1. Michael A. Schwartz, P.E.
Time Dose vs. “Pump & Dump”

2. This is what we want to avoid, right!?

3. So here’s what we’ll learn about:
Basic System Layout
Operations
Major Components of Each System
•Identify differences for each system
•Design criteria (engineering standpoint)
•Examples
Field Example - Conversion

4. Background
• Major Components of a Traditional Gravity System
• Septic Tank • Drain field (Disposal Area)
• Distribution Box

5. Background
• Major Components of a Pump System
• Septic Tank • Pump
• Dose Chamber • Drainfield (Disposal Area)

6. Types of Pump Systems

7. “Pump & Dump”
• Septic Tank • Raised or at Grade
• Dosing Chamber • Traditional Trench or Bed
• Pump • Containing 4” PVC Diameter
• Conventional Disposal Area Laterals (Non-pressurized)
Types

8. Time Dose
• Septic Tank • Traditional Trench or Bed
• Dosing Tank • Containing Small Diameter
• Pump Laterals (1”-2”)
• Conventional Disposal Area • Lateral with Orifices (small holes)
• Raised or at Grade • Pressurized System
Types

9. Typical Trench Cross-Section
Types

10. Float Operation Comparison
“Pump & Dump” Time Dose
• Float 1 – High Water • Float 1 – Lag Pump –
Alarm Timer Over-Ride (HWA)
• Float 2 – Lag Pump On • Float 2 – Lead Pump -
• Float 3 – Lead Pump On Timer Over-Ride (HWA)
• Float 4 – Pumps Off • Float 3 – Pumps Off /
• Float 5 – Redundant Timer Enable
Off / Low level Alarm • Float 4 – Redundant
Off / Low level Alarm

11. Major Components

12. Septic Tank
• Remains the same size for the 3 systems
• Traditional Gravity
• Pump & Dump
• Time Dose Septic Tank
• Sizing is currently based on hold time
Major Components Dosing Tank
• 24-hours or 72-hours (food service)
• Exception (minimal size –typically 1,000 Pump
gals)
Disposal Area
• Purpose – Pretreatment (separate - solids,
FOG, liquid)
Major Components

13. Septic Tank
• Example #1
• 2,400 gallons per day
• Non-Food Service Establishment
• Loamy Sand Septic Tank
• Typically perform topographic and
Dosing Tank
boundary survey, soils evaluation and flow
determination to determine constraints
Pump
• Septic Tank Size = 24-hour flow
• Therefore minimum tank size = 2,400 Disposal Area
gallons
Major Components

14. Major Components
“Pump & Dump”:
Dose Tank & Pump

15. “Pump & Dump”
• Sizing
• Dosing Chamber
• The liquid capacity of the dosing tank must
be sufficient to dose the soil absorption
Septic Tank
field or bed no more than three (3) to four
(4) times a day at design flow.
Dosing Tank
• Pump
• Pumps should be sized to empty the dosing Pump
tank in no more than 20 minutes.
• Automatic alternating pumps shall be Disposal Area
provided in all systems where design flow
exceeds 2,000 gallons/day and in locations
where continuous reliability is essential.
Major Components

16. “Pump & Dump”
• Example #2
• 2,400 gallons per day
• Non-Food Service Establishment
• Loamy Sand Septic Tank
• Since Flow > 2,000 gallons per day, design
Dosing Tank
system with 2 pumps
Pump
Disposal Area
Major Components

17. “Pump & Dump”
• Example #3
• 2 Pumps to 1 Disposal Area
• Dose Chamber = 2,400 / 3 = 800 gal
• Dose Chamber = 2,400 / 4 = 600 gal Septic Tank
• Dosing Tank Size = 1,000 gallon – 1,200
Dosing Tank
gallon
Pump
Disposal Area
Major Components

18. “Pump & Dump”
• Example #4
• 2 Pumps to ½ of the disposal area each
• Dose Chamber = 2,400 / 6 = 400 gal
• Dose Chamber = 2,400 / 8 = 300 gal Septic Tank
• Dosing Tank Size about 500-750 gallon
Dosing Tank
Pump
Disposal Area
Major Components

19. “Pump & Dump”
• Example #5
• Pumps should be sized to empty the
dosing tank in no more than 20 minutes.
• 300 gallons / 20 minutes = 15 gpm Septic Tank
(minimum)
• Pumps need 2 items to specify Dosing Tank
• GPM
Pump
• TDH (Total Dynamic Head)
• TDH = Static Lift + Friction Lost Disposal Area
• Friction Loss also known as “head lost” is
divided into two main categories, "major
losses" associated with energy loss per
length of pipe, and "minor losses"
associated with bends, fittings, valves, etc.
Major Components

20. Major Components
“Pump & Dump”:
Disposal Area

21. “Pump & Dump”
• Disposal Area Sizing
• Absorption systems shall be sized on the
basis of the maximum daily sewage flows,
according to the following table:
Septic Tank
Dosing Tank
Pump
Disposal Area
Major Components

22. “Pump & Dump”
• Example #6
• 2,400 gallons/day
• Non-Food Service Establishment
• Loamy Sand Septic Tank
• Assuming a trench layout:
Dosing Tank
• Loamy Sand = 0.75 gal per day / square
foot Pump
• 2,400 g.p.d. / 0.75 g.p.d./sq.ft. = 3,200 sq.
ft. Disposal Area
Major Components

23. “Pump & Dump”
• Example #7 – Network Layout
• 3,200 sq. ft. bottom area required
• Assume trench is 3’ wide: 3,200 / 3’ =
1,070 LF of trench required Septic Tank
• Probably use 12 trenches that are 90 feet
long x 3’ wide with 4’ undisturbed earth Dosing Tank
between trenches.
Pump
• With 2 pumps, each pump would
discharge to 6 of the 12 trenches. Disposal Area
Major Components

24. Time Dose

25. Time Dose
• Septic Tank • Traditional Trench or Bed
• Dosing Tank • Containing Small Diameter
• Pump Laterals (1”-2”)
• Conventional Disposal Area • Lateral with Orifices (small holes)
• Raised or at Grade • Pressurized System
Major Components

26. Time Dose
• Why Time Dose?
• Pressure distribution is a recent modification to the
conventional dosed sewage system. Uniform distribution
over the bottom area of the drain field is achieved and
provides certain advantages over conventional systems as
follows:
1. Formation of the clogging mat is substantially delayed.
2. System provides for unsaturated flow into underlying soil.
3. System design is not limited to rectangular configuration.
Major Components

27. Time Dose
• Why Time Dose?
Same Different
Septic Tank x
Conventional Disposal Area x
Raised or at Grade x
Traditional Trench or Bed x
Containing Small Diameter Laterals (1”-2”) x
Lateral with Orifices (small holes) x
Pump x
Dosing Tank x
Major Components

28. Time Dose
• Order of Design
• Septic Tank – Same (based on retention time)
• Disposal Area Network
• Orifices (small holes) – Spacing & Size
• Laterals Diameter
• Pump
• Dosing Tank
Major Components

29. Major Components
Time Dose:
Disposal Area

30. Time Dose
1. Configure Disposal Area Network
2. Determine Length of Lateral
• Example: 2,400 gallons per day, Non-Food
Service Establishment, Loamy Sand Septic Tank
• Assuming a trench layout:
• Loamy Sand = 0.75 gal per day / sq. foot Disposal Area
• 2,400 g.p.d. / 0.75 g.p.d./sq.ft. = 3,200 sq. Pump
ft.
• Assume trench is 3’ wide: Dosing Tank
• 3,200 / 3’ = 1070 LF of trench required
• Use 12 trenches that are 90 feet long x 3’
wide with 4’ undisturbed earth between
trenches
Major Components

31. Time Dose
3. Determine “orifice” spacing and size
• Michigan Criteria for Subsurface Sewage Disposal
reference “Pressure Distribution Network Design
Manual,” Technical Guide for Pressure Mound Systems
(June 2003 MDEQ)
• Pressure distribution system design should generally comply with Septic Tank
currently accepted design practice including the following features:
• Design shall provide uniform doses with no more than 0.5 gallons
per orifice per dose.
Disposal Area
• Distribution cell area per orifice shall not exceed 12 sq.ft.
• To reduce orifice plugging, high head pumps are recommended. Pump
• Orifice shields should be provided.
• Provisions for flushing must be incorporated at the ends of all
laterals. Dosing Tank
• Geotextile fabric which prevents the downward migration of fine
materials but allows for free passage of air and water should be
placed over the stone in the distribution cell prior to placement of
final cover.
Major Components

32. Time Dose
3. Determine “orifice” spacing and size
• Distribution cell area per orifice shall not
exceed 12 sq.ft.
• Spacing is typically 3-5 feet apart (some
Septic Tank
health department code books dictate
spacing. Disposal Area
• If the trench is 3’ wide and each orifice is
to “distribute” effluent to 12 sq.ft. than Pump
spacing is 4’ apart
Dosing Tank
Major Components

33. Time Dose
3. Determine “orifice” spacing and size
• Orifice sizes can range from 1/8” diameter
to 5/8” diameter.
• Typically 1/8”, 3/16” or 1/4” diameter Septic Tank
• 3/16” diameter is most common sized
used Disposal Area
• Larger holes will be problematic on finding
Pump
a pump to produce adequate design flow
• Some health departments provides Dosing Tank
recommended size
• Ultimately up to the design engineer
Major Components

34. Time Dose
4. Determine lateral pipe diameter
Septic Tank
Disposal Area
Pump
Dosing Tank
Want the 1st orifice to distribute approximately equal to the last
orifice (this table is for 3/16” orifices)
Major Components

35. Time Dose
5. Determine Number of Orifices/Lateral
• # of orifices = Length of Lateral / Spacing
of orifice
• Example: 90 ft lateral / 4 ft spacing = 23 Septic Tank
orifices
Disposal Area
Pump
Dosing Tank
Major Components

36. Major Components
Time Dose:
Pump

37. Time Dose
6. Determine Lateral Discharge Rate
Septic Tank
Disposal Area
Pump
Dosing Tank
If 3/16” orifice with 4 ft pressure = 0.83 gal/orifice
23 orifice / lateral x 0.83 gal/orifice = 19.09 gal/lateral
Major Components

38. Time Dose
7. Determine Network Discharge Rate (zone)
• Determine how many laterals are in the
network (per pump or zone) and multiple
by GPM per lateral
Septic Tank
• 12 trenches (laterals) with each pump
utilizing 6 laterals each (network has 2 Disposal Area
zones)
• 6 laterals x 19.09 gal / lateral = 114.5 gpm Pump
• This is the minimum pump flow required Dosing Tank
Major Components

39. Time Dose
• Pump Comparison Sizing
• Pump & Dump”
• 20 minutes to empty septic tank
• Time Dose Septic Tank
• # of orifices (more orifices = more gpm)
• Size of Orifices (larger orifices = more gpm) Disposal Area
• Spacing of orifices (closer space = more
Pump
gpm)
• Example: 15 gpm vs. 114.5 (6 – 90’ Dosing Tank
trenches per pump)
• Each on is dosing 1,600 sq ft of area
• “Pump & Dump” = 20 minutes
• Time Dose = very short timeframe
Major Components

40. Time Dose
8. Calculate Manifold Size
9. Determine the Total Dynamic Head
• TDH = Static Lift + Friction Lost +
Perforation Head Septic Tank
• Perforation head = 1.3(Q/(11.79*d^2))^2
Disposal Area
• Perforation head = 1.3(squirt height)
10. Select Pump Pump
• Pumps need 2 items to specify (GPM &
Dosing Tank
TDH)
• Repeat if necessary
Major Components

41. Major Components: Time Dose
Pump Curve

42. Major Components
Time Dose:
Dose Chamber

43. Time Dose
11. Determine Dose Volume
• Technical Guide for Pressure Mound
Systems (June 2003 MDEQ)
• Design shall provide uniform doses with no
Septic Tank
more than 0.5 gallons per orifice per dose.
• Example: 6 laterals with 23 orifices per Disposal Area
lateral = 138 orifices
• 138 orifices x 0.5 gal per orifice dose rate = Pump
69 gals per dose
Dosing Tank
Major Components

44. Time Dose
12. Calculate Run Time of Pump
• Run Time = (Dose Volume + “Empty” Pipe
Volume) / Pump Rate
• Example: Septic Tank
• Dose Volume = 69 gallons
• Volume to “fill” pipe = 17 gallons Disposal Area
• Pump Rate = 114.5 gpm
Pump
• Run Time = (69 gal +17 gal) / 114.5 gpm =
0.75 minutes = 45 seconds Dosing Tank
Major Components

45. Time Dose
13. Calculate Number of Doses/Day
• Gallons per day = 2,400
• Gallons per dose = 69
• Doses per day = 2400 / 69 = 34 doses Septic Tank
• Therefore each pump will operate 17
Disposal Area
times per day
Pump
Dosing Tank
Major Components

46. Time Dose
• Calculation Check
• Dose = 0.5 gallons / dose / orifice
• # of doses per day = 17
• Gallons per day / orifice = 8.5 gallons Septic Tank
• Soil Load Rate 0.75 gal/sq. ft.
Disposal Area
• Each orifice is dosing 12 sq. ft.
• Dose < 0.75 gal/sq. ft. x 12 sq. ft. = 9 Pump
gallons
Dosing Tank
• Numbers check
Major Components

47. Time Dose
14. Calculate Programmable Timer Settings
• Previous step determined number times a
pump turns on (34 times)
• If want to equal dose over 22 hours Septic Tank
(account for peak days)
• Duration is up to the design engineer Disposal Area
• 22 hours x 60 min/hour = 1320 minutes
Pump
• 1320 minutes / 34 times = 38.8 minutes
• Therefore a pump will run 45 seconds and Dosing Tank
no pump will run for 38 minutes
• (76 minutes off time per pump)
Major Components

48. Time Dose
15. Size the Dose Chamber
• Up to the judgment of the engineer
• Based on off time and timing of incoming
flow Septic Tank
Disposal Area
Pump
Dosing Tank
Major Components

49. System Conversion

50. • Conversion of a “Pump & Dump” to a Time Dose System
• Flushing Elementary, Flushing, MI
System Conversion

51. Existing Drain Field
System Conversion

52. Drawing
System Conversion

53. Existing Septic Tank /Pump
Chamber
System Conversion

54. Existing Septic Tank /Pump
Chamber
System Conversion

55. Existing Septic Tank /Pump
Chamber
System Conversion

56. Existing Septic Tank /Pump
Chamber
System Conversion

57. Proposed Drain Field
System Conversion

58. System Conversion

59. System Conversion

60. System Conversion

61. Construction
System Conversion

62. Construction
System Conversion

63. System Conversion

64. System Conversion

65. Construction
System Conversion

66. Construction
System Conversion

67. System Conversion

68. System Conversion

69. Construction
System Conversion

70. Construction
System Conversion

71. Construction
System Conversion

72. Construction
System Conversion

73. Final Site Photos
System Conversion

74. Final Site Photos
System Conversion

75. Thank you.
Do You Have Questions?
E-mail Mike:
Michael A. Schwartz, P.E.
mschwartz@preinnewhof.com