Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Numerator for basic and diluted earnings per common share—Net income attributable to Evoqua Water Technologies Corp.	$ 5,987	$ 6,433
Denominator:
Denominator for basic net income per common share—weighted average shares	120,632	117,768
Effect of dilutive securities:
Share‑based compensation	4,315	3,790
Denominator for diluted net income per common share—adjusted weighted average shares	124,947	121,558
Basic income per common share	$ 0.05	$ 0.05
Diluted income per common share	$ 0.05	$ 0.05