Suffolk County, NY
drinking water quality
1,535,909 residents · 151 public water systems · 108 ZIP codes
EPA sampled 10 of 151 public water systems here, together serving about 1,344,004 people. The highest reading was PFOS at 17.4 ng/L at Suffolk County Water Authority. 3 of the sampled systems were above a federal limit. Last sampled 9/9/2024.
What was found
| Compound | Highest result | Federal limit | Ratio |
|---|---|---|---|
| PFOS | 17.4 ng/L | 4 ng/L | 4.3× |
| PFOA | 6.5 ng/L | 4 ng/L | 1.6× |
| PFHxS | 10.8 ng/L | 10 ng/L | 1.1× |
| PFNA | 5.7 ng/L | 10 ng/L | 0.6× |
Also detected, with no federal limit set: PFHxA (43.5 ng/L), PFPeA (39.4 ng/L), 6:2 FTS (23.6 ng/L), PFBA (12.6 ng/L).
Health-based violations
Separately from PFAS, EPA records 49 health-based violations across 42 of the county’s water systems since 2020, the most recent in 2025. They involved contaminant 2805, contaminant 2806, contaminant 1017, contaminant 1032, nitrite, total coliform.
What this means
PFAS are industrial chemicals that EPA describes as breaking down only very slowly in the environment. In April 2024 EPA set the first enforceable national limits: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA and GenX.
These figures are county-level and come from EPA’s sampling of public water systems. They describe the worst result found in the county, not what comes out of any particular tap — that depends on which system serves the address, and on the plumbing in the building. A private well is not covered by this programme at all.
ZIP codes in Suffolk County
06390 · 11701 · 11702 · 11703 · 11704 · 11705 · 11706 · 11713 · 11715 · 11716 · 11717 · 11718 · 11719 · 11720 · 11721 · 11722 · 11724 · 11725 · 11726 · 11727 · 11729 · 11730 · 11731 · 11733 · 11735 · 11738 · 11739 · 11740 · 11741 · 11742 · 11743 · 11746 · 11747 · 11749 · 11751 · 11752 · 11754 · 11755 · 11757 · 11763 · 11764 · 11766 · 11767 · 11768 · 11769 · 11770 · 11772 · 11776 · 11777 · 11778 · 11779 · 11780 · 11782 · 11784 · 11786 · 11787 · 11788 · 11789 · 11790 · 11792 · 11794 · 11795 · 11796 · 11798 · 11901 · 11930 · 11931 · 11932 · 11933 · 11934 · 11935 · 11937 · 11939 · 11940 · 11941 · 11942 · 11944 · 11946 · 11947 · 11948 · 11949 · 11950 · 11951 · 11952 · 11953 · 11954 · 11955 · 11956 · 11957 · 11958 · 11959 · 11960 · 11961 · 11962 · 11963 · 11964 · 11965 · 11967 · 11968 · 11970 · 11971 · 11972 · 11973 · 11975 · 11976 · 11977 · 11978 · 11980
Readings are county-level, so every ZIP here shares the figure above. Search your ZIP on the map to see it in context.