Cover - $ / shares	3 Months Ended
	Dec. 31, 2020	Jan. 31, 2021	Sep. 30, 2020
Cover [Abstract]
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Type	10-Q
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-38272
Entity Registrant Name	EVOQUA WATER TECHNOLOGIES CORP.
Entity Tax Identification Number	46-4132761
Entity Address, Address Line One	210 Sixth Avenue
Entity Address, Postal Zip Code	15222
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
City Area Code	724
Local Phone Number	772-0044
Trading Symbol	AQUA
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		119,650,959
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2021
Entity Central Index Key	0001604643
Current Fiscal Year End Date	--09-30