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SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SEPTIC CARE INSTRUCTIONS
SEPTIC D-BOX INSPECTION
SEPTIC DRAINFIELD FAILURE DIAGNOSIS
SEPTIC DYE TEST PROCEDURE
SEPTIC FAILURE SIGNS
SEPTIC INSPECTION & TEST GUIDE
SEPTIC LIFE EXPECTANCY
SEPTIC SUPPLIES & PARTS
SEPTIC SYSTEM DESIGN ALTERNATIVES
SEPTIC SYSTEM DESIGN BASICS
SEPTIC SYSTEMS, HOME BUYERS GUIDE to
SEPTIC SYSTEM SAFETY WARNINGS
SEPTIC TREATMENTS & CHEMICALS
SEWAGE & SEPTIC CONTAMINANTS
SEWAGE BACKUP, WHAT TO DO
SEWAGE BACKUP TEST & CLEANUP
SEWAGE BACKUP PREVENTION
SEWAGE CONTAMINATION in buildings
SEWAGE CONTAMINANTS in FRUIT / VEGETABLES
SEWAGE EJECTOR / GRINDER PUMPS
SEWAGE LEVELS in SEPTIC TANKS
SEWAGE NITROGEN CONTAMINANTS
SEWAGE PATHOGENS in SEPTIC SLUDGE
SEWER BACKUP PREVENTION
SEWER GAS ODORS
SEWER LINE REPLACEMENT
SINKHOLES, WARNING SIGNS
SMELL PATCH TEST to Track Down Odors
SOAKAWAY BED FAILURE DIAGNOSIS
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
TOILETS, DON'T FLUSH LIST
TRAPS on PLUMBING FIXTURES
TREATMENTS & CHEMICALS, SEPTIC
VIDEO GUIDES: Septic Videos
WASHING MACHINES & SEPTIC SYSTEMS
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WASTEWATER TREATMENT BASICS
WATER, WELLS, WATER TANKS: TESTING GUIDE
WINTERIZE A BUILDING
On this page we describe the depth at which septic tanks are installed and we explain the use of septic tank risers to make it easier to pump out, clean, or service deeply-buried septic tanks.
Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical review by industry experts has been performed and is ongoing - reviewers are listed at "References." Comments and suggestions for content are welcome.
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This septic tank depth article is part of our septic system article series that summarizes guidelines on the required septic tank size based on anticipated level of daily gallons of sewage wastewater flow. The typical residential septic tank size required for a given average daily sewage wastewater flow in gallons is provided in a table of septic tank sizes. Also see DRAIN LINE DEPTH where we describe the depth of sewer and septic system piping.
This chapter also explains how to calculate septic tank volume based on septic tank inside dimensions measured in feet, and we discuss the sizing, installation, and functions of septic tank tees to prevent septic system clogging. Links to related septic system testing and design information are given.
Septic tanks can be installed pretty much at any depth in the soil. Even in freezing climates, the septic tank serving an occupied home or even an unoccupied one is unlikely to freeze, partly because of latent heat the bottom of the septic tank receives from the earth and partly because of the heat generated by the bacterial action going on in the septic tank. (DO NOT add antifreeze to a septic system.)
Factors Determining Septic Tank Depth
The principal factors that determine the actual depth at which a septic tank is likely to be buried (and thus how deep you may have to dig to find the septic tank) at a particular site include:
What if the septic tank is buried deep below ground surface?
Indeed we've seen septic tanks partially above ground, and others buried more than six feet deep. It's not necessarily a mistake, and deep septic components may be required by site conditions, but here are some considerations when the septic tank is more than a foot below ground surface:
Safety warning: Be sure that the septic tank riser and all septic tank covers are sound and secure since falling into a septic tank can be fatal. See SEPTIC & CESSPOOL SAFETY .
Frequently Asked Questions (FAQs)
Questions & answers or comments about how deep the septic tank should be placed and how deep in the ground it may be found at various building sites.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Design Manuals for Septic Systems