring the sludge and scum levels in the tank. As long as the sludge and scum layers are minimal (just a few inches of thickness) or in other words, as long a the "net free area" in the tank (see below) is adequate, the tank does not need to be pumped. (See "Septic Sludge & Scum Levels" and "Effluent Retention Time" links at "More Reading" below).

Depending on the size of the tank and its dimensions, as the sludge and scum layers become thick the net free area remaining in the tank becomes so small that there is inadequate time for solids to separate into sludge and scum layers. At this point, even though the septic system appears to be "working" its remaining life is in jeopardy because suspended solid waste is being pushed into the drain field.

The volume of net free area in a septic tank determines the time available for this solid and grease separation. That time is referred to as "septic effluent retention time." Short effluent retention time means that the tank sewage remains agitated which in turn means floating and suspended solids are being pushed into and thus are clogging the drain field.

Other reasons people pump septic tanks

There are other reasons besides time or sludge/scum layer thickness that lead people to pump septic tanks out. We list and discuss these in detail at Reasons For Pumping the Septic Tank.

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• Additional technical contributors & reference sources for this article are listed below.
• Special thanks to M & O Sanitation, Dutchess County NY (845) 471-0308 for permitting us to photograph steps during septic system service at our demonstration property.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website

• Special thanks to M & O Sanitation, Dutchess County NY (845) 471-0308 for permitting us to photograph steps during septic system service at our demonstration property.

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More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.


• Additives & Chemicals: Septic System Maintenance - Are they even needed? Are they even legal?
• Baffles, Septic Tank septic tank baffles defects and inspection suggestions
• Buyer's Guide Home Buyer's Guide to Septic Systems Inspection & Testing - What to Do, Step by Step.
• Cesspool failures (MA)
• Cesspool Safety Warnings include dangers of cave-in and fatality
• Cesspools Home Buyer's or Owner's Advice
• Clearances & Distances from septic system components to other site features, property boundaries, waterways, etc.
• Clogged Drain Diagnosis - is the problem the septic system or the Building drain system?
• Don't Flush these things into a septic system: a list of what's ok and what's not ok to put into septic tanks and building drains
• Drywells Home Buyer's or Owner's Advice
• Filters for Septic Tanks & Graywater to protect septic drainfields and reduce drainfield clogging
• SEPTIC FLOOD RESPONSE what to do after a septic system has been exposed to flooding
• Garbage Grinders and garbage disposal units - effects on septic systems
• Levels: Inspecting the Level of Accumulated Solids, Sludge and Floating Scum in Treatment Tanks - Measuring the Sludge and Scum Levels in Septic Tanks
• Liquid Level in the Absorption System - drain fields, seepage pits, galleys
• OUTSIDE SEPTIC INSPECTION - - Simple Visual Site Inspection Gives Key Information About Septic System Condition
• Retention Time in Septic Tanks Septic Tank Pumping Guide discusses retention time and "net free area" in a tank (allowing for sludge and scum layers)
• Septic & Cesspool Safety - septic system, septic tank, & cesspool safety warnings for septic inspectors, septic pumpers, and homeowners.
• Septic D-BOX Inspection provides for help in finding and inspecting the septic system drainfield distribution box
• Septic Sludge & Scum Levels in Septic Tanks - Measuring the Level of Accumulated Solids, Sludge and Floating Scum in Treatment Tanks
• Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Septic Tank Pumping Frequency Guide for Septic Tanks: When, How, What to Watch For when pumping or cleaning septic tanks
• Septic Tank Inspection Procedure - How to Inspect Septic Tanks and evaluate the septic tank condition, baffles, sludge levels, damage, evidence of septic failure, etc.
• Septic Tanks, Concrete defects and inspection suggestions for concrete septic tanks
• Septic Tanks, Fiberglass or Plastic defects and inspection suggestions for fiberglass or plastic septic tanks
• Septic Tanks, Home Made defects and inspection suggestions for home made or site built septic tanks
• Septic Tanks, Steel defects and inspection suggestions for steel septic tanks
• Septic Tank Sludge and Floating Scum: what makes up the contents of residential sewage
• Sewer Gas Odors diagnosing, finding, and curing septic tank and sewer line smells
• Sewer Gas - Methane and other septic system gas explosion or asphyxiation hazards such as hydrogen sulfide
• Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• Planting Over Septic Systems: trees, shrubs, groundcover over the septic system: what can you plant over or near septic system components without causing a problem?
• SPOTTING SEPTIC BREAKOUTS - Spotting Dyed Septic Effluent Breakout Outside - Where Septic Dye is Likely to Show Up During a Septic Dye
• When Not to Pump a Septic Tank to avoid damage, unsafe conditions, or wasting money

• Pennsylvania State Fact Sheets relating to septic systems & domestic wastewater treatment systems include
  • Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
  • Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
  • Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
  • Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
  • Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)

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