2.0 SYSTEM DESIGN
© Presby Environmental, Inc., Design & Installation Manual, July 2020 Edition
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Illustration of Design Example #3 (units separated to avoid site obstacle):
Note: Many alternative layouts could have been used.
2.3 Design Specifications
The system shall be designed in accordance with this Manual and state rules and can be installed using either bed
or trench design utilizing any of the design configurations outlined in this Manual.
Daily Design Flow (DDF)
Residential DDF for EF systems is calculated in accordance with state rules. Systems servicing more than two
residences shall use the commercial specifications detailed in the sizing tables. The minimum DDF shall be one
bedroom for any single-family residential system and 300 gpd for any commercial system.
Septic Tank
The system is designed to treat effluent that has received “primary treatment” in a standard septic tank. Septic
tanks shall be sized according to state/local rules. All septic tanks must be equipped with baffles to prevent excess
solids from entering the EF system. When a Remediator is designed and installed with an EF system, all minimum
septic tank sizing requirements listed in Env-Wq 1010 must be met independent of, and without respect to, use of
the Remediator.
Water Purification Systems
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Water purification systems and water softeners should not discharge into any EF system.
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If water purification systems or water softeners must be discharged into the EF system, then the EF
system will need to be “oversized.” Calculate the total amount of backwash in gpd, multiply by 2, and add
this amount to the DDF when determining the septic tank and EF drainfield area sizing.
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Water purification systems and water softeners require regular routine maintenance; consult and follow
the manufacturer’s maintenance recommendations.
Pressure Distribution
The use of pressure distribution lines in the EF system is prohibited. Pumps may be utilized when necessary only
to gain elevation and to feed a D-box which then distributes effluent by gravity to the EF units. Siphon dosing is
permitted; adequate venting is required in a siphon-dosed system or pumped system, which may require an
additional high vent (referred to as “differential venting”).
Effluent (Wastewater) Strength
Design specifications for use of the EF system are based on residential strength effluent, which has received
primary treatment in a septic tank. Designing a system that will treat higher strength wastes requires additional EF
units. In these situations, our Technical Advisors shall be consulted for recommendations at (800) 473-5298.