Repairing Septic Tank Field Line

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    • #279272

      We have a wet spot of grass in a small area over the septic tank field lines and have been told by a professional it is necessary to replace the entire field system. My boyfriend is extremely talanted around the house and is wanting to know if there is a way (and how!?) to replace only the part of the field that is leaking instead of digging up the entire yard?!

      Thanks for any help or direction you can provide!!

      Audrey – Dallas, Ga.

    • #300421
      John Aldrich1

      Audrey, it is difficult to determine exactly what is occurring in regard to your leach field failure without the benefit of a site visit to inspect the system. However, I suspect that the clogging mat, which grows at the soil/gravel interface, has attained a thickness to the point where the percolation rate of the effluent through it has become less than the application rate of the effluent flowing from your septic tank. This inevitable condition occurs in every soil absorption system. If the effluent cannot percolate through the clogging mat rapidly enough, then it flows in the path of least resistance. In the case of your leach field, that path is to the surface of the ground above the leach field at the wet spot. The clogging mat however grows at the infiltrative surface over the entire area of the bottom of the leach field, so it would be a futile effort to attempt a repair by excavating the leach field at the wet spot.

      At times, it is possible for the existing leach field to recover its permeability through prolonged resting. This process would require the installation of an alternate leach field, which would receive the effluent while the existing field rests. The required area of this alternate leach field would be half the area of the existing leach field. Chances are that the condition of the existing leach field cannot be determined. If this is the case with your leach field, then I recommend that the existing field be abandoned.

      If you decide to replace the leach field, consider installing 2-half sized leach fields equipped with a 4-inch, NDS brand diversion valve. Cover the valve riser with a 10-inch round irrigation valve box to allow for easy access. The top of the box is set at the final grade elevation. The valve will allow the alternation of flow to the fields. Use half the field for 1-year while the other half rests. Turn the valve annually on the 4th of July, SEWAGE INDEPENDENCE DAY. Celebrate your independence of the sewer grid, and remember that with this independence comes the responsibility of a sewage treatment system operator.

      I recommend the use of plastic leach field chambers such as the standard Advanced Drainage Systems, Inc. Bio-Diffuser®. ( Cover each chamber leach field with a 4-foot wide sheet of geotextile fabric (landscaping fabric). The geotextile will prevent the migration of silt into the void under the chambers. The fabric also acts as a wick, wicking by capillary attraction the effluent up over the chamber units, and then into the soil.

      Install 4-inch monitoring and ventilation ports to the ground surface on each end of each field. If you decide to try to salvage the existing field, then after the field becomes unsaturated, excavate the soil at 2 locations above the distribution pipes, and install 4-inch tees in the 4-inch perforated pipes. Install risers to the ground surface so that atmospheric air has a direct path to the gravel in the leach field. This step is very important. Atmospheric air contains approximately 21 percent oxygen, while the oxygen content of the air between the soil particles 2 feet below the ground is less than 5 percent. Aerobic microbes (and macrobes such as worms, grubs and insects) accomplish the consumption of the clogging mat. Also, chemical oxidation of the ferric sulfide, an iron compound, which is a major constituent of the clogging mat, occurs when the environment of the leach field becomes aerobic.

      The 4-PVC risers are covered with plastic 6-inch round irrigation valve boxes. The tops of the irrigation valve boxes are set at the final grade elevation. The boxes will allow easy location, easy access, and you can run the lawn mower right over them. Typically the covers of the boxes are green.

      The tops of the in-use field monitoring ports are fitted with 4-inch female threaded adapters, and threaded plugs to prevent sewer gas odors from emanating into the yard. The tops of the resting field ventilation ports are fitted with a 4-inch female adapters, and plastic drain grates. The drain grates just prevent small critters, such as mice and ground squirrels from entering the leach field, while allowing ventilation to occur.

      The ventilation ports will allow atmospheric oxygen to enter the leach field, and this will create an aerobic condition in the resting leach field. The oxygen will oxidize the Ferric sulfide (that black slimy crap), a major component of the clogging mat. Also, the aerobic condition will allow the aerobic microbes, present in the surrounding soil, to migrate to the clogging mat and consume the organic matter constituent of the clogging mat, and consume the dead bodies of all their anaerobic microbial cousins. Exchange the solid threaded plugs with the drain grates when the valve is turned on SEWAGE INDEPENDENCE DAY.

      While you are involved with the major renovation of your septic system, I recommend that 20-inch plastic risers be installed over the inlet manhole, and the outlet manhole of the septic tank. The covers of the risers should be at the final grade elevation to allow easy access to the tank. Let’s face it, if you must excavate the soil over the septic tank manhole with a shovel, chances are that this chore will be avoided. I use Tuf-Tite brand risers.

      I also recommend that the outlet tee of the tank be fitted with a septic tank effluent filter. The brand that I use is manufactured by the Tuf-Tite company,( although there are several other high quality filters on the market. The filter will reduce the organic matter, and floating suspended solids, in the effluent from flowing into the leach field. Clean the filter annually on SEWAGE INDEPENDENCE DAY.

      Another chore that should be performed annually is the measurement of the sludge accumulation in the primary chamber of the septic tank. The sludge can be measured with a “SLUDGE JUDGE.” Do an Internet search to obtain this neat device. ( I recommend the implementation of the “1/3 RULE” of sludge removal. When the level of the sludge is 1/3 the total liquid depth of the septic tank, it is time to remove it.

      The final chore to be performed on SEWAGE INDEPENDENCE DAY is to record all of the maintenance performed on the system in a maintenance log. I prepare a SEWERS CAN BE BEAUTIFUL operation manual for each of the septic systems that I install for my clients. The manual contains a description of the system design, photos of the system components, an as-built plan, a description of the required maintenance procedures, a copy of the permit, and the maintenance log. The manual becomes an excellent sales tool when the time comes to sell the home. The manual answers all questions a potential buyer may have regarding the performance of the septic system, and will allay the fears typically encountered when purchasing a home served by a septic system.

      Well Audrey, I had better end this lengthy diatribe. If all soil absorption type septic systems were designed and constructed to the above standards, then there would be far fewer failed septic systems. Maintenance is the key to successful septic systems. However, if the required maintenance is difficult, or impossible, then chances are it will not be performed. If you would like photos of my typical standard system, send your request to me via e-mail. My address is

      John Aldrich (Septic Tank Yank)
      Septic System Consultant
      Timnath, Colorado

      » This message has been edited by John Aldrich on 25 July 2003

    • #300422


      Your reply to Audrey’s problem was outstanding. I learned a lot from it. I’m also thankful that in the SF Bay Area we don’t have many septic systems (there are some in the remoter regions of Napa, Marin, Sonoma, and Solano counties). I’m glad we can call on guys like you to deal with those systems, because I sure as heck wouldn’t know what to do to fix ’em…


    • #300423
      John Aldrich1

      NickthePlumber, thanks for the compliment. You say that you are thankful that there are not many septic systems in the SF Bay area. Well, I can only say that my clients are thankful to be served by state-of-the-art individual on-site sewage treatment systems whose front end installation costs are probably significantly less than the typical tap fee on a central sewage collection system. These properly designed and properly operated systems are by far superior in treating domestic sewage than are the centralized systems. Additionally, there are no monthly service fees and no service fee increases, unless the system owners choose to pay an independent service provider to operate and maintain their systems.

      Historically, septic systems have earned a poor reputation for long term performance and functionality. This is because the regulations defining the prescriptive design features of septic systems, which have been promulgated by regulatory agencies, allow systems that resist easy maintenance, and in fact, prescribe systems that are designed to fail.

      Well Nick, you may be thankful for the centralized sewage collection and treatment systems that have been constructed in this country over the past century or more, but these massive, expensive infrastructures are not without problems, and thousands of miles of sewerage, and thousands of treatment plants, are in need of replacement. Whenever a large sewer pipeline fails or breaks, millions of gallons of untreated sewage are discharged to the environment, causing immense environmental damage, and an extensive threat to public health.

      This quote is from the World Bank publication, “Sanitation and Disease.”

      “Those whose job it is to select and design appropriate systems for the collection and treatment of sewage … must bear in mind that European and North American practices do not represent the zenith of scientific achievement, nor are they the product of a logical and rational process. Rather, [they] are the product of history, a history that started about 100 years ago when little was known about the fundamental physics and chemistry of the subject and when practically no applicable microbiology had been discovered…. These practices are not especially clever, nor logical, nor completely effective-and it is not necessarily what would be done today if these same countries had the chance to start again.”

      Audrey has sent an e-mail message to me, thanking me for my response, and asking some additional questions. It appears that the septic system professional that has inspected her failed system has bid $1,900 to “fix” the system. I am not sure of how he plans to fix the system, but I suspect that he will remove the old leach field and then just duplicate the original poor design. This new leach field is destined to fail again in the future. Hopefully, Audrey will take my advice, and effect a proper repair to her system.

      Audrey wrote:

      If you don’t mind I would like to ask a couple more questions. I’m not sure exactly how this “consulting” thing works once we’re off the bulletin board, so if you do mind, I understand, so just let me know if answering more questions is more than you are willing to do unless I want to hire you.

      My response:

      Audrey, you will be receiving an invoice in the amount of $5,000 in the US mail for my consulting services!!!!! Naa, just kidding! ;>) There is no consulting fee.
      The value of the Discussion Forum is that you can obtain valuable advice at no cost. My hope is that you heed my advice. The value to me is that good advice can be distributed throughout the world, which will only improve septic system practices as the technology evolves. This can only be good for the industry, and it is my way of giving back something to the industry that has supported me in my career. I have done quite well. My only hope is that those who seek advice will follow through and implement the design features of septic tank/soil absorption systems that I have developed over the past 27 years in the business.

      Now to answer your questions…….

    • #300424


      Thanks for your comments. You raise some intriguing questions. The main one is which is better…an individual septic system or a municipal sewer treatment complex? I’ve often wondered about this, not only as regards waste water treatment, but also such things as private well water vs. municipal water, bottled LPG vs muncipal piped NG, and even private solar power vs. electricity from “the grid.”

      I certainly like the idea of self-sufficiency, and I support anything that will allow homeowners to provide their own water, power, and waste disposal.

      I heavily urbanized areas like the SF Bay Area and NYC, private water wells are out of the question unless you want to go to inordinate expense. I actually thought about installing a well on my property and had an engineer do an analysis. The well would have to be drilled about 100 feet and even then it would not be guaranteed to provide pure water. (It would definitely provide water, however, that could be used to to water my garden and fruit trees). My lot is is in a populous city, about 4000 sq ft (half of which is covered by my home’s footprint) and is not sufficient for a septic system. That leaves the solar power option, which I plan to install. The cost for a good system is about $20,000, of which about 50% could be recovered by tax credits. I plan to do it.

      For those who live where septic systems are viable. that option seems to offer many benefits. If these systems were installed according to the best current scientific principles that you describe, there would be fewer problems with such systems.


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