Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Revenues [Abstract]
Revenue from product sales and services	$ 346,564	$ 351,663	$ 668,757	$ 697,768
Cost of Revenue [Abstract]
Cost of product sales and services	(240,645)	(240,457)	(467,493)	(480,847)
Gross profit	105,919	111,206	201,264	216,921
Operating Expenses [Abstract]
General and administrative expense	(52,928)	(62,130)	(95,211)	(107,900)
Sales and marketing expense	(33,830)	(33,976)	(67,758)	(71,990)
Research and development expense	(3,393)	(3,189)	(6,516)	(6,873)
Total operating expenses	(90,151)	(99,295)	(169,485)	(186,763)
Other operating income	511	9,518	991	61,238
Other operating expense	(101)	(274)	(358)	(549)
Operating profit (loss)	16,178	21,155	32,412	90,847
Interest expense	(8,395)	(13,252)	(17,068)	(26,835)
Income before income taxes	7,783	7,903	15,344	64,012
Income tax (expense) benefit	(2,701)	7	(3,785)	(2,596)
Net income	5,082	7,910	11,559	61,416
Net income attributable to non‑controlling interest	46	98		459
Net income attributable to Evoqua Water Technologies Corp.	$ 5,036	$ 7,812	$ 11,469	$ 60,957
Basic income per common share	$ 0.04	$ 0.07	$ 0.10	$ 0.52
Diluted income per common share	$ 0.04	$ 0.06	$ 0.09	$ 0.50
Revenue from product sales
Revenues [Abstract]
Revenue from product sales and services	$ 202,466	$ 205,969	$ 382,481	$ 402,529
Cost of Revenue [Abstract]
Cost of product sales and services	(144,521)	(144,156)	(275,582)	(284,612)
Revenue from service
Revenues [Abstract]
Revenue from product sales and services	144,098	145,694	286,276	295,239
Cost of Revenue [Abstract]
Cost of product sales and services	$ (96,124)	$ (96,301)	$ (191,911)	$ (196,235)