Share-Based Compensation (Details) - USD ($)						3 Months Ended		9 Months Ended
	Apr. 01, 2020	Nov. 02, 2019	Oct. 01, 2019	Dec. 21, 2018	Nov. 02, 2017	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Feb. 18, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value, exercises in period								$ 26,051,000
Employee Stock Ownership Plan (ESOP), Shares in ESOP				11,297,000
Common stock, par value (in USD per share)						$ 0.01		$ 0.01			$ 0.01
Non-cash share-based compensation						$ 2,520,000	$ 4,978,000	$ 8,504,000	$ 14,248,000
Share-based Compensation expense						2,542,000	4,985,000	8,559,000	14,308,000
Compensation cost not yet recognized, period for recognition						11,972,000		11,972,000
Fair value of options vested								3,673,000
Proceeds from issuance of common stock						$ 2,579,000	0	$ 17,949,000	341,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity incentive plan, number of shares authorized (shares)						5,100,000		5,100,000		5,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant						5,963,000		5,963,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity incentive plan, number of shares authorized (shares)						11,083,000		11,083,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant						1,704,000		1,704,000
Compensation cost not yet recognized, period for recognition						$ 10,140,000		$ 10,140,000
Period for recognition for unrecognized compensation expense								2 years 3 months 18 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition for unrecognized compensation expense								2 years 10 months 24 days
Aggregate value					$ 25,000
Vested in period (shares)		1,159,000			1,197,000			1,554,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Ownership Plan (ESOP), Shares in ESOP				5,000,000
Common stock, par value (in USD per share)				$ 0.01
Employee Stock Ownership Plan (ESOP), Compensation Expense							$ 0	$ 227,000	$ 293,000
Shares issued under ESPP	71		56,000
Evoqua Water Technologies Corp. Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting percentage						25.00%
Expiration period						10 years
Treasury Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld related to net share settlement (including tax withholdings) (shares)		419,000				1,000	138,000	531,000	569,000