Protecting Public Health and the Environment.

Septic Tank Pumping and Septage Disposal

Septic systems require periodic maintenance that includes pumping out the accumulated scum, sludge, and wastewater (cumulatively called septage) from the septic tank. Septage can present public health hazards and generates strong odors. To prevent public health hazards and nuisance conditions, septage must be collected (pumped), transported, stored, and disposed of according to the following rules:

Septage may contain any number of pathogens that pass in feces or bodily fluids. The pathogens may include, but are not limited to, bacterial organisms (e.g., Salmonella, Shigella, and Clostridium), parasites (e.g., pinworm, roundworm, and hookworm), and organisms that cause amoebic dysentery, polio, and hepatitis. Properly managing septage after its removal from the septic tank through disposal or beneficial reuse is critical in ensuring that public health is protected from the pathogens present in septage. Septic tank pumpers not only help property owners maintain their septic systems by pumping septic tanks but also protect property owners and the public from the various health hazards associated with septage.


Septage is a general term for the contents removed from septic tanks, portable toilets, privy vaults, wastewater holding tanks, type III marine sanitation devices, recreational vehicle holding tanks, very small wastewater treatment plants, or semipublic facilities (e.g., schools, motels, mobile home parks, campgrounds, and small commercial endeavors) receiving wastewater strictly from domestic sources. Nondomestic (commercial and industrial) wastes and drinking water treatment residuals held in a holding tank are not included in this definition. Septage is considered domestic when it comes from residences or facilities with waste characteristics similar to residential sources like schools, motels, campgrounds, and office buildings. Septage is considered nondomestic when it comes from commercial or industrial processes including, but not limited to, grease traps, sand traps, or car wash sumps. If domestic and nondomestic septage is comingled the entire volume of septage is considered nondomestic.

Classification of septage as domestic or nondomestic has an impact on the allowable disposal or beneficial reuse of the septage. Septage generators and pumpers must be aware of the septage classifications of the materials they are generating, pumping, or transporting so proper disposal can be achieved. Additionally, it is recommended that facilities producing domestic and nondomestic wastewater isolate the wastewater plumbing and discharge these wastewater sources to separate septic tanks. This allows the domestic and nondomestic septage to be segregated so that the disposal and beneficial reuse options are maximized.

Septic Tank Pumping

Septic tanks will function satisfactorily until the sludge fills over 40% of the volume of the tank (as measured from the bottom of the septic tank to the invert of the tank outlet), or the scum reaches the top of the inlet or outlet baffle in the tank. For a septic tank to function properly (scum to be trapped within the inlet and outlet baffle area, and sludge settling and retention), the inlet and outlet baffles within the tank must be intact and in good condition. Proper baffle design is described in IDAPA and Anytime a septic tank is pumped or a drainfield is repaired, the inlet and outlet side of the septic tank should be uncovered, and the baffles should be inspected to ensure the septic tank is in good working order.

Before the tank reaches a sludge volume of 40% of the volume of the tank, it should be pumped by a permitted pumper. If the tank is not pumped, it will be unable to perform its wastewater separation function, which will allow the solids and greases to be carried out into the drainfield. If solids and greases reach the drainfield, they will fill and clog the soil pores causing the drainfield to fail resulting in sewage backing up into the home or business, the sewage in the tank to overflow, or effluent to reach the ground surface around the drainfield. Under regular use (two people in the first bedroom and one person in every other bedroom), it is recommended that the septic tank be inspected every 3–5 years and pumped as needed.

Other system components such as dosing chambers or mechanical treatment plants should also be checked on an annual basis for pumping needs. Both dosing chambers and mechanical treatment plants will not be capable of operating properly if sludge levels get too high within these tanks. It is recommended that a property owner consult their system operation and maintenance manual or manufacturer information to determine when these system components should be pumped by a permitted pumper.

Handling, Transportation, and Disposal of Domestic Septage

DEQ has established minimum standards, Rules Governing the Cleaning of Septic Tanks (IDAPA 58.01.15), for pumping or cleaning septic tanks and/or transporting or disposing of human excrement. The operation of any pumping/tank truck or any other device or equipment used or intended to be used for the purpose of pumping, transporting, or disposing of domestic septage within or through Idaho must obtain a permit for such activity from one of Idaho’s seven public health districts.

The public health districts permit and inspect septage pumping and transportation equipment under a memorandum of understanding between DEQ and the public health districts. The public health districts also approve one-time disposal locations and methods for domestic septage. DEQ reviews all Septage Management Plans for Land Application (SMPLA) of domestic septage for beneficial use of domestic septage through continual land application. Land application is considered continual when domestic septage is land applied by one or more pumpers to the same site two or more times per year.

Domestic Septage Disposal

Domestic septage may only be disposed of in conformance with the methods allowed by the Rules Governing the Cleaning of Septic Tanks (IDAPA 58.01.15). Those methods include the following:

  1. Discharging to a public sewer
  2. Discharging to a sewage treatment plant
  3. Burying under earth in a location and by a method approved by DEQ
  4. Drying in a location and by a method approved by DEQ

The first two methods of disposal require approval from the owner, responsible charge operator, or superintendent of a wastewater treatment plant or the owner/responsible charge operator of the public sewer. The pumper must be aware that discharging to a public sewer without the proper approvals puts the pumper in violation of the National Pollutant Discharge Elimination System pretreatment requirements and associated federal codes.

Disposal methods 3 and 4 are associated with disposal or land application of domestic septage. Nondomestic septage may not be approved for one-time disposal or beneficial reuse. Approval for one-time disposal of domestic septage must be obtained through the health district where the one-time disposal site is located. Pumpers seeking approval of continuous domestic septage land application sites need to contact the DEQ regional offices and follow DEQ’s guidance for land application of domestic septage.

One-Time Domestic Septage Disposal

One-time domestic septage disposal may be allowed through burial or drying. Approval for one-time domestic septage disposal must be obtained through the public health district where the one-time disposal site is located. Individuals seeking approval for one-time disposal must submit information to the public health district and allow the district to access the proposed site to ensure the site is suitable for one-time domestic septage disposal. Application for one-time disposal and evaluation fees may be required by the public health district for this activity.

One-time disposal accomplished through burial (incorporation into soils) shall ensure the following:

  • Complete burial is accomplished within 6 hours of domestic septage disposal, and
  • The disposal depth meets the separation distance requirements of IDAPA for ground water and IDAPA for surface water in soil design group C soils.

One-time disposal accomplished through drying (no incorporation into soils) shall ensure the following:

  • The domestic septage is adjusted to a pH of at least 12 for a full 30 minutes before the septage is applied to the land application area, and
  • The disposal depth meets the separation distance requirements of IDAPA for ground water and IDAPA for surface water in soil design group C soils.

Additionally, sites used for one-time domestic septage disposal must meet specific site restriction timelines. Site restrictions are in place to ensure that pathogens and vectors are reduced to protect public health and the environment. Site restrictions include crop harvesting and site access restrictions. Site restrictions must be met for one-time domestic septage disposal locations for both pH and non-pH adjusted domestic septage as outlined in Tables 3, 4, 5, and 6 in the Guidance for the Land Application of Domestic Septage.

Beneficial Reuse of Domestic Septage (Continual Disposal)

DEQ recognizes the value in reuse of domestic septage through land application at nonpublic contact sites for soil augmentation purposes. Continual land application of domestic septage is regulated under 40 CFR 503 and the Rules Governing the Cleaning of Septic Tanks (IDAPA 58.01.15). Due to the nature of domestic septage land application as a drying method, DEQ approval of septage land application facilities is required before operational startup. To obtain DEQ approval for continual domestic septage land application, a Septage Management Plan for Land Application must be submitted to DEQ and approved by the agency. To assist in developing an acceptable Septage Management Plan for Land Application, DEQ developed the Guidance for the Land Application of Domestic Septage. This guidance will help interested parties develop a management plan that meets their domestic septage disposal needs while providing nutrient augmentation to the soil for crop growth purposes. Continual land application is limited to domestic septage only.

Other Pumpable Wastes

Several other types of pumpable wastes exist in addition to domestic septage. Nondomestic septage and other pumpable wastes must be disposed of properly. To determine the acceptable disposal locations some forms of pumpable waste must be characterized to determine if it is a hazardous waste before transportation and disposal. For non-hazardous pumpable wastes, proper disposal may occur at sewage treatment plants, solid waste landfills, or other approved disposal locations. Some non-hazardous pumpable wastes may also be land applied under an approved sludge management plan (IDAPA Pumpable waste that meets the definition of a hazardous waste may only be disposed of at a permitted hazardous waste treatment, storage, and disposal facility. Pumpable waste generators, transporters, and disposers are encouraged to contact their regional DEQ office to determine acceptable disposal options for the pumpable waste.