Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SEPTIC CARE INSTRUCTIONS
SEPTIC D-BOX INSTALL REPAIR
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 GAS ODORS
SEWER LINE REPLACEMENT
SINKHOLES, WARNING SIGNS
SMELL PATCH TEST to FIND ODOR SOURCE
SOAKAWAY BED FAILURE DIAGNOSIS
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
ALTERNATIVE & WATERLESS TOILETS
TOILETS, DON'T FLUSH LIST
TRAPS on PLUMBING FIXTURES
TREATMENTS & CHEMICALS, SEPTIC
VIDEO GUIDES: Septic Videos
WATER CONSERVATION MEASURES
WATER SOFTENERS & CONDITIONERS
WATER SUPPLY & DRAIN PIPING
WATER, WELLS, WATER TANKS: TESTING GUIDE
WASHING MACHINES & SEPTIC SYSTEMS
WASTEWATER TREATMENT BASICS
WINTERIZE A BUILDING
Septic tank flooding or back flooding:
What causes flooded septic tanks or abnormally-high sewage levels in septic tanks and what do we do about it? A flooded septic tank can cause a sewage backup in a building or ejector pump flooding. Backflooding means that water or wastewater is flowing backwards into the septic tank from a soakbed or drainfield or from surface runoff.
To understand how to fix the problem of high waste levels in a septic tank we need to diagnose the cause, then outline, in order from least costly to more expensive, the approaches to fixing this problem.
Here we explain back-flooded septic tanks & an understanding of how to diagnose abnormal septic tank sewage levels can tell us what septic system repairs are needed. Do we just need to seal a pipe connection, clear a clogged sewer line, or do we need to control surface runoff, fix septic tank leaks, or replace a failed septic soak-bed?
Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.
Septic Tank Flooding & Back-Flooding: Why it is important to diagnose & fix water leaking into the septic tank
Reader question: my leach field floods in the yard and flows backwards into my septic tank
4/17/14 in the FAQs section of SEPTIC DRAINFIELD FAILURE DIAGNOSIS Joe Paciga said:
Hello, thanks for all the great information your site provides. I live in Southeaster VA, 60 feet above sea level. My house is 17 years old and I bought it 2 years ago. I have septic problems. I will try to make this short, but I will give you all the info too.
My leach field is flooding the surface of my yard. I have planned to replace the field, but I decided to talk to a professional about my problem before making a wrong decision.
Basically he said there is a "why" to the reason my field is failing. He asked do I have any leaking toilets or anything else, answer is no. I thought it may have been crushed by a heavy truck I had in the yard.
My own fault. I inspected the D box, all seems fine there. He said it sounds like you might be pumping extra water into field for some reason, and that's why I'm having problems. We have had the wettest winter in over 20 years. I have concrete 2 tank system. The 2nd tank to pump the effluent to back yard. Recently I had them pumped out the monitored the pump tank.
After a recent rainstorm of about 2 inches of rain, I checked the tank. The effluent level rose 2 feet overnight. So, there has to be a leak. Thus the extra pumping into my leach field and failure.
Ok, so is there a leak, but how and where. With the tanks relatively young, (I pour concrete for a living) I doubt they are broken. What about the gasket for tank tops or the pipe in between the 2 tanks. What would be the most likely ground water intrusion to the system?
No tree roots remotely close.
Reply: tips for diagnosing septic tank back-flooding problems
I've dealt with this leach field flood problem as have countless others for a long time now and appreciate the frustrations involved. The professional you cite names some reasons that the field could be flooded, but may be shooting in the dark in that unless we do some diagnosis we don't know what's actually going on and don't know what to fix.
I agree that a running toilet or water softener stuck in regeneration cycle can flood a drainfield.
So can water leaking into the tank at the tank top, at the tank inlet, tank outlet, or from a crack or damaged tank bottom, sides, or cover or from an improperly sealed septic tank access riser.
Water can also back-flood a septic tank (I'm more or less "inventing" this term but it will be obvious to most) by running backwards from a flooded septic drainfield into the septic tank.
The drainfield may be flooded by high ground water (which means the drainfield is not properly constructed and is too low), or by mishandling of surface or subsurface seasonal runoff that needs to be intercepted and directed away from the drainfield using a curtain drain or surface swale or both.
How to Diagnose a Flooded Septic Tank - a common cause of building sewage backups
While I agree that we would expect a relatively new septic tank to be un-damaged, it makes sense to actually inspect the tank so that we don't waste time with a lot of arm-waving speculation when a little bit of digging and looking can go a long way towards sorting out the problem.
Definition of Flooded Septic Tank: a septic tank in which the wastewater level is above the bottom of the septic tank outlet pipe's bottom-most surface is flooded, not working properly, and inviting a sewage backup into the building.
In simple terms the septic tank wastewater level may be abnormally high because
Definition of Septic Tank Back-Flooding: a septic tank that is suffering back-flooding is one into which wastewater can be observed entering the septic tank at its outlet end or outlet effluent pipe as the septic tank is being pumped or emptied.
A partially-full septic tank may still be considered flooded if it is filling too quickly
Watch out: a septic tank may also be technically flooded even if the total level of wastewater is below the septic tank outlet. How the heck could that be? We encountered just this condition at a home recently. The septic pumping company reported having completely emptied the septic tank during a period of wet soils and lots of surface runoff due to snow-melt.
A day later the building basement suffered a flood that owners correctly believed was due to surface runoff and snow melt leaking into the building. But in the course of diagnosing that condition the septic contractor returned to the home to inspect the septic tank liquid level again.
In a day after a (reportedly) 1,500 gallon septic tank had been pumped "empty" according to the contractor the tank was by his estimate 85% "full" again. The home, occupied by a single older resident, certainly had not produced 3/4 of a septic tank's worth of wastewater in a day.
As the owners believe there was no wastewater being produced by running toilets nor other water-dispensing equipment, it was evident that surface runoff and snow-melt that were flooding the home's basement were probably also the source of water entering the septic tank. Further diagnosis was needed to determine if the septic tank flooding was due to leaks into the tank or due to a failed drainfield that was also saturated by snow-melt
Relationship of Septic Tank Baffles to Septic Tank Flooding
Watch out: A broken or missing septic tank baffle on the tank inlet side invites sewer line clogs between building and tank and building sewage backups; a broken or missing septic tank baffle on the outlet end of the septic tank means we're pushing solids into the drainfield or soakaway bed, basically destroying that expensive component by clogging the soil around the drainfield trenches with solid waste, grease, scum, etc.
Details about septic tank baffle inspection and repair are at
There we explain that by inspecting the septic tank sewage level prior to pumping the septic contractor can see if the waste level is abnormally high (over the baffles - a flooded septic tank) or abnormally low (a leaky septic tank if the tank has been in use long enough that it should be full).
Open & Inspect Septic Tank Inlet & Outlet to Diagnose Tank Flooding
By opening the tank at its inlet and outlet ends, exposing the septic tank baffles and pipe connections, and inspecting with some thought, particularly if we make observations while having the septic tank pumped, we can see where water is coming in and thus know what needs to be done next.
Watch out: at FLOODED SEPTIC SYSTEMS, REPAIR [live link is given at Continue Reading just below] we explain how to fix a problem with septic tank or soakbed or drainfield flooding. But be warned, that while in an emergency we might pump the septic tank, simply pumping the septic tank won't fix this problem and worse, if the back-flow rate into the septic tank is rapid (as it often is) you are simply wasting your money as back-flooding from a drainfield or surface runoff will quickly fill the septic tank again in hours to days. Also
See SEPTIC BACKUP PREVENTION for tips to avoid a septic problem during times of anticipated heavy septic system usage.
Continue reading at FLOODED SEPTIC SYSTEMS, REPAIR to read suggestions for repairing a flooding septic tank or soakbed system, or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
(July 7, 2014) Anonymous said:
Anon, the next point to check is the distribution box. Look for flooding there. Look at the flow of effluent into all the drainfield lines. Indeed the field may be shot but lets make sure.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References
Design Manuals for Septic Systems
Onsite Wastewater Disposal Books