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Document and Entity Information - shares
 6 Months Ended
Mar. 31, 2021
Apr. 30, 2021
Document And Entity Information [Abstract]    
Document Fiscal Period Focus Q2  
Document Period End Date Mar. 31, 2021  
Document Fiscal Year Focus 2021  
Entity Registrant Name MUELLER WATER PRODUCTS, INC.  
Entity Central Index Key 0001350593  
Current Fiscal Year End Date --09-30  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Entity Current Reporting Status Yes  
Entity Emerging Growth Company false  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   158,525,776
Entity Small Business false  
Trading Symbol MWA  
Title of 12(b) Security Common stock, par value $0.01