© Presby Environmental, Inc., Maine Design & Installation Manual, June 2019 Edition -18-
30.5 Velocity Reduction
The rate at which effluent enters the AES and ES pipe must be controlled. Excessive effluent velocity can disrupt
solids that settle in the pipes.
a) Effluent must never be pumped directly into AES or ES pipe.
b) A distribution box or tank must be installed between the pumping chamber and the AES or ES pipe to
reduce effluent velocity.
c) Force mains must discharge into a distribution box (or equivalent) with velocity reducer and a baffle, 90°
bend, tee or equivalent (see illustrations below).
30.6 Dose Volume
a) Pump volume per dose must be no greater than 1-gallon times the total linear feet of AES or ES pipe.
b) Pump dosing should be designed for a minimum of 6 cycles per day.
c) If possible, the dosing cycle should provide one hour of drying time between doses.
30.7 Basic Serial Distribution Limit
Pumped systems with Basic Serial distribution are limited to a maximum dose rate of 40 gallons per minute and do
not require the use of a flow equalizer on the D-box outlet. Never pump directly into AES or ES pipe.
30.8 Combination and Multiple-Bed Distribution Limit
All AES and ES systems with Combination Serial distribution or Multiple Bed distribution must use Flow Equalizers in
each distribution box outlet. Each Bed or section of Combination Serial distribution is limited to a maximum of 20
gallons per minute, due to the flow constraints of the equalizers. Example: pumping to a combination system with 3
sections (using 3 D-box outlets). The maximum delivery rate is (3 x 20) = 60 GPM. Always provide a means of
velocity reduction.
31.0 System Sand and Sand Fill Requirements for All Beds
It is critical to the proper functioning of field that the proper amount and type of System Sand be installed.
31.1 System Sand
System Sand must be clean, granular sand free of organic matter and must adhere to the following percentage and
quality restrictions:
31.2 System Sand Acceptable Alternative
ASTM C-33 (concrete sand), natural or manufactured sand, with not more than 3% passing the #200 sieve (verified
by washing the sample per the requirements of ASTM C-117 as noted in the ASTM C-33 specification) may be used
as an acceptable alternate material for use as System Sand.
31.3 Quantity of System Sand
System Sand is placed a minimum of 3 in. above and 6 in. below and between the pipe rows with a minimum of 6 in.
horizontally around the perimeter of the AES or ES pipes.
31.4 Sand Fill
Sand fill meeting the requirements of CMR 241 Table 11A and is used to raise the elevation of the system in order to
meet the required separation distance from the SHWT or other restrictive feature. No organic material or stones
System Sand Specification
Sieve Size
Percent Retained on Sieve (by weight)
3/4 in. (19 mm)
0
#10 (2 mm)
0 - 35
#35 (0.50 mm)
40 - 90
Note: not more than 3% allowed to pass the #200 sieve (verified by washing sample
per requirements of ASTM C-117)