Types of septic systems
A septic tank plus a drain field of gravel or stone trenches.
Conventional (gravel trench) system
It is the standard system for a single-family home when the soil is suitable.
Gravel systems take up a lot of room and may not fit every lot.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Chamber system
Uses a series of connected chambers instead of gravel in the trenches. The EPA says gravelless designs have become a conventional technology.
Chambers are easier to deliver and build, and suit high groundwater, homes with uneven use (like vacation homes), and areas where gravel is scarce.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Drip distribution system
Treated water is pushed through small drip lines buried in the top 6 to 12 inches of soil, so no large mound is needed.
It needs a large dose tank, electricity and more maintenance. In Oklahoma a drip field must follow an aerobic treatment unit and be designed from a soil profile description.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Mound system
A drain field built inside a mound of sand above the natural ground. A pump sends effluent to the mound in doses.
Used where soil is shallow, groundwater is high or bedrock is near the surface. Mounds need a lot of space and periodic maintenance. Missouri describes a sand mound as having at least 12 inches of clean sand above the original soil.
Sources: US EPA, Types of Septic Systems (last updated May 4, 2026); Missouri DHSS, Onsite Wastewater Treatment Systems (types page, no date shown)
Aerobic treatment unit (ATU)
Pumps air into the tank so bacteria break down waste more completely, then usually disinfects and sprays or drips the water. Used on small lots, poor soils and high water tables. Expect lifetime maintenance. See the aerobic septic systems guide.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Sand filter system
Septic tank effluent is pumped over a lined box or bed of sand, which filters and treats it before it goes to the drain field.
The EPA says sand filters give a high level of nutrient treatment and suit high water tables or sites near water, but cost more than a conventional system.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Lagoon (wastewater stabilization pond)
A sealed earthen pond that treats wastewater with natural biological processes. Sewage passes through a septic tank first.
Missouri's rule says a lagoon can work in rural areas where soils are not suited to absorption fields. Oklahoma's rule requires lagoons to be total retention (no discharge) and at least 7 feet deep.
Lagoons need more land than other systems. The Missouri health department says lagoons typically need more land because of greater setback requirements.
Sources: Missouri DHSS, Onsite Wastewater Treatment Systems (types page, no date shown); Missouri 19 CSR 20-3.060 Minimum Construction Standards for On-Site Sewage Disposal Systems (Code of State Regulations, 9/30/20); Oklahoma DEQ, OAC 252:641 Individual and Small Public On-site Sewage Treatment Systems (amendments effective 9-15-24); Missouri DHSS, Onsite Wastewater Frequently Asked Questions (no date shown)
Where lagoons are allowed in Missouri and Oklahoma
Missouri (19 CSR 20-3.060(6)(D)): single-home lagoons are not generally suitable in subdivisions with lots under 3 acres, and only one home may use a lagoon. Ponds may be used where soils are very slowly permeable, such as perc rates slower than 120 minutes per inch, and there are no significant groundwater limits.
Missouri setbacks: at least 75 feet from property lines, 200 feet from the nearest existing home, 100 feet from the home it serves, 100 feet from a drinking water supply, and 50 feet from a stream or lake. The rule allows these to be modified for site conditions or local codes.
Oklahoma (OAC 252:641-15 and Appendix A): a lagoon requires a lot of at least 2 1/2 acres, is not allowed in net evaporation Zone 1, and is not acceptable in Zones 7 through 10 when flow is under 100 gallons per day. It must not be shaded or blocked from wind by trees or terrain, and must be fenced.
| Rule | Missouri | Oklahoma |
|---|---|---|
| Lot size | Not generally suitable in subdivisions with lots under 3 acres | Lot of at least 2 1/2 acres (Appendix A, Figure 1) |
| Soil | Very slowly permeable soils, such as perc slower than 120 min/in | Allowed at any perc rate (Appendix A, Figure 2) |
| Where not allowed | Where groundwater limits exist | Net evaporation Zone 1; Zones 7 to 10 when flow is under 100 gallons per day |
| Homes per lagoon | One single-family home | Not stated in the sections read |
| Other | Setbacks of 75 ft (property line), 200 ft (other homes), 100 ft (own home, water supply), 50 ft (streams) | Total retention, at least 7 ft deep, septic tank first, fenced, no shade or wind block |
| Rule | 19 CSR 20-3.060(6)(D) | OAC 252:641-15; Appendix A |
Sources: Missouri 19 CSR 20-3.060 Minimum Construction Standards for On-Site Sewage Disposal Systems (Code of State Regulations, 9/30/20); Oklahoma DEQ, OAC 252:641 Individual and Small Public On-site Sewage Treatment Systems (amendments effective 9-15-24)
Cluster or community system
One shared treatment and dispersal system serves two or more homes or buildings under common ownership. Often found in rural subdivisions.
Source: US EPA, Types of Septic Systems (last updated May 4, 2026)
Typical installed cost by system type [EST]
[EST] National installed cost ranges from HomeAdvisor (updated Jun 20, 2026). This Old House (modified 03/12/2026) shows the same ranges, sourced from Angi.
| System | Installed cost [EST] |
|---|---|
| Conventional (anaerobic) | $3,000 to $8,000 |
| Chamber | $5,000 to $12,000 |
| Sand filter | $7,000 to $18,000 |
| Drip | $8,000 to $18,000 |
| Aerobic | $10,000 to $20,000 |
| Mound | $10,000 to $20,000 |
Source: HomeAdvisor, Septic System Installation Cost (updated Jun 20, 2026)
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Find a licensed septic proCommon questions
What is a conventional septic system?
A septic tank plus a gravel or chamber drain field in the soil. The EPA says it is typically installed at a single-family home or small business.
What type of septic system do I need if my soil is poor?
The EPA lists mound systems for shallow soil, high groundwater or shallow bedrock, aerobic units for small lots and poor soils, and sand filters for high water tables. Your site evaluation decides which your state allows.
Are septic lagoons allowed in Missouri and Oklahoma?
Yes, with limits. Missouri says single-home lagoons are not generally suitable on subdivision lots under 3 acres and allows one home per lagoon. Oklahoma requires at least 2 1/2 acres and bars lagoons in net evaporation Zone 1.
Which septic system is cheapest?
[EST] HomeAdvisor (Jun 20, 2026) lists a conventional anaerobic system at $3,000 to $8,000, the lowest range, with mound and aerobic systems at $10,000 to $20,000.