Cover - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Oct. 30, 2020	Mar. 31, 2020	Sep. 30, 2019
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-38272
Entity Registrant Name	EVOQUA WATER TECHNOLOGIES CORP.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-4132761
Entity Address, Address Line One	210 Sixth Avenue
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15222
City Area Code	724
Local Phone Number	772-0044
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	AQUA
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Common stock, par value (in USD per share)	$ 0.01			$ 0.01
Entity Public Float			$ 807
Entity Common Stock, Shares Outstanding		118,276,418
Documents Incorporated by Reference [Text Block]	Portions of the registrant’s definitive proxy statement (the “Proxy Statement”) for its annual meeting of shareholders to be held in February 2021, are incorporated by reference into Part III of this Report. The Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.
Amendment Flag	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Entity Central Index Key	0001604643
Current Fiscal Year End Date	--09-30