Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenues [Abstract]
Revenue from product sales and services	$ 346,105	$ 323,002
Cost of Revenue [Abstract]
Cost of product sales and services	(240,390)	(234,272)
Gross profit	105,715	88,730
Operating Expenses [Abstract]
General and administrative expense	(45,770)	(54,831)
Sales and marketing expense	(38,014)	(36,152)
Research and development expense	(3,684)	(4,146)
Total operating expenses	(87,468)	(95,129)
Other operating income	51,720	228
Other operating expense	(275)	(188)
Operating profit (loss)	69,692	(6,359)
Interest expense	(13,583)	(14,443)
Income (loss) before income taxes	56,109	(20,802)
Income tax (expense) benefit	(2,603)	4,514
Net income (loss)	53,506	(16,288)
Net income attributable to non‑controlling interest	361	442
Net income (loss) attributable to Evoqua Water Technologies Corp.	$ 53,145	$ (16,730)
Basic income (loss) per common share	$ 0.46	$ (0.15)
Diluted income (loss) per common share	$ 0.44	$ (0.15)
Revenue from product sales
Revenues [Abstract]
Revenue from product sales and services	$ 196,560	$ 180,088
Cost of Revenue [Abstract]
Cost of product sales and services	(140,456)	(136,595)
Revenue from service
Revenues [Abstract]
Revenue from product sales and services	149,545	142,914
Cost of Revenue [Abstract]
Cost of product sales and services	$ (99,934)	$ (97,677)