Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues [Abstract]
Revenue from product sales and services	$ 369,681	$ 347,827	$ 1,038,438	$ 1,045,595
Cost of Revenue [Abstract]
Cost of product sales and services	(252,652)	(237,593)	(720,145)	(718,440)
Gross profit	117,029	110,234	318,293	327,155
Operating Expenses [Abstract]
General and administrative expense	(50,837)	(44,867)	(146,048)	(152,767)
Sales and marketing expense	(35,871)	(29,855)	(103,629)	(101,845)
Research and development expense	(3,413)	(2,782)	(9,929)	(9,655)
Total operating expenses	(90,121)	(77,504)	(259,606)	(264,267)
Other operating income	1,662	621	2,653	61,859
Other operating expense	(260)	(285)	(618)	(834)
Operating profit (loss)	28,310	33,066	60,722	123,913
Interest expense	(11,224)	(10,485)	(28,292)	(37,320)
Income before income taxes	17,086	22,581	32,430	86,593
Income tax expense	(3,887)	(740)	(7,672)	(3,336)
Net income	13,199	21,841	24,758	83,257
Net income attributable to non‑controlling interest	44	457		916
Net income attributable to Evoqua Water Technologies Corp.	$ 13,155	$ 21,384	$ 24,624	$ 82,341
Basic income per common share	$ 0.11	$ 0.18	$ 0.21	$ 0.71
Diluted income per common share	$ 0.11	$ 0.18	$ 0.20	$ 0.68
Revenue from product sales
Revenues [Abstract]
Revenue from product sales and services	$ 218,427	$ 207,575	$ 600,908	$ 610,104
Cost of Revenue [Abstract]
Cost of product sales and services	(152,591)	(143,457)	(428,173)	(428,069)
Revenue from service
Revenues [Abstract]
Revenue from product sales and services	151,254	140,252	437,530	435,491
Cost of Revenue [Abstract]
Cost of product sales and services	$ (100,061)	$ (94,136)	$ (291,972)	$ (290,371)