Floating Rate Notes;”provided, however, that the minimum interest rate on the floating rate notes will not be less than 0.000%. The floating ratenotes will mature on,. The 20notes will bear interest at a rate ofwill bear interest at a rate of% per year and will mature on, . The 20notes will bear interest at a rate of% per year and will. The 20notes will bear interest at a rate of% per year and will mature on,. Interest on the floating ratenotes will be payable quarterly in arrears on,,andof each year starting on, 2026. Interest on the fixed rate notes We may redeem the fixed rate notes of any series at our option, in whole at any time or in part from time to time, at the applicable redemptionprices described under “Description of the Notes — Optional Redemption.” The floating rate notes will not be redeemable prior to maturity, exceptpursuant to a special mandatory redemption as described below. If a change of control repurchase event as described herein occurs with respect to aseries of notes, unless we have exercised our option to redeem the notes of that series, we will be required to offer to repurchase the notes of thatseries at the price described under “Description of the Notes — Offer to Repurchase upon a Change of Control Repurchase Event.” such transaction, the “CoolIT Systems Acquisition”). We intend to use a portion of the net proceeds from this offering to fund the CoolIT SystemsAcquisition. See “Use of Proceeds.” This offering is not contingent on the completion of the CoolIT Systems Acquisition, which, if completed, will occur subsequent to thecompletion of this offering. However, if (i)the CoolIT Systems Acquisition is not completed on or prior to the later of (x)September16, 2026 or(y)such later date to which the end date under the Merger Agreement as in effect on the closing date of this offering may be extended in accordancewith the terms thereof (such later date, the “Special Mandatory Redemption End Date”), (ii)prior to the Special Mandatory Redemption End Date, theMerger Agreement is terminated or (iii)we otherwise notify the trustee that we will not pursue the completion of the CoolIT Systems Acquisition, wewill be required to redeem the floating rate notes, the 20notes, the 20 notes and the 20 notes (collectively, the “SMR notes”), at a specialmandatory redemption price equal to 101% of the principal amount of the SMR notes to be redeemed plus accrued and unpaid interest thereon to, but The notes will be our senior unsecured obligations and will rank equally in right of payment with all of our other senior indebtedness from timeto time outstanding. The notes of each series will be issued only in registered form in denominations of $2,000 and integral multiples of $1,000 inexcess thereof. Investing in the notes involves risks that are described under “Risk Factors” beginning on pageS-6of this prospectus supplement and the risksdiscussed in the documents we file with the U.S. Securities and Exchange Commission. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the notes or passed uponthe adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.Underwritin PriceDiscountexpenses, to UsPer Floating Rate Note%%% TABLE OF CONTENTS Prospectus Supplement No person is authorized to give any information or to make any representations other than thosecontained in or incorporated by reference into this prospectus supplement, the accompanying prospectus andin any free writing prospectus we have authorized, and, if given or made, such information orrepresentations must not be relied upon as having been authorized. Neither the delivery of this prospectussupplement and the accompanying prospectus, nor any sale made hereunder, shall under any circumstances The distribution of this prospectus supplement and the accompanying prospectus and the offering of thenotes in certain jurisdictions may be restricted by law. This prospectus supplement and the accompanyingprospectus do not constitute an offer or a solicitation on our behalf or by the underwriters to subscribe to orpurchase any of the notes, and may not be used for or in connection with an offer or solicitation by anyone, ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which contains the specificterms of this offering of notes and certain other matters relating to Ecolab. The second part is the prospectusdated February23, 2026, which is part of our registration statement on Form S-3 that we filed with theSecurities and Exchange Commission (the “SEC”) and contains more general information about, among This prospectus supplement may add to, update or change the information in the accompanyingprospectus. If information in this prospectus supplement is inconsistent with information in theaccompanying prospectus, this prospectus suppl