Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Numerator for basic and diluted earnings per common share—Net income attributable to Evoqua Water Technologies Corp.	$ 7,330	$ 5,036	$ 13,317	$ 11,469
Denominator:
Denominator for basic net income per common share—weighted average shares	120,942	118,882	120,785	118,882
Effect of dilutive securities:
Share‑based compensation	4,012	3,041	4,145	3,393
Denominator for diluted net income per common share—adjusted weighted average shares	124,954	121,923	124,930	122,275
Basic income per common share	$ 0.06	$ 0.04	$ 0.11	$ 0.10
Diluted income per common share	$ 0.06	$ 0.04	$ 0.11	$ 0.09