Use these links to rapidly review the document
TABLE OF CONTENTS

As filed with the Securities and Exchange Commission on January 12, 2015.

Registration No. 333-            

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

---

FORM S-3
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

---

ECOLAB INC.

---

(Exact Name of Registrant as Specified in Its Charter)

370 Wabasha Street North
St. Paul, Minnesota 55102
(800) 232-6522
(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant's Principal Executive Offices)

---

James J. Seifert, Esq.
Executive Vice President, General Counsel and Secretary
Ecolab Inc.
370 Wabasha Street North
St. Paul, Minnesota 55102
(651) 250-2981
(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

---

---

Approximate date of commencement of proposed sale to the public:
From time to time after the effective date of this registration statement.

          If the only securities being registered on this form are being offered pursuant to dividend or interest reinvestment plans, check the following box.    o

          If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.    ý

          If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

          If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

          If this form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.    ý

          If this form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.    o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company.

CALCULATION OF REGISTRATION FEE

(1)

An indeterminate aggregate initial offering price and amount of debt securities is being registered as may from time to time be offered at indeterminate prices.

(2)

In accordance with Rules 456(b) and 457(r) under the Securities Act, the registrant is deferring payment of all of the registration fee.

   

---

Table of Contents

Prospectus

Debt Securities

        We may offer debt securities from time to time, in one or more offerings. We will provide the specific terms of any offering and debt securities in supplements to this prospectus. Any prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and the accompanying prospectus supplement carefully before you make your investment decision.

        We may offer and sell debt securities on an immediate, continuous or delayed basis directly to investors or to or through underwriters, dealers or agents, or through a combination of these methods.

        This prospectus may not be used to sell securities unless accompanied by a prospectus supplement which will describe the method and terms of the offering.

        Investing in debt securities involves risks. You should carefully read and consider the risk factors included in our periodic reports, in the prospectus supplement relating to any specific offering of debt securities and in other documents that we file with the Securities and Exchange Commission (the "SEC"). See "Risk Factors" on page 2 of this prospectus.

        Neither the SEC nor any state securities commission has approved or disapproved of the notes or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

   

The date of this prospectus is January 12, 2015.

---

Table of Contents

TABLE OF CONTENTS

---

Table of Contents

ABOUT THIS PROSPECTUS

        This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission (the "SEC") using a "shelf" registration process. Under this shelf registration process, Ecolab may, from time to time, sell debt securities as described in this prospectus, in one or more offerings. This prospectus provides you with a general description of, among other things, the debt securities that Ecolab may offer. Each time that debt securities are sold, a prospectus supplement or free writing prospectus containing specific information about the terms of that offering and the particular debt securities will be provided. The prospectus supplement or free writing prospectus may also add, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the heading "Where You Can Find More Information."

        You should rely only on the information contained or incorporated by reference in this prospectus, the prospectus supplement and in any free writing prospectus issued by us. We have not authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. Ecolab is not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information in this prospectus is accurate as of any date other than the date of this prospectus.

        Unless otherwise stated or the context otherwise requires, references in this prospectus to "Ecolab," "we," "our," "us," "the Company" or similar references are to Ecolab Inc. and its consolidated subsidiaries, which, prior to December 1, 2011, did not include Nalco Holding Company and its subsidiaries and, since December 1, 2011, has included Nalco Holding Company and its subsidiaries. References to "Nalco" refer to Nalco Holding Company and its consolidated subsidiaries.

RISK FACTORS

        Investing in debt securities involves risks. Before investing in debt securities, in addition to the other information, documents or reports included or incorporated by reference into this prospectus and any prospectus supplement or other offering materials, you should carefully consider the risk factors in the section entitled "Risk Factors" in any prospectus supplement, in our most recent Annual Report on Form 10-K and any Quarterly Reports on Form 10-Q and Current Reports on Form 8-K filed subsequent to such Annual Report on Form 10-K, as the same may be amended, supplemented or superseded from time to time by our filings under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and in our other filings with the SEC. These risks could materially and adversely affect our business, financial condition or operating results and could result in a partial or complete loss of your investment.

WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any reports, statements or other information we file with the SEC, including the registration statement of which this prospectus is a part, at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You may obtain information about the operation of the SEC Public Reference Room in Washington, D.C. by calling the SEC at (800) 732-0330. Our filings are also available to the public from the website maintained by the SEC at http://www.sec.gov. Our common stock is listed and traded on the New York Stock Exchange (the "NYSE") under the trading symbol "ECL." Our reports, proxy statements and other information can also be read at the offices of the NYSE, 20 Broad Street, New York, New York 10005.

        The SEC's rules allow us to "incorporate by reference" information into this prospectus, which means that we can disclose important information to you by referring you to other documents that we have filed separately with the SEC. The information incorporated by reference is deemed to be part of

2

---

Table of Contents

this prospectus. Information that we file subsequent to the date of this prospectus with the SEC will automatically update and supersede the information contained in documents filed earlier with the SEC or contained in this prospectus. We incorporate by reference into this prospectus the documents listed below and any future filings made by us with the SEC under Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act after the initial filing of this registration statement that contains this prospectus and prior to the time that we sell all of the securities offered by this prospectus:

•

our Annual Report on Form 10-K for the year ended December 31, 2013;



•

our Quarterly Reports on Form 10-Q for the periods ended March 31, 2014, June 30, 2014 and September 30, 2014; and



•

our Current Reports on Form 8-K filed on February 27, 2014, April 14, 2014, May 9, 2014 and December 3, 2014.

        In addition, the following is also incorporated by reference into this prospectus: (i) the audited consolidated balance sheet of Nalco as of December 31, 2010 and the consolidated statements of operations, equity and cash flows of Nalco for the year ended December 31, 2010, and notes related thereto and (ii) the unaudited condensed consolidated balance sheet of Nalco as of September 30, 2011 and the condensed consolidated statements of operations and cash flows of Nalco for the three and nine-month periods ended September 30, 2011 and 2010, and notes related thereto, each of which is included as an exhibit to our Current Report on Form 8-K filed on December 2, 2011.

        We do not incorporate by reference any information furnished pursuant to Items 2.02 or 7.01 of Form 8-K in any future filings, unless specifically stated otherwise. You may obtain copies, without charge, of documents incorporated by reference in this prospectus, by requesting them in writing or orally. To receive any such copy, call or write:

Ecolab Inc.
370 Wabasha Street North
St. Paul, Minnesota 55102
Attn: Corporate Secretary
1-800-232-6522

        Exhibits to the filings will not be sent, unless those exhibits have been specifically incorporated by reference in this prospectus.

        General information about Ecolab, including our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, as well as any amendments and exhibits to those reports, are available free of charge through our website at www.ecolab.com/investor as soon as reasonably practicable after we file them with, or furnish them to, the SEC. Information on our website is not incorporated into this prospectus or our other securities filings.

FORWARD-LOOKING STATEMENTS

        This prospectus, and the documents incorporated herein by reference, may contain "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Exchange Act that are subject to risks, uncertainties and other factors that could cause actual results to differ materially from those of such forward-looking statements. Additionally, we or our representatives may, from time to time, make other written or verbal forward-looking statements. In this prospectus, and the documents incorporated by reference herein, we discuss expectations regarding our business, financial condition and results of operations. Without limiting the foregoing, words or phrases such as "will likely result," "are expected to," "will continue," "is anticipated," "we believe," "we expect," "estimate," "project" (including the negative or variations thereof) or similar terminology, generally identify forward-looking statements.

3

---

Table of Contents

Forward-looking statements may also represent challenging goals for us. These statements, which represent our expectations or beliefs concerning various future events, are based on current expectations that involve a number of risks and uncertainties that could cause actual results to differ materially from those of such forward-looking statements. We caution that undue reliance should not be placed on forward-looking statements, which speak only as of the date made.

        Additional risks and uncertainties that may affect operating results and business performance are set forth under Item 1A of Ecolab's Annual Report on Form 10-K for the year ended December 31, 2013 and Quarterly Reports on Form 10-Q for the periods ended March 31, 2014, June 30, 2014 and September 30, 2014, which are incorporated by reference herein, and include:

•

the continued vitality of the markets we serve, including oil and gas drilling, completion and stimulation; oil and gas production; and refinery and petrochemical plant markets served by our Global Energy segment, which may be impacted by substantial fluctuations in oil and gas prices;



•

the impact of worldwide economic factors such as the economy, capital flows, interest rates and foreign currency risk;



•

our ability to complete the integration of the businesses of Ecolab, Nalco and Champion and to fully realize the anticipated benefits of these transactions;



•

our dependence on key personnel to lead our business;



•

our ability to execute on key business initiatives including investments in ERP systems to integrate and streamline our processes and to improve our competitiveness;



•

information technology system failures, network disruptions and breaches in data security;



•

political, economic and legal risks relating to our non-U.S. operations;



•

the costs and effects of complying with laws and regulations relating to the environment, including evolving climate change standards, and to the manufacture, storage, distribution, sale and use of our products, as well as to the conduct of our business generally, including employment and labor laws;



•

the lawsuits in which our subsidiaries are defendants which could expose us to monetary damages or settlement costs;



•

claims relating to products and services we supply, including pending claims relating to the use of our products during the response to the Deepwater Horizon oil spill;



•

our ability to develop competitive advantages through value, innovation and customer support;



•

fluctuations in the supply or cost of raw materials and delivered products;



•

future events may impact our deferred tax position, including the utilization of foreign tax credits and undistributed earnings of international affiliates that are considered to be reinvested indefinitely;



•

our indebtedness which will impact our financial flexibility;



•

the ability to acquire and effectively integrate complementary businesses;



•

restraints on pricing flexibility due to contractual obligations;



•

public health outbreaks;



•

we incur significant expenses related to the amortization of intangible assets and may be required to report losses resulting from the impairment of goodwill or other assets recorded, each in connection with completed or future acquisitions;

4

---

Table of Contents

•

the recoverability of deferred tax assets;



•

chemical spills or releases;



•

the occurrence of litigation or claims;



•

the loss or insolvency of a major customer or distributor;



•

acts of war, terrorism or hostilities, natural or man-made disasters, water shortages or severe weather conditions which impact our markets; and



•

other uncertainties or risks reported from time to time in our reports to the SEC.

        You should carefully consider all of the information in or incorporated by reference in this prospectus and any accompanying prospectus supplement prior to investing in debt securities. Additional risk factors may be included in a prospectus supplement or free writing prospectus relating to a particular series or offering of debt securities. Except as may be required under applicable law, we undertake no duty to update our forward-looking statements.

ECOLAB INC.

        With 2013 sales of $13.3 billion, we are the global leader in water, hygiene and energy technologies and services that protect people and vital resources. We deliver comprehensive programs and services to promote safe food, maintain clean environments, optimize water and energy use and improve operational efficiencies for customers in the food, energy, healthcare, industrial and hospitality markets in more than 170 countries. Our cleaning and sanitizing programs and products, pest elimination services, and equipment maintenance and repair services support customers in the foodservice, food and beverage processing, hospitality, healthcare, government and education, retail, textile care and commercial facilities management sectors. Our chemicals and technologies are also used in water treatment, pollution control, energy conservation, oil production and refining, steelmaking, papermaking, mining and other industrial processes.

        Our principal executive offices are located at 370 Wabasha Street North, St. Paul, Minnesota 55102. Our telephone number at our principal executive offices is 1-800-232-6522. Our Internet website address is www.ecolab.com. The information contained on our website is not incorporated by reference in this prospectus.

USE OF PROCEEDS

        Unless otherwise indicated in the applicable prospectus supplement or other offering material, we intend to use the net proceeds from the sale of our debt securities for general corporate purposes. General corporate purposes may include repayment of debt, repurchase of shares of our common stock, capital expenditures, acquisitions and any other purposes that may be stated in any prospectus supplement. The net proceeds may be invested temporarily or applied to repay short-term or revolving debt until they are used for their stated purpose.

RATIO OF EARNINGS TO FIXED CHARGES

        The following table sets forth our ratio of earnings to fixed charges for the periods indicated:

5

---

Table of Contents

DESCRIPTION OF DEBT SECURITIES

        As used in this "Description of Debt Securities" section of this prospectus, debt securities means the debentures, notes, bonds and other evidences of indebtedness that we may issue from time to time. As used in this "Description of Debt Securities" section of this prospectus, references to "Ecolab," "we," "our," "us," "the Company" or similar references are to Ecolab Inc., the issuer of the debt securities. We may offer secured or unsecured debt securities which may be senior or subordinated and which may be convertible or non-convertible. Unless otherwise specified in the applicable prospectus supplement or free writing prospectus, debt securities will be issued in one or more series under an indenture to be entered into between Ecolab Inc. and Wells Fargo Bank, National Association, as trustee, a form of which indenture is filed as an exhibit to the registration statement of which this prospectus is a part.

        The following description briefly summarizes certain general terms and provisions of the debt securities. The particular terms of the debt securities offered by any prospectus supplement or free writing prospectus and the extent, if any, to which the general terms and provisions described below may apply to such debt securities will be described in the applicable prospectus supplement or free writing prospectus. The terms of the debt securities will include those set forth in the applicable indenture and the applicable indenture supplement or company order, if any, and those made a part of the applicable indenture by the Trust Indenture Act of 1939, as amended. You should read the description below, the applicable prospectus supplement or free writing prospectus and the provisions of the applicable indenture and the applicable indenture supplement or company order, if any, in their entirety before investing in any of the debt securities. The statements and descriptions in this prospectus or in any prospectus supplement regarding terms and provisions of the applicable indenture, any applicable indenture supplement or company order and any debt securities are summaries thereof, do not purport to be complete and are subject to, and qualified in their entirety by reference to, all of the provisions of the applicable indenture and any such supplements, company orders and debt securities, including the definitions therein of certain terms.

        Unless otherwise stated in the applicable prospectus supplement or free writing prospectus, the aggregate principal amount of debt securities that may be issued under the applicable indenture is unlimited. The debt securities may be issued in one or more series as may be authorized from time to time. The prospectus supplement or free writing prospectus relating to any series of debt securities will describe the specific terms of such debt securities. Unless otherwise stated in the applicable prospectus supplement or free writing prospectus, the issuer of debt securities of a particular series may issue additional debt securities of such series without the consent of the holders of the debt securities of such series or any other series outstanding at the time of issuance. Any such additional debt securities, together with all other outstanding debt securities of that series, will constitute a single series of securities under the applicable indenture.

        United States federal income tax consequences and special considerations, if any, applicable to any such series will be described in the applicable prospectus supplement or free writing prospectus. Unless otherwise stated in the applicable prospectus supplement or free writing prospectus, the debt securities will not be listed on any securities exchange.

        We expect the debt securities to be issued in fully registered form without coupons. Subject to the limitations provided in the applicable indenture and in the applicable prospectus supplement or other offering material, debt securities that are issued in registered form may be transferred or exchanged at the designated corporate trust office of the trustee, without the payment of any service charge, other than any tax or other governmental charge payable in connection therewith.

        Unless otherwise stated in the applicable prospectus supplement or free writing prospectus, the debt securities of a series may be issued in whole or in part in the form of one or more global securities that will be deposited with, or on behalf of, a depositary identified in the applicable

6

---

Table of Contents

prospectus supplement or free writing prospectus. Global securities will be issued in registered form and in either temporary or definitive form. Unless and until it is exchanged in whole or in part for the individual debt securities, a global security may not be transferred except as a whole by the depositary for such global security to a nominee of such depositary or by a nominee of such depositary to such depositary or another nominee of such depositary or by such depositary or any such nominee to a successor of such depositary or a nominee of such successor. The specific terms of the depositary arrangement with respect to any debt securities of a series and the rights of and limitations upon owners of beneficial interests in a global security will be described in the applicable prospectus supplement or other offering material.

        The debt securities and the indentures under which the debt securities are issued will be governed by and construed in accordance with the law of the State of New York.

        We anticipate appointing Wells Fargo Bank, National Association, the trustee under the indenture, to act as the paying agent, conversion agent, registrar and custodian with regard to the debt securities. Wells Fargo Bank, National Association and its affiliates currently provide, and may in the future provide, banking and other services to us and our subsidiaries in the ordinary course of their respective businesses. We may also appoint a different trustee with respect to one or more series of debt securities.

PLAN OF DISTRIBUTION

        We may sell the debt securities being offered hereby in one or more of the following ways from time to time:

•

to underwriters for resale to purchasers;



•

directly to purchasers; or



•

through agents or dealers to purchasers.

        In addition, we may enter into derivative or hedging transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. In connection with such a transaction, the third parties may sell securities covered by and pursuant to this prospectus and an applicable prospectus supplement. If so, the third parties may use securities borrowed from us or others to settle such sales and may use securities received from us to close out any related short positions. We may also loan or pledge securities covered by this prospectus and an applicable prospectus supplement to third parties, who may sell the loaned securities or, in an event of default in the case of a pledge, sell the pledged securities pursuant to this prospectus and the applicable prospectus supplement.

        The specific plan of distribution, including any underwriters, dealers, agents or direct purchasers and their compensation, for any securities offered hereunder will be identified in the applicable prospectus supplement.

        Underwriters, dealers or agents that participate in the offer of securities, or their affiliates, may have engaged or engage in transactions with and perform services for us or our affiliates in the ordinary course of business for which they may have received or receive customary fees and reimbursement of expenses.

        In compliance with the guidelines of the Financial Industry Regulatory Authority, Inc. ("FINRA"), the maximum discount or commission to be received by any FINRA member or independent broker-dealer may not exceed 8% of the aggregate offering price of the securities offered hereunder.

7

---

Table of Contents

LEGAL MATTERS

        The validity of the debt securities offered by this prospectus and any prospectus supplement will be passed upon for us by Skadden, Arps, Slate, Meagher & Flom LLP and for any underwriters or agents by counsel named in the applicable prospectus supplement.

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        With respect to the unaudited financial information of Ecolab Inc. for the three-month periods ended March 31, 2014 and 2013, the six-month periods ended June 30, 2014 and 2013, and the nine-month periods ended September 30, 2014 and 2013, incorporated by reference into this prospectus, PricewaterhouseCoopers LLP reported that they have applied limited procedures in accordance with professional standards for a review of such information. However, their separate reports dated May 8, 2014, August 7, 2014 and October 30, 2014 incorporated by reference herein state that they did not audit and they do not express an opinion on that unaudited financial information. Accordingly, the degree of reliance on their reports on such information should be restricted in light of the limited nature of the review procedures applied. PricewaterhouseCoopers LLP is not subject to the liability provisions of Section 11 of the Securities Act for their reports on the unaudited financial information because those reports are not a "report" or a "part" of the registration statement prepared or certified by PricewaterhouseCoopers LLP within the meaning of Sections 7 and 11 of the Securities Act.

        The financial statements and management's assessment of the effectiveness of internal control over financial reporting (which is included in Management's Report on Internal Control over Financial Reporting) incorporated into this prospectus by reference to the Ecolab Inc. Annual Report on Form 10-K for the year ended December 31, 2013 have been so incorporated in reliance on the report (which contains an explanatory paragraph on the effectiveness of internal control over financial reporting of the Champion business Ecolab acquired as of December 31, 2013) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

EXPERTS

        The consolidated financial statements of Nalco Holding Company and its subsidiaries as of December 31, 2010, and for the year ended December 31, 2010, incorporated into this prospectus by reference to Exhibit 99.5 of Ecolab's Current Report on Form 8-K filed on December 2, 2011, have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

8

---

Table of Contents

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14.    Other Expenses of Issuance and Distribution.

        The following table sets forth the expenses, other than underwriting discounts and commissions, payable by us in connection with the issuance and distribution of the debt securities being registered hereby.

Item 15.    Indemnification of Directors and Officers.

        Subsection (a) of Section 145 of the General Corporation Law of Delaware empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation), by reason of the fact that such person is or was a director, officer, employee or agent of the corporation or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or enterprise, against expenses (including attorneys' fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding if such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interests of the corporation, and with respect to any criminal action or proceeding, had no reasonable cause to believe such person's conduct was unlawful.

        Subsection (b) of Section 145 empowers a corporation to indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that such person acted in any of the capacities set forth above, against expenses actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit if such person acted under similar standards, except that no indemnification may be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or the court in which the action or suit was brought shall determine that, despite the adjudication of liability, the person is fairly and reasonably entitled to indemnity for such expenses which the court shall deem proper.

        Section 145 further provides that, (i) to the extent a present or former director or officer of a corporation has been successful in the defense of any action, suit or proceeding referred to in subsections (a) and (b) of Section 145 or in the defense of any claim, issue or matter therein, the person shall be indemnified against expenses (including attorneys' fees) actually and reasonably

II-1

---

Table of Contents

incurred in connection therewith, (ii) the indemnification provided for by Section 145 shall not be deemed exclusive of any other rights to which the indemnified party may be entitled and (iii) the scope of indemnification extends to directors, officers, employees or agents of a constituent corporation absorbed in a consolidation or merger and persons serving in that capacity at the request of the constituent corporation for another. Section 145 also empowers the corporation to purchase and maintain insurance on behalf of a present or former director or officer of the corporation (among certain other persons) against any liability asserted against or incurred by the person in any such capacity or arising out of the person's status as such, whether or not the corporation would have the power to indemnify the person against such liabilities under Section 145, including liabilities under the Securities Act.

        Article V of Ecolab's By-Laws, as amended, provides for indemnification of Ecolab's officers and directors to the full extent allowed by Delaware law.

        In addition, Article IV of Ecolab's Restated Certificate of Incorporation provides that Ecolab's directors do not have personal liability to Ecolab or its stockholders for monetary damages for any breach of their fiduciary duty as directors, except (1) for a breach of the duty of loyalty, (2) for acts or omissions not in good faith or which involve intentional misconduct or knowing violation of the law, (3) for willful or negligent violations of certain provisions under the General Corporation Law of Delaware imposing certain requirements with respect to stock repurchases, redemptions and dividends or (4) for any transaction from which the director derived an improper personal benefit. Subject to these exceptions, under Article IV, directors do not have any personal liability to Ecolab or its stockholders for any violation of their fiduciary duty.

        Ecolab has directors and officers liability insurance which protects each director or officer from certain claims and suits, including stockholder derivative suits, even where the director may be determined to not be entitled to indemnification under the General Corporation Law of Delaware and claims and suits arising under the Securities Act. The policy may also afford coverage under circumstances where the facts do not justify a finding that the director or officer acted in good faith and in a manner that was in or not opposed to the best interests of Ecolab.

        Ecolab has entered into indemnification agreements with each of its directors. These indemnification agreements provide for the prompt indemnification "to the fullest extent permitted by law" and for the prompt advancement of expenses, including attorneys' fees and other costs, expenses and obligations paid or incurred in connection with investigating, defending, being a witness or participating in (including on appeal) any threatened, pending or completed action, suit or proceeding related to the fact that the director is or was a director, officer, employee, trustee, agent or fiduciary of Ecolab or is or was serving at the request of Ecolab as a director, officer, employee, trustee, agent or fiduciary of another corporation, partnership, joint venture, employee benefit plan trust or other enterprise, or by reason of anything done or not done by a director in any such capacity. The indemnification agreements further provide that Ecolab has the burden of proving that a director is not entitled to indemnification in any particular case.

        The foregoing represents a summary of the general effect of the General Corporation Law of Delaware, Ecolab's By-Laws, as amended, and Restated Certificate of Incorporation, Ecolab's directors and officers liability insurance coverage and the indemnification agreements for purposes of general description only.

Item 16.    List of Exhibits.

        A list of exhibits filed herewith is contained in the index to exhibits that immediately precedes such exhibits and is incorporated herein by reference.

II-2

---

Table of Contents

Item 17.    Undertakings.

        (a)   The undersigned registrant hereby undertakes:

        (1)   To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

          (i)  to include any prospectus required by Section 10(a)(3) of the Securities Act;

         (ii)  to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the "Calculation of Registration Fee" table in the effective registration statement; and

        (iii)  to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that paragraphs (i), (ii) and (iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

        (2)   That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

        (3)   To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

        (4)   That, for the purpose of determining liability under the Securities Act to any purchaser:

          (i)  Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

         (ii)  Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5) or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii) or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration

II-3

---

Table of Contents

statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

        (5)   That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

          (i)  Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

         (ii)  Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

        (iii)  The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

        (iv)  Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

        (b)   The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the registrant's annual report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan's annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

        (c)   Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, that the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

II-4

---

Table of Contents

SIGNATURES

        Pursuant to the requirements of the Securities Act, Ecolab Inc. certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of St. Paul, State of Minnesota, on January 12, 2015.

        Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons in the capacities indicated on this 12th day of January, 2015.

---

Table of Contents

EXHIBIT INDEX

---