UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): May 20, 2014

Pentair Ltd.

(Exact name of Registrant as specified in its charter)

Freier Platz 10, 8200 Schaffhausen, Switzerland

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: 41-52-630-48-00

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Credit Agreement

In anticipation of the change of jurisdiction of organization of Pentair Ltd. (the “Company”) from Switzerland to Ireland pursuant to a merger (the “Merger”) of the Company with and into Pentair plc, an Irish public limited company and subsidiary of the Company (“Pentair-Ireland”), on May 20, 2014, Pentair-Ireland and Pentair Investments Switzerland GmbH, a Swiss company that will be a subsidiary of Pentair-Ireland and the parent of PFSA (as defined below) after the Merger (“SwissCo”), entered into an Assumption and Accession Agreement, dated as of May 20, 2014 (the “Accession Agreement”), to acknowledge that, effective upon the Merger, Pentair-Ireland will assume all of the Company’s obligations as a guarantor, and SwissCo will become an additional guarantor, under the Credit Agreement, dated as of September 21, 2012, among Pentair Finance S.A., a Luxembourg public limited liability company and subsidiary of the Company (“PFSA”), the Company, various affiliates of the Company and the financial institutions party thereto, as amended.

The foregoing is only a summary of the terms of the Accession Agreement and is qualified in its entirety by reference to the Accession Agreement, which is filed as Exhibit 4.1 to this Current Report on Form 8-K and is incorporated by reference herein.

Supplemental Indentures

In anticipation of the change of jurisdiction of organization of the Company from Switzerland to Ireland pursuant to the Merger, on May 20, 2014:

The foregoing is only a summary of the terms of the Fifth Supplemental Indenture and the Sixth Supplemental Indenture and is qualified in its entirety by reference to such Supplemental Indentures which are filed as Exhibits 4.2 and 4.3, respectively, to this Current Report on Form 8-K and are incorporated by reference herein.

The information included in Item 1.01 above is incorporated by reference herein.

Results of the Annual General Meeting

The Company held its 2014 annual general meeting of shareholders on May 20, 2014. There were 193,576,105 common shares issued and outstanding at the close of business on April 30, 2014 and entitled to vote at the annual general meeting. A total of 159,799,776 common shares (83%) were represented at the annual general meeting.

The items voted upon at the annual general meeting and the results of the vote on each proposal were as follows:

Proposal 1. — Re-Election of Nine Directors and Election of One Director

To re-elect nine directors and elect one director for one-year terms expiring at the 2015 annual general meeting of shareholders. Each nominee for director was re-elected or elected, as applicable, by a vote of the shareholders as follows:

Proposal 2. — Election of the Chairman of the Board of Directors

To elect Randall J. Hogan as Chairman of the board of directors to hold office until the 2015 annual general meeting of shareholders. Mr. Hogan was elected Chairman of the board of directors by a vote of the shareholders as follows:

Proposal 3. — Election of the Members of the Compensation Committee

To elect four incumbent directors as members of the compensation committee of the board of directors to hold office until the 2015 annual general meeting of shareholders. Each nominee to the compensation committee of the board of directors was elected by a vote of the shareholders as follows:

Proposal 4. — Election of the Independent Proxy

To elect Proxy Voting Services GmbH as the independent proxy at the 2015 annual general meeting of shareholders and also at any shareholder meeting that may be held prior to the 2015 annual general meeting of shareholders. Proxy Voting Services GmbH was elected as the independent proxy by a vote of the shareholders as follows:

Proposal 5. — Approval of the Annual Report and Financial Statements

To approve the 2013 annual report of the Company, the statutory financial statements of the Company for the year ended December 31, 2013 and the consolidated financial statements of the Company for the year ended December 31, 2013. The proposal was approved by a vote of the shareholders as follows:

Proposal 6. — Discharge of the Board of Directors and Executive Officers of the Company from Liability for the Year Ended December 31, 2013

To discharge the board of directors and executive officers of the Company from liability for their activities during the year ended December 31, 2013. The proposal was approved by a vote of the shareholders as follows:

Proposal 7(a). — Re-Election of Statutory Auditors

To re-elect Deloitte AG as the Company’s statutory auditors until the next annual general meeting. The proposal was approved by a vote of the shareholders as follows:

Proposal 7(b). — Ratification of Appointment of Independent Registered Public Accounting Firm

To ratify the appointment of Deloitte & Touche LLP as the Company’s independent registered public accounting firm for the year ending December 31, 2014. The proposal was approved by a vote of the shareholders as follows:

Proposal 7(c). — Election of Special Auditors

To elect PricewaterhouseCoopers AG as the Company’s special auditors until the next annual general meeting. The proposal was approved by a vote of the shareholders as follows:

Proposal 8(a). — Appropriation of Results for the Year Ended December 31, 2013

To approve the appropriation of results for the year ended December 31, 2013. The proposal was approved by a vote of the shareholders as follows:

Proposal 8(b). — Conversion and Appropriation of Reserves from Capital Contributions to Distribute an Ordinary Cash Dividend

To approve the conversion of reserves from capital contributions into free reserves in a total amount of $ 256 million and to appropriate them to distribute an ordinary cash dividend in the amount of $1.20 per share. Payment of the dividend will be made in four equal quarterly installments of $0.30 in each of the third and fourth quarters of 2014 and the first and second quarters of 2015 at such times and with such record dates as shall be determined by the board of directors of the Company. The proposal was approved by a vote of the shareholders as follows:

Proposal 9. — Advisory Vote to Approve the Compensation of the Named Executive Officers

To approve by advisory vote, the compensation of the Company’s named executive officers. The compensation of the Company’s named executive officers was approved by advisory vote by shareholders as follows:

Results of the Extraordinary General Meeting

The Company held an extraordinary general meeting of shareholders on May 20, 2014 to consider certain matters in connection with the Merger Agreement, dated as of December 10, 2013 (the “Merger Agreement”), between the Company and Pentair-Ireland, pursuant to which the Company effect the Merger, thereby changing the jurisdiction of organization of the Company from Switzerland to Ireland.

There were 193,576,105 common shares issued and outstanding at the close of business on April 30, 2014 and entitled to vote at the extraordinary general meeting. A total of 147,972,664 common shares (76%) were represented at the extraordinary general meeting.

The items voted upon at the extraordinary general meeting and the results of the vote on each proposal were as follows:

Proposal 1. — Approval of the Merger Agreement

To approve the Merger Agreement. The Merger Agreement was approved by a vote of the shareholders as follows:

Proposal 2. — Approval of the Elimination of the 20% Voting Cap in Pentair-Ireland’s Articles of Association

To approve the removal of the restriction on voting shares in excess of 20% less one share of the share capital of Pentair-Ireland contained in Pentair-Ireland’s articles of association to be adopted in connection with the Merger. The proposal was approved by a vote of the shareholders as follows:

Proposal 3. — Approval of the Creation of Distributable Reserves of Pentair-Ireland

To approve the reduction of the share premium of Pentair-Ireland to allow the creation of distributable reserves of Pentair-Ireland. The proposal was approved by a vote of the shareholders as follows:

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized, on May 20, 2014.

PENTAIR LTD.

Exhibit Index to Current Report on Form 8-K

Dated May 20, 2014