56,000 water systems were never in EPA's PFAS survey. Initial monitoring is due April 2027.
The federal PFAS drinking water rule covers 66,415 active community and non-transient non-community water systems. Only 10,257 of them were sampled in EPA's UCMR 5 survey. The other 56,158 have no federal PFAS results on record, and 6,588 of those are schools and daycares that run their own water.
All of them have to complete initial monitoring and get the results to their state by April 26, 2027. That includes the UCMR 5 systems, though most of them can count their survey results. The date is separate from the 2029 compliance date for the limits themselves, and it is not part of either rule change EPA has proposed.
Not all 56,158 are starting from zero. 13,357 of them are in the ten states that set PFAS limits before the federal rule (Massachusetts, Maine, Michigan, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and Wisconsin), and many have sampled under those rules. Systems that buy all their water may be covered by their wholesaler's results, if their state allows it, because a connection that delivers finished water is not an entry point under the rule. For the rest, mostly small groundwater systems in the other 40 states, April 2027 will bring their first PFAS results.
How many samples
Samples are taken at each entry point to the distribution system. The count depends on the source water and the size of the system:
| System | Initial monitoring |
|---|---|
| Groundwater, serving 10,000 or fewer | 2 samples per entry point, 5 to 7 months apart, within 12 months |
| Surface water, groundwater under the influence of surface water, groundwater serving more than 10,000, and blended entry points | 4 quarterly samples per entry point, 2 to 4 months apart, within 12 months |
Samples go to a certified lab using EPA Method 533 or 537.1. The calendar is tighter than it looks. A small groundwater system starting from scratch needs its first sample no later than late November 2026 for the second to land, five months on, before the deadline.
Data you may already have
Your state can let you count earlier results toward initial monitoring if they were collected on or after January 1, 2019 with Method 533 or 537.1, whether under UCMR 5, a state program or another appropriate source. If you have some qualifying results but not enough, you only sample to fill the missing calendar periods. One catch: results analysed before June 25, 2024 that were above the limits don't count, and those sites have to sample again.
Ask your state what it will accept before you book a lab.
What the results decide
Initial results set how often each entry point samples once compliance monitoring begins. If every sample at an entry point is below the trigger levels, which are one-half of each limit (2.0 ppt for PFOA and PFOS), the state can approve sampling once every three years. A single result at or above a trigger level puts that entry point on quarterly sampling. The comparison is per sample, not an average.
What grants will and won't pay for
The obvious place to look is EPA's Emerging Contaminants in Small or Disadvantaged Communities grant (EC-SDC), which is $5 billion over fiscal years 2022 to 2026. But EPA's guidance is explicit that compliance monitoring is not eligible. That covers your initial-monitoring samples.
EC-SDC can pay for:
- Non-routine testing: sampling to find the source or the extent of contamination, beyond what the rule requires.
- Planning and design: action plans, preliminary engineering reports, alternatives analyses, and preliminary and final design. Some design work done before an award may count as a pre-award cost.
- Treatment and other capital projects for systems serving 10,000 or fewer people that can't take on enough debt, or systems that meet the state's disadvantaged-community definition.
Ongoing operation and maintenance is not eligible. FY 2026 is the program's final year, with $945.7 million allotted, and states run their own application rounds. A system that finds PFAS in its initial samples should already know its state's EC-SDC timeline.
The short version
- Find out whether your state will accept results you already have.
- If not, book a certified lab now. Small groundwater systems need their first sample this fall. Look up what your system owes.
- Budget for the monitoring yourself. EC-SDC won't fund it.
- If results come back high, your state's EC-SDC and DWSRF rounds are where design and treatment money comes from. Open rounds by state.
- To see how carbon, ion exchange or a membrane would handle your results, try the treatment bench.
Need a lab for initial monitoring?
Tell us about your system and we'll point you to certified labs that may fit. If your results are already in hand, we can also point you to engineers, treatment firms or funding contacts.
Regulatory status as of October 20, 2026. EPA has proposed rescinding the limits for PFHxS, PFNA and HFPO-DA (GenX) and the hazard index, and extending the PFOA and PFOS compliance date to 2031 for systems that request it. Neither proposal is final, and neither changes the initial monitoring date. System counts are PFAS Comply's analysis of EPA's SDWIS inventory (2026Q2) against the final UCMR 5 data. This is general information, not a compliance determination. Confirm your requirements with your state drinking water program.