New Hampshire water quality
New Hampshire has 2,269 active public water systems (3,968 on file total), 681 of them graded by TapGraded.
Grade distribution
Biggest water systems
MANCHESTER WATER WORKS
MANCHESTER, NH · 123,500 served
PENNICHUCK WATER WORKS
NASHUA, NH · 88,853 served
CONCORD WATER DEPT
CONCORD, NH · 44,215 served
PORTSMOUTH WATER WORKS
PORTSMOUTH, NH · 33,000 served
KEENE WATER DEPT
KEENE, NH · 30,000 served
DOVER WATER DEPT
DOVER, NH · 29,000 served
MERRIMACK VILLAGE DIST
MERRIMACK, NH · 25,500 served
ROCHESTER WATER DEPT
ROCHESTER, NH · 25,000 served
SALEM WATER DEPT
SALEM, NH · 21,000 served
DERRY WATER DEPT
DERRY, NH · 17,370 served
Lowest-graded systems
Active, graded systems serving at least 10,000 people, ordered by lowest Tap Grade first.
EXETER WATER DEPT
EXETER, NH · 12,236 served
SEABROOK WATER DEPT
SEABROOK, NH · 14,000 served
SALEM WATER DEPT
SALEM, NH · 21,000 served
HUDSON WATER DEPT
HUDSON, NH · 16,700 served
MANCHESTER WATER WORKS
MANCHESTER, NH · 123,500 served
PORTSMOUTH WATER WORKS
PORTSMOUTH, NH · 33,000 served
DERRY WATER DEPT
DERRY, NH · 17,370 served
ROCHESTER WATER DEPT
ROCHESTER, NH · 25,000 served
LEBANON WATER DEPT
LEBANON, NH · 13,600 served
DOVER WATER DEPT
DOVER, NH · 29,000 served
Source: EPA SDWIS/ECHO · Data as of 2026Q2