AMENDMENT NO. 1 TO RIGHTS AGREEMENT

EXHIBIT 4.1

AMENDMENT NO. 1

TO

RIGHTS AGREEMENT

AMENDMENT NO. 1, dated as of March 27, 2012 (this “Amendment”), to the Rights Agreement (the “Rights Agreement”), dated as of December 10, 2004, between PENTAIR, INC., a Minnesota corporation (the “Company”), and WELLS FARGO BANK, N.A., as the Rights Agent (the “Rights Agent”). Capitalized terms used in this Amendment but not otherwise defined herein shall have the meanings ascribed to such terms in the Rights Agreement.

WHEREAS, the Company and the Rights Agent entered into the Rights Agreement specifying the terms of the Rights;

WHEREAS, it has been proposed that the Company enter into an Merger Agreement to be dated the date hereof with Tyco International Ltd., a corporation limited by shares (Aktiengesellschaft) organized under the laws of Switzerland (“Parent”), Tyco Flow Control International Ltd., a corporation limited by shares (Aktiengesellschaft) organized under the laws of Switzerland and presently a wholly-owned subsidiary of Parent (“Spinco”), Panthro Acquisition Co., a Delaware corporation (“AcquisitionCo”) and a wholly-owned subsidiary of Spinco and Panthro Merger Sub, Inc., a Minnesota corporation (“Merger Sub”) and a wholly-owned subsidiary of AcquisitionCo;

WHEREAS, the Board of Directors of the Company desires to amend the Rights Agreement to render the Rights inapplicable to the Merger (as defined in the Merger Agreement) and the other transactions contemplated by the Merger Agreement;

WHEREAS, the Company deems this Amendment to be advisable and in the best interests of the holders of the Rights (including, prior to the Distribution Date, registered holders of the Common Shares) and at a duly convened meeting the Company’s Board of Directors has duly approved this Amendment;

WHEREAS, pursuant to Section 27 of the Rights Agreement, prior to such time as any Person becomes an Acquiring Person, and subject to certain exceptions set forth therein, the Company may, and the Rights Agent shall, if the Company so directs, supplement or amend any provision of the Rights Agreement without the approval of any holders of certificates representing Common Shares of the Company;

WHEREAS, no Person has become an Acquiring Person as of the date hereof;

WHEREAS, pursuant to Section 27 of the Rights Agreement, the Company has delivered to the Rights Agent a certificate signed by Angela Lageson, Senior Vice President, General Counsel & Secretary of the Company certifying that this Amendment complies with the terms of Section 27 of the Rights Agreement;

WHEREAS, the Company desires to amend the Rights Agreement in accordance with Section 27 of the Rights Agreement as set forth herein;

NOW, THEREFORE, in consideration of the premises and mutual agreements set forth in the Rights Agreement and this Amendment, the parties hereby agree as follows:

“AcquisitionCo” shall mean Panthro Acquisition Co., a Delaware corporation and a wholly-owned subsidiary of Spinco.

“Effective Time” shall have the meaning ascribed to such term in the Merger Agreement.

“Exempted Transaction” shall have the meaning set forth in the definition of Acquiring Person, as amended herein.

“Merger” shall have the meaning ascribed to such term in the Merger Agreement.

“Merger Agreement” shall mean the Merger Agreement by and among the Company, Parent, Spinco, AcquisitionCo, and Merger Sub dated as of March 27, 2012.

“Merger Sub” shall mean Panthro Merger Sub, Inc., a Minnesota corporation and a wholly-owned subsidiary of AcquisitionCo.

“Parent” shall mean Tyco International Ltd., a corporation limited by shares (Aktiengesellschaft) organized under the laws of Switzerland.

“Parent Group” shall have the meaning set forth in the definition of Acquiring Person, as amended herein.

“Spinco” shall mean Tyco Flow Control International Ltd., a corporation limited by shares (Aktiengesellschaft) organized under the laws of Switzerland and presently a wholly-owned subsidiary of Parent.

“Notwithstanding anything to the contrary set forth in this definition or in this Agreement, none of Parent, Spinco, AcquisitionCo, Merger Sub nor any Subsidiary (as such term is defined in the Merger Agreement) of Parent (collectively, the ‘Parent Group’) shall be, or shall be deemed to be, an Acquiring Person, either individually or collectively, solely by virtue of (A) the approval, execution, delivery or amendment of the Merger Agreement; (B) the public announcement of the Merger Agreement or the Merger; (C) the consummation of the Merger; or (D) the consummation of the other transactions contemplated by the Merger Agreement. Each event described in clauses (A), (B), (C) and (D) above is referred to herein as an ‘Exempted Transaction’.”

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“Notwithstanding anything to the contrary set forth in this definition or in this Agreement, the Parent Group, either individually or collectively, shall not be deemed to be a ‘Beneficial Owner’ of, to have ‘Beneficial Ownership’ of, or to ‘beneficially own’, any securities solely by virtue of or as a result of any Exempted Transaction.”

“(including in either case any such date which is after the date of this Agreement and prior to the Record Date; the earlier of such dates being herein referred to as the “Distribution Date”; provided, however, that if the tenth day or Business Day, as the case may be, after the pertinent date occurs before the Record Date, “Distribution Date” shall mean the Record Date; provided further that, notwithstanding anything to the contrary in this Section 3(a) or in this Agreement, a Distribution Date shall not be deemed to have occurred by virtue of or as a result of any Exempted Transaction or the public announcement thereof.)”

“Notwithstanding anything to the contrary set forth in this definition or in this Agreement, a Share Acquisition Date shall not be deemed to have occurred by virtue of or as a result of any Exempted Transaction or the public announcement thereof.”

“Nothing in this Agreement shall be construed to give any holder of Rights (including, prior to the Distribution Date, the Common Shares of the Company) or any person any legal or equitable right, remedy or claim under this Agreement by virtue of or in connection with any Exempted Transaction.”

“Notwithstanding anything to the contrary in this Section 11 or in this Agreement, a Section 11(a)(ii) Event shall not be deemed to have occurred by virtue of or as a result of any Exempted Transaction or the public announcement thereof.”

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“Notwithstanding anything to the contrary in this Section 13 or in this Agreement, a Section 13 Event shall not be deemed to have occurred by virtue of or as a result of any Exempted Transaction or the public announcement thereof.”

“(d) At the Final Expiration Date, (i) this Agreement shall be terminated and be void and of no further force or effect, (ii) none of the parties to this Agreement will have any rights, obligations or liabilities hereunder and (iii) the holders of the Rights (including, prior to the Distribution Date, registered holders of the Common Shares) shall not be entitled to any benefits, rights or other interests under this Agreement, including, without limitation, the right to purchase or otherwise acquire any securities of the Company.”

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly executed as of the day and year first above written.

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