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): August 20, 2012 (August 17, 2012)

Commission file number 000-04689

Pentair, Inc.

(Exact name of Registrant as specified in its charter)

Registrant’s telephone number, including area code: (763) 545-1730

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:

On August 17, 2012, Tyco Flow Control International Ltd. (“Tyco Flow Control”) filed an amendment to its Registration Statement on Form S-1 (Registration No. 333-181253) that Tyco Flow Control originally filed with the Securities and Exchange Commission on May 8, 2012 to include Tyco Flow Control financial information for the quarter ended June 29, 2012 (the “Amendment”). Pentair, Inc. (“Pentair”) is filing certain excerpts from the Amendment as Exhibit 99.1 to this Current Report on Form 8-K, which is incorporated herein by reference, for the purpose of making such excerpts available to Pentair’s shareholders. See “Item 9.01 Financial Statements and Exhibits.”

Exhibit 99.1 contains certain “forward-looking statements” regarding business strategies, market potential, future financial performance and other matters with respect to both Tyco Flow Control and Pentair. Without limitation, words such as “targets”, “plans”, “believes”, “expects”, “intends”, “will”, “likely”, “may”, “anticipates”, “estimates”, “projects”, “should”, “would”, “expect”, “positioned”, “strategy”, “future” or words, phrases or terms of similar substance or the negative thereof, are forward-looking statements. The forward looking statements included in Exhibit 99.1 are made only as of the date hereof. These forward looking statements are based on Tyco Flow Control’s and Pentair’s management’s current expectations and beliefs about future events. As with any projection or forecast, they are inherently susceptible to uncertainty and changes in circumstances. Except for the ongoing obligations to disclose material information under the U.S. federal securities laws, neither Tyco Flow Control, Pentair nor Tyco International Ltd. (“Tyco”) are under any obligation to, and expressly disclaim any obligation to, update or alter any forward-looking statements whether as a result of such changes, new information, subsequent events or otherwise.

Various factors could adversely affect Tyco Flow Control’s and Pentair’s operations, business or financial results in the future and cause Tyco Flow Control’s and Pentair’s actual results to differ materially from those contained in the forward-looking statements, including those factors discussed in detail in “Risk Factors” beginning on page 25 of the Amendment. Tyco Flow Control’s and Pentair’s actual results could differ materially from management’s expectations because of these factors, including:

These factors should not be construed as exhaustive and should be read in conjunction with the other cautionary statements that are included in the Amendment. If one or more of these or other risks or uncertainties materialize, or if Tyco Flow Control’s or Pentair’s underlying assumptions prove to be incorrect, actual results may vary materially from what Tyco Flow Control or Pentair projected. Consequently, actual events and results may vary significantly from those included in or contemplated or implied by Tyco Flow Control’s or Pentair’s forward-looking statements.

(a) Not applicable.

(b) Not applicable.

(c) Not applicable.

(d) Exhibits. The following exhibit is being filed herewith:

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, thereunto duly authorized, on August 20, 2012.

PENTAIR, INC.

Exhibit Index to Current Report on Form 8-K

Dated August 20, 2012