EXHIBIT 21 Subsidiaries of the Registrant Set forth below is a listing, by name and jurisdiction of incorporation, of each corporation that is, as of the date of this report, a subsidiary of the Registrant. Unless otherwise indicated, each such corporation is a 100% owned subsidiary of the Registrant. 1) Carolina Pump & Supply Corporation, a Rhode Island corporation. 2) Century Air Supply, Inc., a Delaware corporation. 3) Century GP Management, LLC, a Delaware limited liability company. 4) Century LP Investments, LLC, a Delaware limited liability company. 5) Century Maintenance, L.P., a Delaware limited partnership. 6) Century Maintenance (Houston), L.P., a Delaware limited partnership. 7) Century Maintenance Management, LLC, a Delaware limited liability company. 8) Century Maintenance Supply, Inc., a Delaware corporation. 9) Century Maintenance Supply - S. Cal., Inc., a Delaware corporation. 10) Century Services, L.P., a Delaware limited partnership. 11) Douglas Leonhardt & Associates, Inc., a North Carolina corporation. 12) Electric Laboratories and Sales Corporation, a Delaware corporation. 13) Gilleland Concrete Products, Inc., a Georgia corporation. 14) HHH, LLC, a Delaware limited liability company. 15) HSI Acquisition Corporation, an Ohio corporation. 16) HSI Funding, LLC, a Delaware limited liability company. 17) HSI Fusion Services, Inc., a Florida corporation. 18) HSI Holdings, Inc., a Delaware corporation. 19) HSI Indiana, LLC, an Indiana limited liability company. 20) HSI IP, Inc., a Delaware corporation. 21) HSI North Carolina LLC, a North Carolina limited liability company. 22) HSI Properties, LLC, a Delaware limited liability company. 23) Hughes Aviation, Inc., a Florida corporation. 24) Hughes Insurance Company, Ltd., a Bermuda company limited by shares. 25) Hughes Insurance Holdings, Inc. (fka Allstate Pool Supplies, Inc.), a Delaware corporation. 26) Hughes MRO, Inc. (fka Chad Supply, Inc.), a Florida corporation. 27) Hughes MRO, L.P., a Delaware limited partnership. 28) Hughes MRO 1, LLC, a Delaware limited liability company. 29) Hughes Supply CA, LLC, a California limited liability company. 30) Hughes Supply Foundation, Inc., a Florida not-for-profit corporation. 31) Hughes Supply IP, Inc., a Delaware corporation. 32) Hughes Supply Management Services, Inc., a Delaware corporation. 33) Hughes Supply Shared Services, Inc., a Delaware corporation. 34) Hughes Supply (VA), Inc. (fka Virginia Water & Waste Supply Company, Inc.), a Virginia corporation. 35) Hughes Water & Sewer Company, a West Virginia corporation. 36) Juno Industries, Inc., a Florida corporation. 37) Kamen Supply Company, Inc., a Kansas corporation. EXHIBIT 21 38) Kingston Pipe Industries, Inc., a Rhode Island corporation. 39) L & T of Delaware, Inc., a Delaware corporation. 40) Merex Corporation, a Texas corporation. 41) Merex De Mexico, Sociedad Anonima De Capital Variable, a Mexico corporation, 75% owned. 42) Merex Diesel Power, Sociedad Anonima De Capital Variable, a Mexico corporation, 75% owned. 43) Metals Inc., an Oklahoma corporation. 44) Metals, Inc. - Gulf Coast Division, an Oklahoma corporation. 45) Mills & Lupton Supply Company, a Tennessee corporation. 46) Moore Electric Supply, Inc., a North Carolina corporation. 47) Mountain Country Supply, Inc., an Arizona corporation. 48) National Powerx, Inc., a Pennsylvania corporation. 49) Olander & Brophy, Inc., a Pennsylvania corporation. 50) One Stop Supply, Inc., a Tennessee corporation. 51) Paine Supply of Jackson, Inc., a Mississippi corporation. 52) Panhandle Pipe & Supply Company, Inc., a West Virginia corporation. 53) Reaction Supply Corporation, a California corporation. 54) Scott-Parish Electrical Supply Company, a North Carolina corporation. 55) Shrader Holding Company, Inc., an Arkansas corporation. 56) Southwest Stainless, L.P., a Delaware limited partnership. 57) Stainless Tubular Products, Inc., an Oklahoma corporation. 58) SWS Acquisition LLC, a Delaware limited liability company. 59) SWS Funding LLC, a Delaware limited liability company. 60) U.S. Fusion Services, Inc., a Louisiana corporation. 61) USCO, Inc., a North Carolina corporation. 62) Utiliserve, Inc. (fka Temple Electric, Inc.), a Delaware corporation. 63) Utiliserve Holdings, Inc. (fka Utiliserve, Inc.), a Delaware corporation. 64) Waterworks Sales Company, a Colorado corporation. 65) Waterworks Holding Co., a Colorado corporation. 66) Warner Waterworks Sales Company of Wyoming, a Wyoming corporation. 67) WCC Merger Corporation, a Georgia corporation. 68) World-Wide Travel Network, Inc., a Florida corporation. 69) Z&L Acquisition Corporation, a Delaware corporation.