|GreenLeach - Enhanced Filtration
Systems - Frequently Asked Questions
What is a GreenLeach Filter?
It is an environmentally friendly leaching system product that is
very effective in allowing liquid discharged from a septic tank or sewage
treatment system to be adsorbed and dispersed into soil. When effluent is
discharged to the center core, the liquid leaving the core and sidewalls of the
numerous fins passes through a filter fabric. This fabric provides a stable
platform for the biological mat to quickly form, thus providing added effluent
treatment through the mat and the fabric.
How is the product shaped and why?
GreenLeach Filter is designed as a linear leaching system
consisting of a 12” gravel filled center core that runs the length of the trench
and 4” wide gravel filled leaching fingers extending off both sides. The fingers
are 25” long with 4” of porous sand backfill placed on the outside of the fabric
in between each finger. Cardboard is used as a temporary form to hold the
fabric-covered fingers in place until construction is completed. The cardboard
will degrade in time with moisture and effluent application, leaving the gravel
in contact with the filter fabric and sand. The product was designed in this
manner to maximize the area for growth of a biological mat (bio mat) while still
maintaining an aerobic atmosphere in the sand backfill placed on the outside of
the fingers. The resultant product permits more leaching area to be installed in
a smaller area, thus saving on system installation.
Why use so many plastic finger spacers on top?
Product stability during installation is a critical factor. The
patented spacer and disposable gravel chute system hold the core and fingers
rigid during the entire gravel placement and sand backfill process. The leaching
fingers do not deform thereby allowing easy spreading of ¾” gravel to the finger
ends and likewise, sand between the fingers. The spreaders can be removed when
the product stabilized with gravel in place and some sand spread in between the
fingers. The chute is easily removed upon completion of gravel placement.
Can all GLF units be used beneath parking lots?
The GreenLeach Filter units fall into the same category as
standard gravel trenches which have been used beneath parking lots for decades
so the answer is a definite YES! The 4” diameter PVC pipe is totally encased by
the ¾” stone. Gravel placed inside the form does not compact at all and sand
used to backfill the fingers is compacted as part of the installation. Once
properly installed, nothing will settle and the 4” diameter PVC distribution
pipe remains stable. The distribution pipe will be subjected to heavier than
normal loads so use of heavy duty perforated ASTM D3034 SDR 35 pipe is
recommended. The CT Public Health Code requires a minimum of 2” of gravel
(stone) above the pipe to totally encase the pipe in a protective stone case.
The Code also requires a minimum of 6” soil cover above the stone. For parking
lots, the minimum recommended cover above the top of the pipe should be
increased to a total of 12” of stone, sand & gravel, processed gravel or some
combination of the three. The added soil cover reduces the pressure on the
distribution pipe and the added wall thickness of the SDR 35 pipe assures the
channel remains round. Similar care must be given to the solid distribution pipe
used between the GLF and the septic tank. Either specify use of ASTM D 1785
Schedule 40 if no bedding (stone) is to be provided or use the SDR 35 bedded in
stone as described above including the 12” stone/soil cover. No cast iron or
ductile iron pipe can be used after the septic tank. If small diameter pressure
distribution pipe is placed in stone on top of the GLF, there is less concern
for crushing due to the increased strength and wall thickness of the small
(1-2”) diameter water pressure pipe. Based upon years of experience with all
leaching systems, the standard 2” stone cover and 6-8” of additional process
cover would be adequate to protect the pipe.
Can filter fabric be placed beneath the
GreenLeach Filter? In environmentally sensitive
areas, it may be advisable to add the extra filtering benefit by placement of
filter fabric beneath the trench. All new septic systems constructed in soils
allow a higher rate of pollutants to escape the system until formation of a
stable biological mat (bio mat). The fabric will help form a mat more quickly
but will result in a slight reduction in credited effective area (0.4 SF/LF)
based upon the CT DPH rating criteria. The 6” depth of select sand fill required
beneath every GreenLeach system constructed also provides efficient filtration
prior to effluent reaching the natural soils.
What are some physical differences between
the GreenLeach Filter and some other common leaching systems?
All leaching systems allow effluent to leach into the surrounding
soils using various media and methods. Many hollow chambered structures use
direct soil application, may use gravel backfill, employ filter fabric covering
or have slotted/perforated sidewalls to facilitate liquid transfer to the soil.
Common gravel trenches use clean gravel to provide voids for effluent storage
and are constructed with gravel directly contacting the soil on the bottom and
sides. Some specialty products use styrene or rubber tire chips to imitate
gravel. The GreenLeach Filter is slightly different in that it uses 4 inch wide
filter fabric covered fingers that are specifically backfilled on the outside
with washed concrete sand (or naturally sandy, permeable soils) and the ¾ inch
gravel placed on the inside of the fingers provides structure to keep the fabric
in place, prevents the fingers from collapsing during construction, protects the
distribution pipe and distributes surface loads placed on the system. The gravel
provides internal liquid storage to assist with peak flow storage and
How does the GreenLeach Filter stack up
against other systems? The GLF excels in providing
effluent contact area between the fabric/gravel product and the sand backfill on
the sides and bottom. The GLF provides wetted contact area between the sand and
filter fabric area as shown below: (NOTE-THIS IS PHYSICAL CONTACT AREA
BETWEEN EFFLUENT AND SURROUNDING SOIL ONLY)/b>
GLF 12-62 17.6 square feet per lineal foot of product
GLF 15-62 21.15 "
GLF 18-62 24.8 "
GLF 21-62 28.45 "
GLF 24-62 32.0 "
GLF 27-62 34.75 "
GLF 30-62 38.3 "
GLF 33-62 41.95 "
GLF 36-62 45.7 "
· The Infiltrator (trade mark) Equalizer (16” high x 34” wide) chamber
provides about 6.0 square feet per lineal foot contact area (bottom and sides)
with the soil when placed in a trench.
· A standard 3-foot wide, 18’ deep gravel trench with 12” of gravel
beneath the pipe provides about 5.0 square feet per lineal foot contact area
with the soil.
· A 48” wide, 12” high concrete gallery installed in a 6’ wide trench
using 12” of gravel on the gallery sides provides about 7.5 square feet per
lineal foot contact area with the soil.
Comparison with these three and many other leaching systems clearly show the
advantages to using the GreenLeach Filter as a means to provide effective
leaching area in a compact space. Do the math with any other system and you too
will see how effective the GLF actually is. &
Why do the CT ratings and actual soil
contact areas shown above differ? The CT State
Health Department uses a mathematical formula to give credit to all types of
leaching products and takes into consideration the bottom and vertical leaching
interfaces as well as the type of effluent-soil contact (direct as with chamber
bottoms, gravel, fabric, etc.). They also include a safety factor which is why
the “wetted perimeter” of a gravel trench with a 3’ wide bottom and 12” below
the invert actually has 6 square feet of contact area yet is rated at only 3
square feet per linear foot.
What does the difference in square
footage contact area mean to an engineer or installer who is designing a septic
system to serve a 4-bedroom home? If the State,
County or Local Health Department regulations called for installation of 2 rows,
85 feet long (170’ total) of a hollow plastic chambered system, 16” high, 34”
wide, then replacement by the GreenLeach Filter would substantially reduce the
length of trench installation depending upon the height of GLF used. Using the
GLF 18-62 (18” high), about 41 feet of product would be necessary to provide the
same soil contact area. In CT where safety factors are incorporated in product
ratings and variables are used for various soil interface types, the leaching
product rating formula would equate the 150’ plastic chamber system to about
60.3 feet thereby significantly reducing the area required for system
installation. This is a critical factor for repairs on small lots or on
properties that may contain only pockets of suitable soil. If site conditions
were not restricted by groundwater, ledge rock, hydraulic limitations or
impervious soil conditions, use of the GLF 36-62 could further reduce trench
lengths down to 33 feet of product using the conservative CT rating system. The
GLF does require more labor during installation but the rewards are very
Contact us for a listing of experienced s in your area.