Abstract:
An apparatus and method for improving the operation of sewer systems includes a first sewer pipe connected to a source of other water and a second smaller diameter sewer pipe passing through the first sewer pipe and connected to sources of sanitary effluent. The second sewer pipe can be attached to the interior surfaces of the first sewer line by a curable adhesive material using a removable inflatable bladder to hold the second sewer pipe in position until the adhesive has cured sufficiently. As an alternative, positioning walls or arms, integral with the second pipe, form positioning spaces filled with a slurry material to hold the second sewer pipe in position. The slurry will harden in place to form an integral unit with the second pipe and the positioning walls or arms.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of the U.S. patent application Ser. No. 10/790,471, filed Mar. 1, 2004, now U.S. Pat. No. 7,021,338, which is a continuation-in-part of the U.S. patent application Ser. No. 10/247,430, filed Sep. 19, 2002, now U.S. Pat. No. 6,698,442, which application claims the benefit of U.S. provisional patent application Ser. No. 60/401,714, filed Aug. 7, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to an apparatus and a method for separating sanitary effluent from storm water and/or infiltrated water in a municipal sewer system. 
     Municipal sewer systems include a web of pipes that convey wastewater from homes, businesses and industries and storm water from drains to treatment plants. The smallest pipes, typically twelve inches in diameter or less, are know as “collectors” that are connected to service lines running to the sanitary plumbing of buildings. The collectors are connected to “trunk lines”, typically larger than twelve inches in diameter, and carrying one to ten million gallons per day. The trunk lines connect to “interceptors” that carry the wastewater to a treatment plant. The interceptors are of large diameter, often more than ten feet. 
     The wastewater plumbing system in a typical house, office building or manufacturing facility combines toilet effluent with other wastewater, such as from sink and bath drains, to be carried by a single service line to the collector line at the street. Hereinafter, such combined wastewater will be termed “sanitary effluent”. Some municipal sewer systems combine and carry in the same pipes the sanitary effluent from buildings, storm water from outside drains and any ground water leaking into the system (infiltrated water). Other municipal systems combine and carry in the same lines sanitary effluent from buildings, infiltrated water, and water from downspouts and/or footing drains, while having a separate storm drain system, but which in any case the two systems are interconnected downstream. When the treatment plant and the associated web of pipes are built, the system is sized to process a predetermined number of gallons per unit of time, the maximum flow capacity, including a certain rainfall amount. As additional buildings are connected to the system, less of the predetermined flow capacity is available for storm water. Thus, the system becomes susceptible to rainfall amounts less than the planned certain rainfall amount causing numerous overflows into streams and lakes and backups into buildings through the service lines. Overflows also can occur in systems where the storm water is carried in a separate set of pipes. Such overflows and backups cause serious environmental and health problems. 
     Also, some sewer systems were designed with less capacity than is required to carry typical rainfall amounts thereby always overflowing during normal rainfalls. Typically, such systems were installed before there was much concern for the effect of the overflow on the environment. 
     However, no matter what the configuration of an existing sewer system, it either now has or will in the near future have flow capacity problems causing overflows, backups and leaks. Consequently, the local governments responsible for maintaining these sewer systems face enormous expenses to repair or replace the existing pipes and/or add capacity. 
     SUMMARY OF THE INVENTION 
     The present invention concerns an apparatus and method for improving the operation of sewer systems while reducing the cost of increasing system capacity. The apparatus according to the present invention includes a first set of sewer lines connected to at least one storm water drain, and/or source of infiltrated water, and/or source of sanitary effluent, and a second set of sewer lines of smaller diameter than said sewer lines of said first set connected to sources of sanitary effluent, the first and second sets of lines being separately connected to a sewerage treatment plant. The second set of sewer lines has at least a portion thereof that extends inside the first set of sewer lines and the first set of sewer lines can be an existing sanitary sewer system. The apparatus can include at least one sanitary effluent process device connected to the second set of sewer lines such as a pumping station, a grinder pump or a vacuum system to assist the flow of the sanitary effluent through the second set of sewer lines. The apparatus can provide the same flow volume in a smaller diameter pipe that is under pressure. 
     The method according to the present invention includes the steps of: a. providing a first set of sewer lines connected between at least one source of storm water, and/or source of infiltrated water, and/or source of sanitary effluent, and at least one sewerage treatment plant; b. providing a second set of sewer lines connected between a source of sanitary effluent and the sewerage treatment plant; and c. installing at least a portion of said second set of sewer lines in said first set of sewer lines. Step b. can include installing a sanitary effluent collector line spaced from a collector line of the first set of sewer lines and connecting a service line from the source of sanitary effluent to the sanitary effluent collector line. Step c. can include running the sanitary effluent collector line to a manhole associated with the collector line of the first set of sewer lines and connecting the sanitary effluent collector line to a portion of the second set of sewer lines installed in the first set of sewer lines. Step c. can be performed by in situ forming of pipe included in the second set of sewer lines. 
     A sewer system according to the present invention reduces the size of the pipe required to carry sanitary effluent and/or increases the capacity of the sewerage treatment plant to treat sanitary effluent. Since the storm water and infiltrated water are separated from the sanitary effluent, they may require little or no treatment freeing plant capacity to treat the sanitary effluent. In some cases, treatment plant expansion can be delayed or eliminated. 
     A combined sewer pipe apparatus according to the present invention, for conveying sanitary effluent and storm water from sources to a treatment plant, includes: a larger diameter first sewer pipe adapted to carry storm water and having an interior surface; a smaller diameter second sewer pipe adapted to carry sanitary effluent and extending through the first sewer pipe adjacent the interior surface; and a fastener means attaching the second sewer pipe to the interior surface of the first sewer pipe, the fastener means including a plurality of fasteners spaced apart along a length of the second sewer pipe and engaging an exterior surface of the second sewer pipe and an adhesive material attaching the fasteners to the interior surface of the first sewer pipe. The apparatus can further include a liner extending through the first sewer pipe, the second sewer pipe being positioned between the interior surface of the first sewer pipe and an exterior surface of the liner. The second sewer pipe can be formed of an HDPE material and the fasteners formed of a suitable plastic that can be adhesively secured to the first sewer pipe. 
     In alternate embodiments of the present invention, the fasteners are not required. An alternate embodiment combined sewer pipe apparatus for conveying sanitary effluent and storm water from sources to a treatment plant includes: a larger diameter first sewer pipe adapted to carry storm water and having an interior surface surrounding an interior space; a smaller diameter second sewer pipe adapted to carry sanitary effluent and extending through the first sewer pipe at a predetermined position in the interior space; a longitudinally extending positioning means in contact with an exterior surface of the second sewer pipe and the interior surface of the first sewer pipe whereby the positioning means, the second sewer pipe and the interior surface of the first sewer pipe form a pair of longitudinally extending positioning spaces separated from a remainder of the interior space; and a positioning mixture contained in the positioning spaces in contact with the exterior surface of the second sewer pipe to maintain the second sewer pipe in the predetermined position. 
     The positioning means can be a bladder filled with water and the positioning mixture can be a curable adhesive. The bladder is inflated to maintain the second sewer pipe against the interior surface of the first sewer pipe, the curable adhesive material is injected into contact with adjacent portions of the interior surface of the first sewer pipe and the exterior surface of the second sewer pipe, and the bladder is deflated and removed the bladder from the first sewer pipe after the adhesive material is cured enough to maintain the second sewer pipe in the predetermined position. 
     Alternatively, the second sewer pipe and the positioning means can be formed as an integral unit from a suitable material such as an HDPE material. The positioning mixture can be a slurry mixture that hardens in place. The positioning means can include a semicircular first wall attached to the second sewer pipe and conforming to the first sewer pipe interior surface. The positioning means can include a straight second wall extending between opposed edges of the first wall and attached to the second sewer pipe whereby the first wall, the second wall and the second sewer pipe form the positioning spaces. Alternatively, the positioning means can include a curved second wall extending between opposed edges of the first wall and attached to the second sewer pipe whereby the first wall, the second wall and the second sewer pipe form the positioning spaces. Alternatively, the positioning means can include a pair of arms extending in opposite directions from the second sewer pipe into contact with the interior surface of the first sewer pipe whereby the arms, the second sewer pipe and a portion of the interior surface of the first sewer pipe form the positioning spaces, and another pair of arms extending in opposite directions from the second sewer pipe in the positioning spaces. 
     A method of installing the combined sewer pipe apparatus according to the present invention includes the steps of: a. inserting into the first sewer pipe a smaller diameter second sewer pipe adapted to carry sanitary effluent and extending the second sewer pipe through the first sewer pipe at a predetermined position adjacent an interior surface of the first sewer pipe; b. providing a positioning means in contact with the interior surface of the first sewer pipe to form at least one longitudinally extending positioning space; and c. inserting a positioning material into the at least one positioning space in contact with an exterior surface of the second sewer pipe to maintain the second sewer pipe in the predetermined position. The positioning means can be formed integral with the second sewer pipe and the method then includes the step of injecting a slurry material as the positioning material whereby the slurry material has a specific gravity high enough to maintain the second sewer pipe in the predetermined position. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The above, as well as other, advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a schematic block diagram of a typical prior art sewer system; 
         FIG. 2  is a schematic block diagram of a sewer system in accordance with a first embodiment of the present invention; 
         FIG. 3  is a cross-sectional view through one of the collector lines of the system shown in  FIG. 2  with a nested sanitary collector line; 
         FIG. 4  is a schematic block diagram of a portion of the system shown in  FIG. 2  with process devices added; 
         FIG. 5  is a schematic block diagram of a sewer system in accordance with a second embodiment of the present invention; 
         FIG. 6  is an end view of a separated sewer pipe in accordance with the present invention; 
         FIG. 7  is an end view of an alternate embodiment separated sewer pipe in accordance with the present invention; 
         FIG. 7   a  is an end view of a variation of the separated sewer pipes shown in  FIGS. 6 and 7 ; 
         FIG. 8  is an end view of a second alternate embodiment separated sewer pipe in accordance with the present invention; 
         FIG. 9  is an end view of a third alternate embodiment separated sewer pipe in accordance with the present invention; 
         FIG. 10  is an end view of a fourth alternate embodiment separated sewer pipe in accordance with the present invention; and 
         FIG. 11  is an end view of a fifth alternate embodiment separated sewer pipe in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     There is shown in  FIG. 1  a typical sanitary sewer system  10  of known construction. Each one of a plurality of building sewer systems  11   a  through  11   c  collects wastewater discharged from sources in the associated building and combines that wastewater as a discharge to a sanitary sewer system. Each one of the building sewer systems  11   a  through  11   c  is connected by an associated one of a plurality of service lines  12   a  through  12   c  respectively to a collector line  13   a . Thus, sanitary effluent from such sources as toilets, and other wastewater such as from sink drains, tub and shower drains, clothes washer drains and floor drains are combined to flow into the collector line  13   a . Also, one or more storm drains, such as a storm drain  14 , can be connected to the collector line  13   a . The collector line  13   a  and collector lines  13   b  through  13   c  feeding from other areas are connected to a trunk line  15   a . In a similar manner, other service lines, storm drains and collector lines are connected to trunk lines  15   b  and  15   c . The trunk lines  15   a  through  15   c  are connected to an interceptor line  16   a  leading to a sewerage treatment plant  17  that is connected to other interceptor lines  16   b  and  16   c . Thus, wastewater, including sanitary effluent and storm water combined, flows through the collector lines, the trunk lines and the interceptor lines in a typical sanitary sewer system  10 . 
     While the prior art sewer system  10  is adequate for most conditions, a heavy rain entering the storm drain  14  can cause a problem by exceeding the capacity of the system to carry all of the entering water to the treatment plant  17 . Overflow relief devices  18  are provided to release the wastewater from the system into drainage ditches, ponds, rivers and lakes. Although the overflow devices  18  are shown at the junction of the collector lines with the trunk line and the junction of the trunk lines with the interceptor line, the overflow devices can be connected at any suitable points in the sewerage system. A sewerage system operating near capacity may have frequent overflow problems causing contamination of swimming and boating areas with fecal matter and other wastes. Also, exceeding the system capacity causes backup through the service lines  12   a  through  12   c  typically flooding buildings with the combined sanitary effluent and storm water. The present invention seeks to solve the overflow and backup problem and increase the water treatment capacity of the sewer system by separating the sanitary effluent from the storm water as both flow through the system. 
     There is shown in  FIG. 2  a first embodiment sanitary sewer system  20  according to the present invention wherein the sanitary effluent is completely separated from the remainder of the building wastewater. As also shown in  FIG. 1 , each of the building sewer systems  11   a  through  11   c  is connected by an associated one of the plurality of service lines  12   a  through  12   c  respectively to the collector line  13   a . Thus, wastewater from such sources as sink drains, tub and shower drains, clothes washer drains and floor drains is combined to flow into the collector line  13   a . However, the sanitary effluent from the toilets is connected to each of a plurality of sanitary effluent service lines  22   a  through  22   c  to carry the sanitary effluent to a sanitary effluent collector line  23   a  separate from the original collector line  13   a . While new construction can be built with the required separated plumbing, existing building would require conversion. As an alternative, the new service lines  22   a  through  22   c  could be connected to and the old service lines  12   a  through  12   c  disconnected from the existing plumbing. Sanitary effluent collector lines  23   a  through  23   c  are connected to a sanitary effluent trunk line  25   a  that is connected to a sanitary effluent interceptor line  26   a  with other sanitary effluent trunk lines  25   b  and  25   c . The sanitary effluent lines  23   a  through  23   c ,  25   a  through  25   c , and  26   a  are interconnected at connectors  28  that do not require overflow protection. Thus, the sanitary effluent is separated from the other wastewater and will not overflow or back up into the buildings when storm water overloads the system  20 . 
     Although the sanitary effluent lines  22   a  through  22   c ,  23   a  through  23   c ,  25   a  through  25   c  and  26   a  could be run parallel to the other lines  12   a  through  12   c ,  13   a  through  13   c ,  15   a  through  15   c  and  16   a , it is preferred that sanitary effluent lines run inside the other lines where possible to avoid digging separate trenches. Since existing sewer lines typically run through developed land, the installation of parallel lines can be extremely costly and very disruptive to homes and businesses. Thus, the existing sewer system  10  can be retrofitted with the new sanitary effluent lines. The sanitary effluent pipes will be of a smaller diameter than the corresponding pipes of the existing system  10  since the volume of sanitary effluent wastewater to be carried is less and the addition of pressure increases the flow rate.  FIG. 3  shows the smaller diameter sanitary effluent connector line  23   a  extending inside the larger diameter collector line  13   a  that now only conveys storm water. Although the line  23   a  is shown spaced above a bottom of the outer line  13   a , such representation is only for the purpose of clearly illustrating two separate lines and the sanitary effluent connector line  23   a  typically would rest on the bottom of the connector line  13   a . Similarly, the sanitary effluent trunk line  25   a  would run inside the trunk line  15   a  and the sanitary effluent interceptor line  26   a  would run inside the interceptor line  16   a.    
     In order to properly convey the sanitary effluent wastewater to the treatment plant  17 , one or more process devices may be required. For example, as shown in  FIG. 4 , a first process device  29   a  is connected between the collector line  23   a  and the trunk line  25   a . A second process device  29   b  is connected between the trunk line  25   a  and the interceptor line  26   a . The process devices  29   a  and  29   b  can be pumping stations, grinder pumps, vacuum systems, or any other type of device used to assist the flow through the lines of the sewer system  20 . The process devices can be inserted at any point in the sewer system  20  and different types can be used together as required. 
     Since the flow through the sanitary effluent lines  23   a ,  25   a , and  26   a  is assisted by pressure or vacuum, the flow rate is greater than in a prior art gravity system for the same diameter pipe. Thus, the cross-sectional area required to flow the same volume is reduced leaving more room in the other wastewater lines  13   a  through  13   c ,  15   a  through  15   c  and  16   a  thereby increasing the capacity to carry storm water. When there is an overflow condition, the water escaping from the overflow devices  18  is not contaminated with effluent. Also, the wastewater flowing in the lines  12   a  through  12   c ,  13   a  through  13   c ,  15   a  through  15   c  and  16   a  either does not have to be treated at the plant  17  or may require only a primary treatment. Thus, another advantage of the present invention is the freeing of significant capacity of existing plants to treat additional wastewater from the sanitary effluent lines and a reduction in the size of new treatment plants. 
     In some situations, it is desirable not to provide the sanitary effluent service lines  22   a  through  22   c  shown in  FIG. 2 , such as when retrofitting an existing system. There is shown in  FIG. 5 , a second embodiment sanitary sewer system  30  wherein the service lines  12   a  through  12   c  are connected to the sanitary effluent connector line  22   a  that runs parallel to the collector line  13   a . Both of the collector lines  13   a  and  22   a  run into a manhole  31  wherein the line  22   a  can be inserted into the line  13   a . From the manhole  31 , the sanitary effluent lines run inside the corresponding existing sewer lines as in the system shown in  FIG. 2 . 
     The sewer system according to the present invention can be installed as a complete new system or during the repair of an existing system wherein the existing collector, trunk and interceptor lines are used as a first set of sewer lines that are connected to a source of storm water. The sanitary effluent lines according to the present invention are a second set of smaller diameter sewer lines that can be made of any suitable material such as plastic or composition materials and these lines can be placed in sections that are connected together or formed in situ during installation. A sewer system according to the present invention will prevent, or at least reduce overflows, and will eliminate backups into buildings. A sewer system according to the present invention provides a relatively inexpensive way to solve pollution problems and to modernize and expand existing sewer systems. 
     There is shown in  FIG. 6  a separated sewer pipe  40  according to the present invention for use in the above-described sewer systems. An existing larger diameter combined sewer pipe  41 , typically formed of a concrete or steel material, has an interior through which a new smaller diameter sanitary sewer pipe  42  has been inserted. The new pipe  42  can be formed of, for example, a suitable HDPE (high density polyethylene) plastic material. It is desirable to fix the new pipe  42  to an interior surface  41   a  of the existing outer pipe  41 . A fastener  43  is utilized for this purpose and preferably is formed from a molded plastic material or other material suitable for adhesion to the outer pipe  41 . The fastener  43  can be of continuous form, extending the length of the pipe  42 , or provided as a plurality of fastener straps spaced apart along the longitudinal axis of the pipe  42  at suitable intervals as shown in  FIG. 3  being used with the collector line  23   a . The fastener  43  can be free or can be attached to the outer surface of the pipe  42  by any suitable means such as adhesive or ultrasonic welding. 
     The fastener  43  has an arcuate central portion  44  that is curved to engage a part of an outer surface of the pipe  42 . Extending from either end of the central portion  44  is an end portion  45  that is shaped to engage a part of the inner surface  41   a  of the pipe  41 . The end portions  45  are attached to the pipe  41  with a suitable adhesive material  46  that adheres to both concrete and plastic and is moisture resistant. The adhesive  46  also can fill spaces  47  surrounded by the facing surfaces of the pipe  41 , the pipe  42  and the fastener  43 . One adhesive that can be used is a 3M Scotch-Grip Industrial Adhesive  4799  available from 3M Adhesives Division in St. Paul, Minn. In the continuous form, the fastener  43  requires slots or apertures (not shown) formed therein for introducing the adhesive  46  between the end portions  45  and the surface  41   a  and into the spaces  47 . 
     Although the pipe  42  is shown in  FIG. 6  as being mounted at the bottom of the interior of the pipe  41 , it can be mounted at any desired point along the circumference of the inner wall  41   a . For example, in  FIG. 7 , the pipe  42  is shown mounted at the top of the interior of the outer pipe  41 . This mounting can be the same as is shown in  FIG. 6  utilizing the hanger  43  and the adhesive material  46 . However,  FIG. 7  shows a separated sewer pipe  50 , according to an alternate embodiment of the present invention for use in the above-described sewer systems. When the existing combined sewer pipe  41  has a rough interior surface  41   a  and/or is cracked and leaking, it may be desirable to provide a longitudinally extending lining  51 . The lining  51  can be inserted into the interior of the existing sewer pipe  41  or can be formed in situ after the new pipe  42  is installed. The lining  51  holds the pipe  42  in place and the hangers  43  and the adhesive  46  are not required. 
     Although the separated sewer pipes  40  and  50  have been discussed in terms of utilizing the existing combined sewer pipe  41 , a new storm sewer pipe can be provided where the old pipe must be replaced or in new construction installations. 
     As shown in  FIG. 3 , the fasteners  43  can be used with a grout material or an adhesive material  48  applied along the entire length of the sanitary sewer pipe  23   a  ( 42 ). Furthermore, if the grout/adhesive material alone  48  is a sufficient fastening means, the fasteners  43  can be eliminated. For example, there is shown in  FIG. 7   a  a separated sewer pipe  50 ′, according to a variation of the sewer pipes shown in  FIGS. 6 and 7 . The sewer pipe  42  is held in place by a positioning material  46 ′ such as a suitable water resistant adhesive. In order to maintain the pipe  42  in place against the interior wall  41   a  of the existing sewer pipe  41 , a longitudinally extending inflatable bladder  51 ′ can be inserted in the pipe  41  and inflated with, for example, water. The bladder  51 ′, the pipe  42  and a portion of the interior surface  41   a  form two longitudinally extending positioning spaces  55  into which the uncured adhesive  46 ′ is inserted. The bladder  51 ′ holds the pipe  42  in place in a predetermined position while the adhesive  46 ′ cures or dries and then the bladder is deflated and removed. The cured adhesive  46 ′ holds the pipe  42  in place in the predetermined position after the bladder  51 ′ is removed. 
     There is shown in  FIG. 8  a separated sewer pipe  60  according to a second alternate embodiment of the present invention for use in the above-described sewer systems. The larger diameter pipe  41  has an interior through which the smaller diameter sanitary sewer pipe  42  has been inserted. The fastener  43  is preferably extruded from a plastic material and can be of continuous form, extending the length of the pipe  42 , or provided as a plurality of fastener straps spaced apart along the longitudinal axis of the pipe  42  at suitable intervals as shown in  FIG. 3  being used with the collector line  23   a . The fastener  43  can be free or can be attached to the outer surface of the pipe  42  by any suitable means such as adhesive or ultrasonic welding. 
     The fastener  43  has an arcuate central portion  44  that is curved to engage a part of an outer surface of the pipe  42 . Extending from either end of the central portion  44  is an end portion  45  that is shaped to engage a part of the inner surface  41   a  of the pipe  41 . The end portions  45  are attached to the pipe  41  with a suitable adhesive material  46  that adheres to both concrete and plastic and is moisture resistant. In the continuous form, the fastener  43  requires slots or apertures (not shown) formed therein for introducing the adhesive  46  between the end portions  45  and the surface  41   a.    
     Although the pipe  42  is shown in  FIG. 8  as being mounted at the top of the interior of the pipe  41 , it can be mounted at any desired point along the circumference of the inner wall  41   a . For example, in  FIG. 6 , the pipe  42  is shown mounted at the bottom of the interior of the outer pipe  41 . When the existing combined sewer pipe  41  has a rough interior surface  41   a  and/or is cracked and leaking, it may be desirable to provide the lining  51 . The lining  51  can be inserted into the interior of the existing sewer pipe  41  or can be formed in situ after the new pipe  42  is installed. The wall of the lining  51  extends inwardly around the pipe  42  and the fastener  43 . 
     There is shown in  FIG. 9  a separated sewer pipe  70  according to third alternate embodiment of the present invention for use in the above-described sewer systems. The larger diameter pipe  41  has an interior through which a pipe and positioning assembly  71  has been inserted. The assembly  71  is preferably extruded from a plastic material in continuous form and includes a smaller diameter sanitary sewer pipe  72 . The assembly  71  also has a first wall  73  that is curved to conform to a portion of the interior wall  41   a  of the pipe  41  and is integral with the pipe  72  at a bottom portion thereof. The assembly  71  has a second wall  74  that extends horizontally and is integral with the pipe  72  at a top portion thereof. The adjacent edges of the walls  73  and  74  are joined such that the pipe  72 , the first wall  73  and the second wall  74  form two longitudinally extending positioning spaces  75 . The spaces  75  are filled with a positioning material  76 , such as a high specific gravity slurry mixture, that will harden in place to form an integral unit with the assembly  71 . The weight of the slurry mixture  76  will maintain the pipe and positioning assembly  71  in place in a predetermined position at the bottom of the larger diameter pipe  41  without the requirement for fasteners and/or adhesive. 
     There is shown in  FIG. 10  a separated sewer pipe  80  according to fourth alternate embodiment of the present invention for use in the above-described sewer systems. The larger diameter pipe  41  has an interior through which a pipe and positioning assembly  81  has been inserted. The assembly  81  is preferably extruded from a plastic material in continuous form and includes a smaller diameter sanitary sewer pipe  82 . The assembly  81  also has a first wall  83  that is curved to conform to a portion of the interior wall  41   a  of the pipe  41  and is integral with the pipe  82  at a bottom portion thereof. The assembly  81  has a second wall  84  that extends generally horizontally and is integral with the pipe  82  at a top portion thereof. The adjacent edges of the walls  83  and  84  are joined such that the pipe  82 , the first wall  83  and the second wall  84  form two longitudinally extending positioning spaces  85 . The spaces  85  are filled with a positioning material, such as a high specific gravity slurry mixture, that will harden in place to form an integral unit with the assembly  81 . The weight of the slurry mixture  86  will maintain the pipe and positioning assembly  81  in place in a predetermined position at the bottom of the larger diameter pipe  41  without the requirement for fasteners and/or adhesive. In contrast to the wall  74  shown in  FIG. 9 , the wall  84  follows the curve of the pipe  82  and then extends toward the interior wall  41   a  curving downwardly and then upwardly before joining the ends of the first wall  83 . Consequently, the spaces  85  are smaller in cross section than the spaces  75  proving a larger area of the pipe  41  for carrying storm water. 
     There is shown in  FIG. 11  a separated sewer pipe  90  according to fifth alternate embodiment of the present invention for use in the above-described sewer systems. The larger diameter pipe  41  has an interior through which a pipe and positioning assembly  91  has been inserted. The assembly  91  is preferably extruded from a plastic material in continuous form and includes a smaller diameter sanitary sewer pipe  92 . The assembly  91  also has a pair of first arms  93  that are integral with the pipe  92 . The arms  93  are curved and extend toward but do not contact the interior wall  41   a  of the pipe  41 . The assembly  91  has a pair of second arms  94  positioned above the first arms  93  that are curved and extend to edges in contact with the interior wall  41   a . The wall  41   a , the pipe  92  and the second arms  94  form two longitudinally extending positioning spaces  95 . The spaces  95  are filled with a positioning material, such as a high specific gravity slurry mixture, that will harden in place to form an integral unit with the assembly  91 . The weight of the slurry mixture  96  will maintain the pipe and positioning assembly  91  in place in a predetermined position at the bottom of the larger diameter pipe  41  without the requirement for fasteners and/or adhesive. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.