EXHIBIT 21 LIST OF SUBSIDIARIES OF THE REGISTRANT Listed below are the subsidiares of Pentair, Inc.,all of which are either directly or indirectly 100% owned as of December 31, 1997, except as otherwise noted. Aplex Industries, Inc. United States APNO, S.A. de C.V. Mexico Biesemeyer Manufacturing Corporation United States Century Manufacturing Co. United States Delta International Machinery Corp. United States EuroPentair, GmbH Germany Fleck Controls, Inc. United States Fleck Europe, SAS France Flex Elektrowerkzeuge GmbH Germany Hoffman Enclosures Inc. United States Hoffman Engineering, S.A. de C.V. de SrL Mexico Hoffman Engineering Co Limited United Kingdom Hoffman-Schroff PTE Ltd. Singapore HS Systems. Inc. United States Lincoln Czech Republic Czech Republic Lincoln GmbH Germany Lincoln U.K. Ltd. United Kingdom McNeil (Ohio) Corporation United States ORSCO Acquisition Corp United States Pentair, Inc. United States Pentair FSC Corporation Virgin Islands (U.S.) Pentair Asia, PTE Ltd. Singapore Pentair Canada, Inc. Canada Pentair Financial Services Ireland Ireland Pentair Halifax, Inc. Canada Pentair Nova Scotia Co. Canada Pentair Pump Group United States Pentair U.K. Ltd. United Kingdom Penwald Insurance Company United States Porter-Cable Corporation United States Schroff Scandinavia AB Sweden Schroff S.r.L. Italy Schroff Inc. United States Schroff SAS France Schroff Co. Ltd. Taiwan Schroff K.K. Japan Schroff U.K. Ltd. United Kingdom Schroff, GmbH Germany SIATA S.p.A. Italy Telestack Company United States Transrack S.A. France