You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
       [0001]     The field of the invention is connections between plumbing fixtures and drainage piping and in particularly the invention relates to sealing water closets to an associated drain pipe.  
         [0002]     Water closets are commonly connected to a three inch or a four inch PVC plastic drain pipe using a standardized PVC plastic closet flange. The downwardly extending annulus or hub of the plastic closet flange is dimensioned to accept a three inch plastic drain pipe in its interior and a four inch plastic drain pipe on its exterior. In both instances the plastic drain pipe is secured to the closet flange hub by a commercially available solvent cement.  
         [0003]     It has long been recognized that the connection between the water closet and the drain pipe is the most troublesome connection in the plumbing system. A leaking connection will allow sewer gas to enter the building and if stoppage occurs in the drain pipe, sewage may be discharged into the cavity beneath the water closet with attendant breeding of germs. It is customary to use putty or a wax ring to seal the water closet to the closet flange or the drain pipe; however, such sealing arrangements are often ineffective. There have been many attempts to improve the sealing between the water closet and the drain pipe as evidenced by a U.S. Pat. No. 2,976,543 issued Mar. 28, 1961 to H. J. Turner et al. for a Gasket Ferrule, a U.S. Pat. No. 5,185,890 issued Feb. 16, 1993 to G. W. Dismore et al. for a Toilet Bowl Sealing Assembly, a U.S. Pat. No. 5,291,619 issued Mar. 8, 1994 to C. R. Adoijan for a Water Closet Sealing Adapter, a U.S. Pat. No. 5,937,450 issued Aug. 17, 1999 to B. Jones for a Method and Device for Attaching Fittings to Receptacle and a U.S. Pat. No. 6,070,910 issued Jun. 6, 2000 to B. E. Hodges for a Push-In Closet Flange. These and other proposed solutions to the water closet sealing problem have not been found satisfactory for a number of reasons. Some require too many parts, some are too costly and some do not accommodate both three and four inch sewer pipe.  
       SUMMARY OF THE INVENTION  
       [0004]     An inexpensive one piece seal adapter is provided for sealing a water closet connected by a closet flange to either a three inch drain pipe or a four inch drain pipe. The seal adapter is made of an elastic plastic and includes a tubular portion with a pair of axially spaced annular flanges extending radially outward from the tubular portion a sufficient distance to make sealing contact with the interior of either a three inch sewer pipe or with the interior of the tubular part of the closet flange when a four inch sewer pipe is connected thereto. The seal adapter includes a radially outward extending annulus at the upper end of the tubular portion and preferably has a washer shaped seal adhesively secured at its underside to the upper surface of the annulus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     The invention is illustrated in the accompanying drawings, in which:  
         [0006]      FIG. 1  is a section showing the seal adapter between a water closet and a three inch sewer pipe;  
         [0007]      FIG. 2  is a section showing the seal adapter between a water closet and four inch sewer pipe;  
         [0008]      FIG. 3  is a section of the seal adapter, and  
         [0009]      FIG. 4  is a section of the seal adapter installed between a water closet and a four inch sewer pipe including an additional sealing washer between the adapter and the top of the closet flange.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     As illustrated in  FIG. 1 , a water closet  11  is secured to a floor  12  by a somewhat standard closet flange  13  having a collar  14  connected to the base  15  of the water closet  11  by bolts and nuts, such as the bolt  16  and the nut  17  shown in  FIG. 4 . The collar  14  is secured to the floor  12  by screws  18 . The closet flange  13  includes a tubular part  19  which extends downwardly through an opening  21  in the floor  12 . The interior diameter of the tubular part  19  is approximately the same as the exterior diameter of a three inch sewer pipe  22  and, as shown in  FIGS. 2 and 4 , the exterior diameter of the tubular part  19  is substantially the same as the four inch interior diameter of a four inch sewer pipe  23 . The closet flange  13  and the sewer pipes  22 ,  23  are typically made of PCV plastic and are interconnected, as shown in the drawings, by solvent cement. The water closet  11  has a discharge opening  26  in a downwardly extending annular protuberance  27  which is in general alignment with the floor opening  21  and with the tubular part  19  of the closet flange  13 . A downwardly facing flat surface  28  surrounds the protuberance  27  in the cavity on the underside of the base  15  of the water closet  11 .  
         [0011]     A one piece elastic plastic seal adapter  31  forms a sealing connection against gas and sewage leakage between the underside surface  28  of the water closet  11  and the closet flange  13  when either one of the sewer pipes  22  or  23  is attached to the closet flange  13 . The seal adapter  31  includes a flat horizontal annulus  32  which, as shown in  FIG. 3 , has parallel upper and lower surfaces  33 ,  34  in confronting or sealing relation to the underside surface  28  of the water closet  11  and the upward facing surface  36  of the collar  14 , respectively. As illustrated in  FIGS. 1 and 2  the annulus  32  of the seal adapter  31  includes a foam plastic washer shaped seal  37  whose underside is adhesively secured to the annulus  32  of the adapter  31  and whose top side is adhesively secured to the downward facing surface  28  of the water closet  11 .  FIG. 4  shows a second embodiment of the invention in which a second foam plastic washer  41  is adhesively bonded to the underside of the annulus  32  of the seal adapter  31 . The second foam plastic washer  41  is used for non-standard water closets.  
         [0012]     The one piece adapter seal  31  includes a tubular portion  46  which extends downwardly from the interior diameter of the annulus  32  and has an outside diameter substantially smaller than the inside diameter of the tubular part  19  of the closet flange  13 . A pair of axially spaced elastic plastic annular flange seals  47 ,  48  are integrally formed with and extend radically outward from the tubular portion  46  a sufficient distance to form an effective seal with the inside diameter of the  3  inch sewer pipe  22 , as shown in  FIG. 1 , or with the inside diameter of the tubular part  19  of the closet flange  13 , as shown in  FIG. 2 , wherein a  4  inch sewer pipe  23  is connected to the tubular part  19 . As shown in  FIG. 3 , in which an uninstalled seal adapter  31  is illustrated, the thickness of the flange seals  47 ,  48  tapers radially from the tubular portion  46 . A thin removable plastic sheet  51  placed in protective cover on the top of the seal  37  is removed prior to installation of the seal adapter  31 .  
         [0013]     The seal adapter  31  shown in  FIG. 3  is an effective one-piece seal for a water closet connection to either a  3  inch or  4  inch sewer pipe. The plumber need only be concerned about being supplied with a single component for sealing water closets to 3 or 4 inch sewer pipes, which covers most residential buildings and a large portion of commercial buildings.

Summary:
A single piece adapter is provided for use in sealing a water closet to sewer pipes of different diameters.