Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenues [Abstract]
Sales to external customers	$ 1,429,456	$ 1,444,441	$ 1,339,541
Cost of Revenue [Abstract]
Cost of product sales and services	(979,653)	(1,018,479)	(934,808)
Gross profit	449,803	425,962	404,733
Operating Expenses [Abstract]
General and administrative expense	(192,597)	(217,013)	(193,816)
Sales and marketing expense	(136,167)	(138,936)	(136,009)
Research and development expense	(13,198)	(15,300)	(15,877)
Total operating expenses	(341,962)	(371,249)	(345,702)
Other operating income	61,662	5,613	8,406
Other operating expense	(1,055)	(654)	(591)
Income before interest expense and income taxes	168,448	59,672	66,846
Interest expense	(46,682)	(58,556)	(57,580)
Income before income taxes	121,766	1,116	9,266
Income tax expense	(7,371)	(9,587)	(1,382)
Net income (loss)	114,395	(8,471)	7,884
Net income attributable to non‑controlling interest	746	1,052	1,749
Net income (loss) attributable to Evoqua Water Technologies Corp.	$ 113,649	$ (9,523)	$ 6,135
Basic income (loss) per common share	$ 0.97	$ (0.08)	$ 0.05
Diluted income (loss) per common share	$ 0.94	$ (0.08)	$ 0.05
Product
Revenues [Abstract]
Sales to external customers	$ 839,857	$ 851,161	$ 802,302
Cost of Revenue [Abstract]
Cost of product sales and services	(588,264)	(615,171)	(582,606)
Service
Revenues [Abstract]
Sales to external customers	589,599	593,280	537,239
Cost of Revenue [Abstract]
Cost of product sales and services	$ (391,389)	$ (403,308)	$ (352,202)