Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 51,662	$ 114,395	$ (8,471)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustments	21,672	(2,830)	1,507
Unrealized derivative gain (loss) on cash flow hedges, net of tax	7,293	(4,717)	74
Change in pension liability, net of tax	2,922	79	(5,568)
Total other comprehensive income (loss)	31,887	(7,468)	(3,987)
Less: Comprehensive income attributable to non‑controlling interest	(180)	(746)	(1,052)
Comprehensive income (loss) attributable to Evoqua Water Technologies Corp.	$ 83,369	$ 106,181	$ (13,510)