Most sellers assume the well gets checked somewhere inside the home inspection window, filed alongside the roof, the furnace, and the electrical panel. In Westchester County, that assumption costs time. The county's Private Well-Water Testing Law does not wait for a buyer's inspection contingency. It starts the moment both parties sign the contract of sale and runs on its own calendar, one that has nothing to do with when a home hits the market or how thorough a buyer's inspector turns out to be.
For the roughly 6 percent of Westchester households that draw drinking water from a private well, most of them concentrated in the county's northern towns, that separate clock can catch even a seller who has sold homes before.
The clock starts at signing, not at listing
Westchester's Private Well-Water Testing Legislation, Local Law 7 of 2007, was adopted May 23, 2007, and became effective that November. Codified at County Code §707.03, it states plainly that upon contract signing the seller "shall cause a water test to be conducted in the manner established" by the chapter. The seller arranges and pays for it, and has ten days from the date the contract is executed to give the buyer written confirmation that the test has been ordered.
Once results come back from the lab, the seller has five more days to hand them to the buyer. Both sides then certify in writing that they received and reviewed the report. None of this is optional or something a real estate contract can waive away, because the law requires the certified laboratory to send a copy of the results directly to the Westchester County Department of Health regardless of what the buyer and seller agree to privately.
Why the home inspector's water sample doesn't count
Here is where sellers most often lose time. A home inspector may run a general water check as part of the standard inspection, and a buyer may even mail in a self-collection kit out of habit. Neither satisfies the county law. The sample has to be collected by an employee or an authorized representative of a laboratory that is both New York State certified and registered with the Westchester County Health Department to conduct testing under this specific statute. A homeowner cannot collect it. A real estate agent cannot collect it. A generic mail-order water test, however accurate, does not meet the standard.
That distinction matters because the Westchester County Department of Health maintains its own list of registered labs, and only one of those labs can be the one that transmits results to the county electronically. If a seller schedules a test with the wrong provider, the ten-day window can pass before anyone realizes the paperwork won't satisfy the law.
Where this actually shows up on a closing timeline
Private wells aren't spread evenly across Westchester. They cluster in the towns without municipal water districts, concentrated in the northern part of the county. Pound Ridge is the clearest example: the town's own conservation board states that drinking water there comes from private wells on each individual property, since Pound Ridge has no town-run well field or water system of its own. The same geography shows up in the county's own planning data, which puts roughly one-third of Westchester's land area on subsurface septic disposal rather than sewer lines, most of it in the Croton watershed towns of northern Westchester.
If a listing sits in one of these unincorporated, no-town-water pockets, the well law belongs on the closing checklist from day one, not on the list of things to sort out once an offer comes in.
What a typical timeline looks like
| Milestone | Timing |
|---|---|
| Contract of sale signed | Day 0 |
| Seller must confirm test has been ordered | Within 10 days |
| Test performed (home must be occupied or well chlorinated first) | Varies; add 7 days if chlorination is required |
| Lab results returned | Commonly 12 to 14 days after sample collection |
| Seller delivers results to buyer | Within 5 days of receiving them |
If a house has sat vacant for three weeks or more, the well often needs chlorination before a valid sample can be drawn, and the law's own testing guidance notes a sample cannot be taken until seven days after that chlorination. A vacant listing on a private well can add nearly two weeks to a timeline that a seller in a municipal-water neighborhood never has to think about.
What gets tested, and what happens if something fails
Every test under the law covers a set list of primary contaminants: total coliform bacteria, nitrate, arsenic, lead (both first-draw and flushed samples), the primary organic contaminants named in Part 5 of the New York State Sanitary Code, vinyl chloride, and MTBE. If total coliform comes back positive, the lab must also test for fecal coliform or E. coli. A secondary panel covers pH, iron, manganese, sodium, and chloride, which affect taste and appearance rather than safety.
A failure on a primary contaminant carries real consequences. Under the law, the seller can cancel the contract and return the buyer's down payment with neither side liable to the other, or the two parties can agree in writing to close anyway with the purchaser responsible for correcting the condition. Sellers who ignore a known problem face county penalties that start at $1,000 per day until potable water is restored and can reach $10,000 for a violation left unremediated after a month.
Results are not indefinitely reusable. A test that meets every requirement of the law stays valid for one year, except for the coliform result, which is only good for six months. A seller who tested the well eighteen months ago for an unrelated reason will likely need a new sample anyway.
How Westchester's rule compares to its neighbors
Two nearby counties handle the same problem differently, and the difference matters for anyone comparing towns across county lines. Rockland County's version of this law, found in Chapter 389 of its county code, puts the same obligation on the seller: order the test, pay for it, and notify the buyer within roughly the same window. Suffolk County flips the responsibility entirely, requiring the buyer to obtain and pay for the certification before closing can happen. A buyer or seller assuming all three counties work the same way is the most common way this catches people by surprise.
A separate 2026 development worth knowing about
Apart from the mandatory point-of-sale test, Westchester County Executive Ken Jenkins stood at the Alfred B. DelBello Muscoot Farm in Katonah on May 1, 2026, to announce that residents on private wells can now apply for free PFAS testing through a New York State pilot program. Homeowners who qualify and turn up contamination above state drinking water standards can also apply for rebates of up to $5,000 toward a treatment system or up to $10,000 to connect to a public water supply. This program is voluntary and separate from the Private Well-Water Testing Law, whose mandatory panel does not test for PFAS. A seller who takes advantage of the pilot program ahead of listing can walk into contract signing already knowing where the well stands on a contaminant the required sale test simply doesn't cover.
FAQ
Does the sample have to come from untreated water, even if I have a whole-house filter? Yes. If a water softener, filter, or other treatment system is installed, it has to be disconnected or bypassed before the sample is collected, or the sample must be taken ahead of the treatment point.
Can the buyer and seller just agree to skip the test? No. Because the certified lab is required to send results directly to the Westchester County Department of Health, there is no private waiver that satisfies the law, regardless of what the contract says.
I already tested my well for another reason. Can I use those results? Only if the sample was collected and analyzed by a certified lab following every requirement of the law, and only within the one-year window for most parameters or six months for coliform specifically.
If a Westchester listing sits on a private well, the water test deserves a spot on the closing timeline the day the contract is drafted, not a scramble once the buyer's inspection period opens. Nicole Isaacs works with sellers across Westchester's well-water towns to build that timeline in from the start. Let's Connect.
