US3545617A - Precast septic tank - Google Patents

Description

United States Patent [72] Inventor Wellington Hamrick P.0. Box 755, Boiling Springs, North Carolina 28017 [21] Appl. No. 742,237 [22] Filed July 3, 1968 [45] Patented Dec. 8, 1970 [54] PRECAST SEPTIC TANK 5 Claims, 4 Drawing Figs.

[52] [1.8. CI. 210/109, 210/123, 210/532 [51] Int. Cl..., B01d 21/02 B01d 21/24 [50] Field otSearch 210/109, 115,123, 532, 532(8) [56] References Cited UNITED STATES PATENTS 1,422,674 7/1922 Cook 210/532(S) 2,078,260 4/1937 Mallory 210/532 2,401,067 5/1946 Granberg 210/115 2,412,785 12/1946 Torricelli 210/532 2,792,125 5/1957 Gallacher..... 210/532(S) 3,275,157 9/1966 Stamps 210/532X F OREIGN PATENTS 490,267 12/1926 Germany 210/123 807,639 1/1959 Great Britain 2lO/532(S) Primary Examiner Reuben Friedman Assistant Examiner- C.M. Ditlow Att0rney-Parrott, Bell, Seltzer, Park and Gibson PRECAST SEPTIC TANK This invention relates generally to a septic tank and more particularly to septic tanks of the type which are formed of precast concrete and the like.

Precast septic tanks usually include integrally cast side, end, and bottom walls with one or more vertical baffles extending between the sidewalls to provide separate compartments in the tank. A cover is formed of a plurality of slabs which extend across between the sidewalls and form an upper wall therein. The waste material enters atthe inlet end of the tank and is discharged through an outlet opening which-is positioned at a slightly lower elevation than the inlet opening. The discharged waste material normally passes into a separate distribution box and from there it is directed to the individual septic tank lines of the septic tank field. While the usual-type of vertical baffles are intended to prevent the discharge of the sludge precipitate and to permit the discharge of liquid waste, they have not been completely effective for the desired purpose.

Several different types of discharge limiting devices have been proposed to prevent the discharge of sludge through the outlet of the septic tank, However, these proposed devices have not been widely used because they are either too expensive and complicated to' construct and install or they require frequent maintenance and repair.

With the foregoing in mind, it is an object of the present invention to provide an improved precast septic tank which is simple to assemble and 'instalLand which requires little or no maintenance except the usual sludge removal. To this end, the tank has an internal distribution and separationchamber at the discharge end and is provided with elongate upper and lower tank halves which are cast in such a manner as to easily fit together and to properly support the baffle walls forming one side and the bottom of the internal distribution and separation chamber.

It is a further object of the present invention to provide an improved outlet control means for the internal distribution and separation chamber to readily permit the discharge of fluid waste from the tank, but to prevent the discharge of sludge therefrom. The outletjcontrol means is in theform of a float valve which operates when the level of the sludge in the tank reaches the level of the bottom of the distribution chamber. v

Some of the objects of the invention having been stated, otherobjects will appear as the description proceeds when taken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of the septic tank of the present invention; g

FIG. 2 is a longitudinal vertical sectional view taken substantially along line 2-2 in FIG. 1;

FIG. 3 is a transverse vertical sectional view taken substantially along the line 3-3 in FIG. 2; and

FIG. 4 is an enlarged sectional view of that portion of the central right-hand portion of FIG. 2 which is enclosed by the dotted circle 4 and illustrating the manner in which the front edge of the horizontal baffle wall is supported at the juncture of the upper and lower halves of the tank.

Generally, the precast septic tank of the present invention includes elongate upper and lower tank halves, broadly indicated at and 11 which are each substantially alike. The upper half 10 includes substantially vertical end walls 12, 13 and substantially vertical sidewalls 14, 15 which are cast integral with the endwalls and with a horizontal top wall 16. The lower tank half 11 also includes endwalls 18, 19, and sidewalls 20, 21 which are cast integral with the endwalls and with a horizontal bottom wall 22. The side and endwalls of each tank half are slanted outwardly a very slight amount to facilitate removal from the mold forms.

At one end of the tank, which will be referred to as the inlet end, a sewage inlet pipe 23 extends through a suitable inlet opening 24 in the end wall 12. Suitable knockout ports 25 (FIG. 1) are provided in the sidewalls 14, 15 in the event it is necessary or desirable to bring the inlet pipe 23 into the tank from either side. One end of an outlet pipe 27 is supported in a suitable opening 28 in the end wall 13 and the other end of the pipe 27 is connected to the usual drainage lines, not shown, of the septic tank field. Suitable knockout ports 29 (FIG. 1) are also provided in the sidewalls 14, 15 and the end wall 13 so that the discharge pipe 27 may be connected at either side of the septic tank and so that additional drainage lines may be connected to the discharge end of the tank, should it be necessary.

Inspection openings with inwardly slanting sides are cast in the top wall 16 and are closed by mating removable covers 30 which may be provided with lifting handles 31. The knockout ports 29 and the outlet pipe 27 are positioned at a slightly lower level than the inlet knockout ports 25 and the inlet pipe 23 to facilitate passage of the liquid sewage through the tank and into the septic tank field. As illustrated in FIG. 2, sewage is discharged into the interior of the tank from the inlet pipe 23 and the solids are subjected to bacterial action to form a relatively heavy layer of sludge as a precipitate, indicated at 32 in the lower portion of the lower tank half 11. The remainder of the tank, up to the level of the outlet pipe 27, is substantially filled with a relatively sludge-free liquid waste. The lower peripheral edge of the upper tank half 10 and the upper peripheral edge of the lower tank half 11 are joined together in mating relationship to prevent leakage of the liquid from the tank. As shown in FIG. 2, the upper peripheral edge of the walls of the lower tank half 11 is provided with a V- shaped groove which mates with a V-shaped tongue on the lower peripheral edge of the walls of upper tank half 10. A suitable sealingcompound is preferably placed between the peripheral edges when the two halves are joined together to prevent leakage.

When the lower half 11 is cast, the inner portion of the V- shaped groove is omitted along the end wall 19 and along the front portions of the sidewalls 20, 21 to provide a support shelf for a horizontal baffle wall 35 which forms a portion of an internal distribution and separation chamber broadly indicated at 40. The forward portions of the sidewalls 14, 15, the forward portion of the top wall 16, and the endwall 13 define the respective side, top and forward walls of the chamber 40. The distribution andseparation chamber 40 also includes a vertical baffle wall 41 which extends between the sidewalls 14, 15

and its oppositeside edges are supported in grooves or slots 42, 43 (FIG. 1) formed in the respective sidewalls 14, 15. As

shown in FIG. 2, the upper edge of the vertical baffle wall 41 terminates slightly below the lower level of the top wall 16 and the lower edge rests upon and is supported by the rear edge portion of the horizontal baffle wall 35. The front edge and opposite side edges of the baffle wall 35 are beveled downwardly, as shown in FIG. 4, to fit into the groove formed by omission of the inner portion of the V-shaped groove in the upper edge of the forward end of the lower tank portion 11. Thus, the horizontal baffle wall 35 is supported at the level of the juncture of the peripheral-edges of upper and lower tank halves 10, 11 and its rear edge supports the vertical baffle wall '41. A circular opening 44 is provided in the center of the horizontal baffle wall 35 to permit liquid to enter the distribution and separation chamber 40 so that the liquid level is maintained at the same level throughout the tank. The walls 35, 41 define respective bottom and rear walls of the chamber 40.

During normal operation of the tank, the heavy sludge 32 precipitates to the bottom of the lower tank 11 and will not rise into the distribution and separation chamber 40 so that it is not discharged into the septic tank field where it could clog the lines and prevent drainage in the field. However, with continued use of the septic tank, the level of the sludge precipitate 32 will rise in the tank and could eventually reach such a level in the separation chamber 41 that it might pass through the outlet pipe 27 and into the drainage lines of the septic tank field.

In order to prevent the heavy sludge 32 from rising and passing through the opening 44 and into the chamber 40, a

float valve type closure may be provided in the opening 44. The float valve closure includes a float member 46 suitably attached to the lower end of a stem 47 which extends through the opening 44 and its upper end is connected to cross support members 50. The float member 46 is heavy enough that it is not sufficiently buoyant to be raised by the sludge-free liquid 21 in the tank and the opening 44 remains open so that the liquid may pass into the separation chamber 40. However, when the level of the sludge 32 rises to the level of the float 46, the relatively heavy sludge will raise the float 46 to close the opening 44 and prevent the passage of the relatively heavy sludge into the compartment 40.

When the float 46 covers the opening 44, the liquid level in the tank will rise and back up in the system connected to the inlet pipe 23 so that the users of the system will know that the level of the sludge has reached the point that the tank must be pumped out. Even without the float valve closure, only a limited amount of heavy sludge will pass into the distribution and separation chamber 40 as the level reaches the level of the bottom of the chamber because the opening 44 is relatively small, as compared to the remaining area in the tank. If desired, several openings may be provided in the wall 35 of the chamber 40 and a float valve closure may be provided in each.

In the drawings and specification there has been set forth a preferred embodiment of the invention and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

lclaim:

l. A precast septic tank comprising:

a. elongate upper and lower tank halves, said upper and lower tank halves each including:

1. substantially vertical end and side walls cast integral with each other and with horizontal walls defining top and bottom walls of said tank;

2. said end and side walls of said tank halves each including peripheral edges joined together in mating relationship;

3. at least one inlet opening at one end of said upper tank half; and

4. at least one outlet opening at the other end of said upper tank half; and

b. an internal distribution and separation chamber at said other end of said upper tank half, said end wall and portions of said side and top walls of said upper tank half defining the forward, side and top walls of said chamber,

said chamber including:

1. a vertical baffle wall extending between said side walls of said upper tank half and having a lower edge terminating at the juncture of said peripheral edges of said tank halves and defining a rear wall of said chamber;

2. a separate and removable horizontal baffle wall extending between said sidewalls and said end wall and being supported on the lower tank half and at the juncture of said peripheral edges of said tank halves, said horizon tal bafile wall extending beneath said lower edge of said vertical baffle wall and supporting the same, and said horizontal baffle wall defining a bottom wall of said chamber; and

. said horizontal baffle wall having an opening therein to permit fluid to rise in said chamber and pass out the outlet opening at said other end of said upper tank half.

2. A septic tank according to claim 1 wherein vertical slots are cast on the inner surfaces of said sidewalls of said upper tank half, and said vertical bafile wall having opposite sides supported in the slots of said sidewalls.

3. A septic tank according to claim 1 wherein said peripheral edges of said upper and lower tank halves respectively comprise a V-shaped tongue and a mating V-shaped groove, said horizontal baffle wall including outwardly beveled side and front edges, and the inner portion of said V- shaped grooves of corresponding portions of said side and end walls bein omitted to rovide a support led e on which said side and rent edges 0 said horizontal ba e wall are supported.

4. A septic tank according to claim 1 including valve means associated with the opening in said horizontal baffle wall; said valve means being so constructed and arranged to permit passage of liquid waste therethrough and to prevent passage of heavy sludge therethrough.

5. A septic tank according to claim 4 wherein said float valve control means includes a float, and means normally supporting said float in spaced relationship beneath the opening in said horizontal baffle wall, said float having a buoyancy such that said float will rise in the level of sludge in said tank I and will not rise in the liquid waste in said tank, and wherein said float valve control means includes valve means to close the opening upon sufficient rise in level of said float.

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