Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenues [Abstract]
Revenue from product sales and services	$ 322,193	$ 346,105
Cost of Revenue [Abstract]
Cost of product sales and services	(226,848)	(240,390)
Gross profit	95,345	105,715
Operating Expenses [Abstract]
General and administrative expense	(42,283)	(45,770)
Sales and marketing expense	(33,928)	(38,014)
Research and development expense	(3,123)	(3,684)
Total operating expenses	(79,334)	(87,468)
Other operating income	480	51,720
Other operating expense	(257)	(275)
Operating profit (loss)	16,234	69,692
Interest expense	(8,673)	(13,583)
Income before income taxes	7,561	56,109
Income tax expense	(1,084)	(2,603)
Net income	6,477	53,506
Net income attributable to non‑controlling interest	44	361
Net income attributable to Evoqua Water Technologies Corp.	$ 6,433	$ 53,145
Basic income per common share	$ 0.05	$ 0.46
Diluted income per common share	$ 0.05	$ 0.44
Revenue from product sales
Revenues [Abstract]
Revenue from product sales and services	$ 180,015	$ 196,560
Cost of Revenue [Abstract]
Cost of product sales and services	(131,061)	(140,456)
Revenue from service
Revenues [Abstract]
Revenue from product sales and services	142,178	149,545
Cost of Revenue [Abstract]
Cost of product sales and services	$ (95,787)	$ (99,934)