Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Revenues [Abstract]
Revenue from product sales and services	$ 348,628	$ 333,690	$ 671,630	$ 630,740
Cost of Revenue [Abstract]
Cost of product sales and services	(253,017)	(225,693)	(487,289)	(434,364)
Gross profit	95,611	107,997	184,341	196,376
Operating Expenses [Abstract]
General and administrative expense	(48,215)	(44,742)	(103,046)	(83,807)
Sales and marketing expense	(35,435)	(34,330)	(71,587)	(68,571)
Research and development expense	(3,957)	(4,021)	(8,103)	(8,674)
Total operating expenses	(87,607)	(83,093)	(182,736)	(161,052)
Other operating income	3,651	937	3,879	937
Other operating expense	(187)	(33)	(375)	(626)
Interest expense	(14,474)	(10,810)	(28,917)	(28,053)
(Loss) income before income taxes	(3,006)	14,998	(23,808)	7,582
Income tax benefit (expense)	4,579	(2,018)	9,093	2,393
Net income (loss)	1,573	12,980	(14,715)	9,975
Net income attributable to non‑controlling interest	189	477	631	1,185
Net income (loss) attributable to Evoqua Water Technologies Corp.	$ 1,384	$ 12,503	$ (15,346)	$ 8,790
Basic loss per common share (in dollars per share)	$ 0.01	$ 0.11	$ (0.13)	$ 0.08
Diluted loss per common share (in dollars per share)	$ 0.01	$ 0.10	$ (0.13)	$ 0.07
Revenue from product sales
Revenues [Abstract]
Revenue from product sales and services	$ 206,868	$ 204,364	$ 386,956	$ 371,488
Cost of Revenue [Abstract]
Cost of product sales and services	(153,857)	(133,830)	(290,452)	(249,636)
Revenue from service
Revenues [Abstract]
Revenue from product sales and services	141,760	129,326	284,674	259,252
Cost of Revenue [Abstract]
Cost of product sales and services	$ (99,160)	$ (91,863)	$ (196,837)	$ (184,728)