Cover Page - shares	9 Months Ended
	Sep. 30, 2024	Oct. 24, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-34112
Entity Registrant Name	Energy Recovery, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	01-0616867
Entity Address, Address Line One	1717 Doolittle Drive
Entity Address, City or Town	San Leandro
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94577
City Area Code	510
Local Phone Number	483-7370
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	ERII
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		57,893,899
Entity Central Index Key	0001421517
Document Fiscal Year Focus	2024
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q3
Amendment Flag	false