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Cover - shares
 9 Months Ended
Sep. 30, 2021
Nov. 01, 2021
Cover [Abstract]    
Entity Registrant Name 374WATER INC.  
Entity Central Index Key 0000933972  
Document Type 10-Q  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Small Business true  
Entity Shell Company false  
Entity Emerging Growth Company false  
Entity Current Reporting Status Yes  
Document Period End Date Sep. 30, 2021  
Entity Filer Category Non-accelerated Filer  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2021  
Entity Common Stock Shares Outstanding   122,817,746
Document Quarterly Report true  
Entity Interactive Data Current Yes  
Document Transition Report false  
Entity File Number 000-27866  
Entity Tax Identification Number 88-0271109  
Entity Incorporation State Country Code DE  
Entity Address Address Line 1 701 W Main Street, Suite 410  
Entity Address City Or Town Durham  
Entity Address State Or Province NC  
Entity Address Postal Zip Code 27701  
City Area Code 919  
Local Phone Number 888-8194