Organization (Details) $ in Millions		12 Months Ended
Organization (Details) $ in Millions	Jul. 31, 2014	Sep. 30, 2021 USD ($) business_segments	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization		Organization Mueller Water Products, Inc., a Delaware corporation, together with its consolidated subsidiaries, operates in two business segments: Infrastructure and Technologies. Infrastructure manufactures valves for water and gas systems, including butterfly, iron gate, tapping, check, knife, plug, automatic control and ball valves, as well as dry-barrel and wet-barrel fire hydrants and pipe repair products. Technologies offers metering systems, leak detection, pipe condition assessment and other products and services for the water infrastructure industry. The “Company,” “we,” “us” or “our” refer to Mueller Water Products, Inc. and its subsidiaries. With regard to the Company’s segments, “we,” “us” or “our” may also refer to the segment being discussed. We sold our Anvil segment on January 6, 2017 and our U.S. Pipe segment on April 1, 2012. We have approximately 3,400 employees globally, of which 66% of our hourly workers are covered by collective bargaining agreements. In July 2014, Infrastructure acquired a 49% ownership in an industrial valve joint-venture for $1.7 million. As a result of substantive control features in the joint-venture agreement, all of the joint venture’s assets, liabilities and results of operations were included in our consolidated financial statements. The noncontrolling interest portion was included in selling, general and administrative expenses. Noncontrolling interest was recorded at its carrying value, which approximated fair value. Infrastructure acquired the remaining 51% noncontrolling interest on October 3, 2019. On December 3, 2018, we completed our acquisition of Krausz Industries Development Ltd. and subsidiaries (“Krausz”). During our 2020 and 2019 fiscal years, we included the financial statements of Krausz on a one-month lag. Refer to Note 5. for additional disclosures. During the three months ended March 31, 2021, we aligned the consolidation of the financial statements of Krausz in the Company’s consolidated financial statements, eliminating the previous inclusion of Krausz financial statements with a one-month reporting lag. In accordance with applicable accounting literature, the elimination of the one-month reporting lag is considered to be a change in accounting principle. We believe this change in accounting principle is preferable as the financial statements of all of our subsidiaries are now reported on the same basis, providing the most current information available. The effect of the elimination of the reporting lag during the year ended September 30, 2021 resulted in an increase of $6.0 million to net sales and an increase of $1.4 million to operating income. We concluded that the effect of this change is not material to the balance sheets, statements of operations, statements of cash flows, net income and earnings per share and therefore have not retrospectively applied this change. On June 14, 2021, we acquired all the outstanding capital stock of i2O Water Ltd (“i2O”) a provider of pressure management solutions to more than 100 water companies in 45 countries. The consolidated balance sheet at September 30, 2021 includes the preliminary estimated fair values of the net assets of i2O. The Company is still reviewing the impact of taxes and certain other items. The results of i2O’s operations and cash flows for the period subsequent to the acquisition are included in the consolidated statement of operations and consolidated statement of cash flows, respectively. Refer to Note 5. for additional disclosures related to the acquisition. Our consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), which require us to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, sales and expenses and the disclosure of contingent assets and liabilities for the reporting periods. Actual results could differ from those estimates. All significant intercompany balances and transactions have been eliminated. Certain reclassifications have been made to previously reported amounts to conform to the current presentation. Unless the context indicates otherwise, whenever we refer to a particular year, we mean our fiscal year ended or ending September 30 in that particular calendar year. New Markets Tax Credit Program On December 22, 2020, we entered into a financing transaction with Wells Fargo Community Investment Holdings, LLC (“Wells Fargo”) related to our brass foundry construction project in Decatur, Illinois under a qualified New Markets Tax Credit program (“NMTC”). The NMTC is a federal program intended to encourage capital investment in qualified lower income communities. Under the NMTC, investors claim federal income tax credits over a period of seven years in connection with qualified investments in the equity of community development entities (“CDE”s), which are privately managed investment institutions that are certified to make qualified low-income community investments, such as in our foundry project. Under the NMTC, Wells Fargo contributed capital of $4.8 million to an investment fund and we loaned $12.2 million to the fund. Wells Fargo is entitled to the associated tax credits, which are subject to 100% recapture if we do not comply with various regulations and contractual provisions surrounding the foundry project. We have indemnified Wells Fargo for any loss or recapture of tax credits related to the transaction until the seven-year period elapses. We do not anticipate any credit recaptures will be required in connection with this arrangement. The investment fund contributed $16.5 million cash for a 99.99% stake in a joint venture (“Sub-CDE”) with a CDE. The Sub-CDE then loaned $16.2 million to us, with the use of the loan proceeds restricted to foundry project expenditures. This transaction also includes a put/call provision under which we may be obligated or entitled to repurchase Wells Fargo’s interest in the investment fund. We believe that Wells Fargo will exercise its put option in December 2027 for nominal consideration, resulting in our becoming the sole owner of the investment fund, cancelling the related loans, and recognizing an estimated gain of $3.9 million. We determined that the investment fund and the Sub-CDE are variable interest entities (“VIEs”) and that we are the primary beneficiary of the VIEs. The ongoing activities of the VIEs, namely collecting and remitting interest and fees and administering NMTC compliance, were contemplated in the initial design of the transaction and are not expected to significantly affect economic performance throughout the life of the VIEs. Additionally, we are obligated to deliver tax benefits and provide various other guarantees to Wells Fargo and to absorb the losses of the VIEs. Wells Fargo does not have a material interest in the underling economics of the project. Consequently, we have included the financial statements of the VIEs in our consolidated financial statements. Intercompany transactions between us and the VIEs have been eliminated in consolidation. Wells Fargo’s contribution to the investment fund is consolidated in our financial statements as an Other noncurrent liability as a result of its redemption features. Direct costs associated with Wells Fargo’s capital contribution have been netted against the recorded proceeds, resulting in a net cash contribution of $3.9 million. Other direct costs associated with the transaction were capitalized and will be recognized as interest expense over the seven-year tax credit period. Incremental costs to maintain the structure during the compliance period are expensed as incurred.
Number of Reportable Segments \| business_segments		2
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	49.00%
Payments to Acquire Interest in Joint Venture			$ 1.7
Proceeds from Other Equity		$ 3.9	$ 0.0	$ 0.0
Proceeds From Other Equity, Gross Amount		4.8
Intercompany Loan Related to NMTC		12.2
Investment Fund Contribution For NMTC		16.5
Sub CDE Loan From NMTC		$ 16.2