Drain Field Wet Spot

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    • #279002
      Avatar photoAntony

        I have a large house(with a attached mother-in-law suite), two septic tanks in series, and a fairly good grade on my drain field. The system is six years old and just this year I have developed a wet spot at the edge of my drain field. It’s definetly sewer water in the spot. Is this a problem or something I should ignore? Anyone with info pls let me know something.

      • #299773
        Avatar photoarmdiver

          If it is at the end of the field, your drain bed is probably clogged or has seen its’ day. If you have room, you could lengthen it. It probably won’t resolve itself. A product called “Amerisep Super” claims to unclog grease over a period of 90 days or less, but didn’t work for me. I ended up elongating my field by 70 feet and is percolating fine.

        • #299774
          Avatar photoJohn Aldrich1

            jeff_stockton, the appearance of septic tank effluent on the surface of the leach field is an indication that the clogging mat which is formed on the soil below the leach field has reduced the percolation rate of the effluent into the soil to a rate that is slower than the application rate. The effluent will flow in the path of least resistance, in this case, that path is to the surface at the edge of your leach field.

            Do not ignore this potential threat to the environment, and threat to the public health (particularly your family’s health). In my view, the correct method of repair of the soil absorption system is to install a diversion valve in the septic tank effluent pipeline, and install another leach field. Alternating the effluent flow from one leach field to the other on an annual basis will give you the ability to control the thickness of the clogging mat, and therefor, the ability to control the percolation rate of the effluent into the soil below the leach field.

            Monitoring and ventilation ports should be installed in each leach field so that the field which is in the “resting” mode can be ventilated with atmospheric air. The leach field riser port that is on the “in-use” field is fitted with a solid, threaded plug to prevent sewer gasses from emanating into the yard.

            Expanding the size of the leach field will not be a long term solution to the problem. If alternating leach fields were installed from the “get-go”, and if you performed your annual septic system maintenance duties, you would not have this problem. JWA

          • #299775
            Avatar photojeff_stockton

              Great! Now someone mentions periodic maint. Pls tell me what I should have been doing all along.

            • #299776
              Avatar photoJohn Aldrich1

                Jeff, unfortunately, you are one of the many thousands of victims of the on-site sewage treatment system establishment in this country. The history of how this industry has so SLOWLY progressed is almost unbelievable. It is not your fault that the septic system serving your home is failing. It is the fault of the Regulator that approved the inadequate system, the fault of the engineer that designed the system, and the fault of the contractor that installed the system.


                Regulatory Agencies all across this country, daily issue permits for septic systems that are destined to fail. The typical Individual Sewage Disposal System (ISDS) Regulations define the design features of a standard septic tank/soil absorption system.

                The codes allow for the single compartment or 2 compartment septic tank to be completely buried, and typically the leach field is either a single gravel filled trench system, or a single gravel filled bed system, also completely buried. There is no above ground evidence as to where the septic tank, and the leach field actually are located once the landscaping has matured.

                The Regulatory Agencies recognize the importance of regular septic sludge removal from the septic tanks, and most REQUIRE sludge removal every 3 to 5 years. This responsibility is placed on the shoulders of the system owner. I guess that the committee which wrote the regulations assumed that septic system owners are going to excavate the soil above the septic tank riser, remove the lid, and contract with a Septic Tank Pumper to remove the septage from the septic tank every 3 to 5 years.

                The maintenance performed on most septic systems in this country is triggered by system failure. This is maintenance by crises. If the systems were designed and installed so that they lend themselves to EASY MAINTENANCE, and if the system owners were provided a System Operation Manual, then perhaps there is a chance in Hell that annual system maintenance would be performed.


                In my view, the minimum design standards for septic tank/soil absorption systems should be changed to take advantage of new technology as it develops, and to construct systems that are easy to locate, and maintain. Existing, inadequately designed systems can be modified to meet new minimum design standards.


                SEPTIC TANK – Install risers to the ground surface from the inlet end access hole of the first septic tank, and the outlet end access hole of the second tank. Septic Tank risers with locking lids are available on the market. Install a Septic Tank Effluent Filter in the outlet tee of the second tank. You may have to replace the outlet tee if the existing outlet baffle is not a 4 inch sanitary tee, or if the tee is not accessable for filter maintenance.

                ALTERNATING LEACH FIELDS – Install a 4 inch plug valve manufactured by National Diversified Sales (NDS)into the septic tank effluent pipeline between the second tank and the existing leach field. Install a new, chamber type leach field which is 50% of the original required leach field area in size. Install monitoring and ventilation ports in each end of the chamber system, and cover the chambers with a 4 foot wide layer of 6 ounce, random fiber geotextile fabric. The fabric prevents siltation of the void under the chambers, and enhances the soil infiltration area of the leach field.

                Divert the septic tank effluent into the new chamber leach field, and allow the existing stone and pipe system to become unsaturated. Excavate the soil above the perforated distribution pipe at 2 locations and install 4 inch tees to provide for monitoring and ventilation ports for the existing leach field. Install 4 inch S&D Female Adapters on the top of the riser pipes so that the top of the caps are about 3 inches below the final grade. Install 6 inch irrigation valve boxes over all of the leach field risers. Solid, threaded plugs are placed in the risers from the “In-Use” leach field to prevent sewer gas odors from emanating into the yard. The “Resting” leach field risers are fitted with 4 inch drain grates to allow for atmospheric air, rich in oxygen (21%), to flow into the leach field.


                Annual maintenance duties should be performed on July 4th, “SEWAGE INDEPENDENCE DAY”. Celebrate your independence of the “SEWER GRID”, but recognize that with this independence comes the responsibility of a Septic Tank System Operator.

                Measure the sludge depth in the fist compartment of the septic tank system. When the very black, indigestible septic tank sludge accumulates to a depth equal to 1/3 the liquid depth of the tank, then it is time to remove the sludge.

                Remove the lid on the outlet end of the second septic tank and raise the septic tank effluent filter to the top of the sanitary tee which is the outlet baffle. Flush the organic debris, and biological slimes which have accumulated on the filter with the strong stream of a garden hose back into the tank. Reset the filter into the outlet tee, and replace the lid.

                Remove the lid from the diversion valve. Lift the plug valve about 6 inches, and turn the plug 90 degrees, and then reset the plug. This procedure results in diverting the septic tank effluent to the alternate leach field.

                Exchange the solid threaded plugs, and the drain grates on the leach field risers.

                Record the annual maintenance practices which you have performed in a maintenance log which is contained in an operation manual. This manual will be quite valuable when the property is placed for sale in the future.

                Well Jeff, I had better end this diatribe. I probably have told you more than you wanted to know, but if you require more information, send me an e-mail. JWA

                [Edited by John Aldrich on 09 August 2001]
                [Edited by John Aldrich on 10 August 2001]

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