Unaudited Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Revenues [Abstract]
Revenue from product sales and services	$ 333,690	$ 299,901	$ 630,740	$ 579,773
Cost of Revenue [Abstract]
Cost of product sales and services	(225,693)	(205,568)	(434,364)	(403,372)
Gross profit	107,997	94,333	196,376	176,401
Operating Expenses [Abstract]
General and administrative expense	(44,742)	(40,211)	(83,807)	(89,397)
Sales and marketing expense	(34,330)	(36,690)	(68,571)	(71,783)
Research and development expense	(4,021)	(5,086)	(8,674)	(10,091)
Other operating (expense) income	904	(365)	311	1,309
Interest expense	(10,810)	(11,898)	(28,053)	(26,651)
Income (loss) before income taxes	14,998	83	7,582	(20,212)
Income tax benefit (expense)	(2,018)	4,812	2,393	11,907
Net income (loss)	12,980	4,895	9,975	(8,305)
Net income attributable to non‑controlling interest	477	1,697	1,185	2,096
Net income (loss) attributable to Evoqua Water Technologies Corp.	$ 12,503	$ 3,198	$ 8,790	$ (10,401)
Basic (loss) earnings per common share (in dollars per share)	$ 0.11	$ 0.03	$ 0.08	$ (0.10)
Diluted (loss) earnings per common share (in dollars per share)	$ 0.10	$ 0.03	$ 0.07	$ (0.10)