Exhibit 5.01


                                  April 1, 1998


United States Filter Corporation
40-004 Cook Street
Palm Desert, California 92211

Ladies and Gentlemen:

   
      We have acted as counsel to United States Filter  Corporation,  a Delaware
corporation   (the  "Company")  in  connection  with  Amendment  No.  1  to  the
Registration Statement on Form S-3 (the "Amended Registration Statement"), filed
by the  Company on April 1, 1998 with the  Securities  and  Exchange  Commission
pursuant  to the  Securities  Act of 1933,  as amended,  with  respect to (i) an
aggregate of  5,803,803  shares (the "Merger  Shares") of the  Company's  Common
Stock,  par  value  $.01 per share  ("Common  Stock"),  that were  issued by the
Company pursuant to the Merger Agreement dated as of December 31, 1997 among the
Company, The Kinetics Group, Inc., U.S. Filter/KG  Acquisition Corp., The Bianco
Family  1991 Trust,  Dated  February  1, 1991,  David J.  Shimmon and BT Capital
Partners,  Inc. (the "Merger  Agreement") and (ii) an aggregate of 11,647 shares
of the Common Stock that may be issued upon exercise of options (the  "Options")
which were  converted in accordance  with the Merger  Agreement  from options to
purchase shares of Kinetics Common Stock (the "Option Shares").
    
   
      We are familiar with the Amended Registration  Statement and have reviewed
the Company's  Certificate  of  Incorporation  and By-laws,  each as amended and
restated.  We have also  examined  such other  public and  corporate  documents,
certificates,  instruments and corporate records,  and such questions of law, as
we have deemed  necessary  for purposes of  expressing an opinion on the matters
hereinafter set forth. In all  examinations of documents,  instruments and other
papers,  we have  assumed the  genuineness  of all  signatures  on original  and
certified  documents and the  conformity to original and certified  documents of
all copies submitted to us as conformed, photostatic or other copies.
    

      On the  basis of the  foregoing,  we are of the  opinion  that the  Merger
Shares are, and the Option Shares,  when issued in accordance  with the terms of
the Options, will be, validly issued, fully paid and non-assessable.

   
      We consent to the filing of this  opinion as Exhibit  5.01 to the  Amended
Registration  Statement and to the use of our name in the  Prospectus  forming a
part thereof under the caption "Legal Matters."
    

                                    Yours truly,



                                     /s/ Kirkpatrick & Lockhart LLP