Organization (Details) $ in Millions	12 Months Ended
Sep. 30, 2023 USD ($) employee business_segments	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Entity Number of Employees \| employee	3,200
Percentage of Employees Covered by Collective Bargaining Agreements	0.58
Organization	Organization Mueller Water Products, Inc., a Delaware corporation, together with its consolidated subsidiaries, operates in two business segments: Water Flow Solutions and Water Management Solutions. These segments are based on a management reorganization that became effective October 1, 2021; prior period information was recast to conform to the current presentation. Water Flow Solutions’ portfolio includes iron gate valves, specialty valves and service brass products. Water Management Solutions’ portfolio includes fire hydrants, repair and installation, natural gas, metering, leak detection, and pressure management and control products and solutions. The “Company,” “we,” “us” or “our” refers 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 have approximately 3,200 employees globally, of which approximately 58% of our United States hourly workers are covered by collective bargaining agreements. 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. During the year ended September 30, 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. We concluded that the effect of this change was not material to the financial statements. 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. These reclassifications primarily relate to a change in our reportable segments as described in Note 14. 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 underlying 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 within Other noncurrent liabilities as a result of its redemption features. Direct costs associated with Wells Fargo’s capital contribution were 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 are being 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 and were immaterial to the consolidated financial statements.
Number of Reportable Segments \| business_segments	2
Proceeds from Other Equity	$ 0.0	$ 0.0	$ 3.9
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
Other Sundry Liabilities, Noncurrent	$ 3.9

Organization (Details)
$ in Millions

12 Months Ended

Sep. 30, 2023

USD ($)

employee

business_segments

Sep. 30, 2022

USD ($)

Sep. 30, 2021

USD ($)

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Entity Number of Employees | employee

3,200

Percentage of Employees Covered by Collective Bargaining Agreements

0.58

Organization

Mueller Water Products, Inc., a Delaware corporation, together with its consolidated subsidiaries, operates in two business segments: Water Flow Solutions and Water Management Solutions. These segments are based on a management reorganization that became effective October 1, 2021; prior period information was recast to conform to the current presentation. Water Flow Solutions’ portfolio includes iron gate valves, specialty valves and service brass products. Water Management Solutions’ portfolio includes fire hydrants, repair and installation, natural gas, metering, leak detection, and pressure management and control products and solutions. The “Company,” “we,” “us” or “our” refers 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 have approximately 3,200 employees globally, of which approximately 58% of our United States hourly workers are covered by collective bargaining agreements.

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. During the year ended September 30, 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. We concluded that the effect of this change was not material to the financial statements.

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. These reclassifications primarily relate to a change in our reportable segments as described in Note 14.

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 underlying 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 within Other noncurrent liabilities as a result of its redemption features.

Direct costs associated with Wells Fargo’s capital contribution were 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 are being 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 and were immaterial to the consolidated financial statements.

Number of Reportable Segments | business_segments

Proceeds from Other Equity

$ 0.0

$ 3.9

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

Other Sundry Liabilities, Noncurrent

$ 3.9