North Dakota Administrative Code › Title 62 - State Board of Plumbing › Article 62-03.1 - Plumbing Installation Standards › Chapter 62-03.1-03 - Private Sewage Disposal Systems › Section 62-03.1-03-07 - Septic tanks

Current through Supplement No. 393, July, 2024
1.
Liquid
				capacity.
The liquid capacity of all septic tanks shall conform to the
				tables contained in subsection 7 of section 62-03.1-03-03 and this subsection
				as determined by the number of bedrooms or apartment units in dwelling
				occupancies and the occupant load or the number of plumbing fixture units as
				determined from table 7-3 of the Uniform Plumbing Code, whichever is greater,
				in other building occupancies.
CAPACITY OF SEPTIC TANKS *
Single-Family Dwellings - Number of Bedrooms
Multiple Dwelling Units or Apartments - One Bedroom
							 Each
Other Uses -Maximum Fixture Units Served
Minimum Septic Tank Working Capacity in Gallons
1-3
20
1000
4
2
25
1200
5 or 6
3
33
1500
7 or 8
4
45
2000
5
55
2250
6
60
2500
7
70
2750
8
80
3000
9
90
3250
10
100
3500
Extra bedroom, 150 gallons each.
Extra dwelling units over 10, 250 gallons
							 each.
Extra fixture units over 100, 25 gallons
							 per fixture unit.
* NOTE: Septic tank sizes in this table include sludge
				  storage capacity and the connection of domestic food waste disposal units
				  without further volume increase.
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2.
Septic
				tank construction.
Septic tanks must be constructed of sound durable
				materials not subject to excessive corrosion or decay and must be watertight.
				Each such tank must be structurally designed to withstand all anticipated earth
				or other loads and must be installed level and on a solid bed. All tanks
				regardless of material or method of construction must conform to the following
				criteria:
a. The liquid depth of any septic
				tank or compartment shall be not less than thirty inches [76.20 centimeters],
				nor more than six and one-half feet [1.97 meters]. No tank may have an inside
				horizontal dimension less than twenty-four inches [60.96 centimeters].
b. The space in the tank between
				the liquid surface and the top of the inlet and outlet baffles must be not less
				than twenty percent of the total required liquid capacity, except that in
				horizontal cylindrical tanks this space must be not less than fifteen percent
				of the total required liquid capacity.
c. There must be at least one inch [2.54
				centimeters] between the underside of the top of the tank and the highest point
				of the inlet and outlet devices. The inlet invert must be not less than three
				inches [7.62 centimeters] above the outlet invert.
d. Baffles must be integrally cast with the
				tank, affixed with a permanent waterproof adhesive or affixed with stainless
				steel connectors, top and bottom, and be constructed of acid-resistant
				concrete, acid-resistant fiberglass or plastic.
e. The inlet baffle must extend at least six
				inches [15.24 centimeters], but not more than twenty percent of the total
				liquid depth below, the liquid surface and at least one inch [2.54 centimeters]
				above the crown of the inlet sewer.
f. The outlet baffle and the baffles between
				compartments must extend below the liquid surface a distance equal to forty
				percent of the liquid depth, except that the penetration of the indicated
				baffles or sanitary tees for horizontal cylindrical tanks must be thirty-five
				percent of the total liquid depth. They also must extend above the liquid
				surface. In no case may they extend less than six inches [15.24 centimeters]
				above the liquid surface.
g. Inlet
				baffles must be no less than six inches [15.24 centimeters] or no more than
				twelve inches [30.48 centimeters] measured from the end of the inlet pipe to
				the nearest point on the baffle. Outlet baffles must be six inches [15.24
				centimeters] measured from beginning of the outlet pipe to the nearest point on
				the baffle. Sanitary tees used as baffles must be at least four inches [10.16
				centimeters] in diameter.
h. The
				inlet and outlet must be located opposite each other along the axis of maximum
				dimension. The horizontal distance between the nearest points of the inlet and
				outlet devices must be at least four feet [1.22 meters].
i. There may be one or more manholes.
				Manholes must be at least eighteen inches [45.72 centimeters] in diameter, and
				located within six feet [1.83 meters] of all walls of the tank. The manhole
				must extend through the cover to a point within twelve inches [30.48
				centimeters] but no closer than six inches [15.24 centimeters] below finished
				grade. The manhole cover must be corrosion resistant, rated three hundred-pound
				[136.07-kilogram] load bearing, and covered with at least six inches [15.24
				centimeters] of earth. When in the opinion of the administrative authority the
				manhole is permitted above finish grade, it must be safely secured.
j. There must be an inspection pipe of at
				least four inches [10.16 centimeters] in diameter or a manhole over both the
				inlet and outlet devices. The inspection pipe must extend through the cover and
				be capped flush or above finished grade. A downward projection of the
				centerline of the inspection pipe must be directly in line with the centerline
				of the inlet or outlet device.