Checking water risk before you buy a house

Before you look

Each check below says what the public maps show, what they miss, and what to ask the seller or the inspector. The address check gives the map facts for one address in Suffolk County in a few seconds, so you can do it for every house on your list before you see it.

Start with the seller's disclosure form

Since March 20, 2024, New York's Property Condition Disclosure Statement asks the seller about flood hazard areas, any FEMA assistance for flood damage, any claim for flood damage filed with an insurer, and any federal requirement to keep flood insurance. Its water question now asks about any water penetration or damage, not only standing water. The $500 credit a seller could once give in place of the form is gone. Read the answers next to the map facts below; where they disagree, ask.

Source: New York State Bar Association, Property Condition Disclosure Act amended.

Is the house in FEMA's flood zone?

The map shows whether the address sits inside FEMA's high-risk flood zone, or within 30 m of its edge. Inside it, a government-backed mortgage comes with a requirement to buy flood insurance.

It does not show water from a burst pipe, a backed-up drain or groundwater, which can reach a house anywhere. Almost one-third of federal flood insurance claims from 2014 to 2024 came from outside high-risk areas (FloodSmart).

Ask the seller whether the house has had a flood claim, and your lender whether it will require flood insurance. Our flood zone guide has each area's share and its ZIP's claims since 1978.

How high is the ground?

The map shows the ground height around the house, from a 10 m elevation grid, and how it compares with the rest of the area and the county.

It does not show the height of the floor, the basement or the doorways. Those decide where water stops, and only a survey measures them.

Ask whether the seller has an elevation certificate. An elevation certificate records the building's floor heights.

How close is the groundwater?

The map shows how far below the surface groundwater was mapped at the address in a spring 2013 survey. Within about 14 ft it is within reach of a basement floor; within about 16 ft, of a cesspool ring.

It does not show how the water table moves from season to season or year to year. It is one survey, not a forecast.

Ask whether the basement has ever taken water, whether there is a sump pump and how often it runs. Ask the inspector to look for water lines, stains and efflorescence on the basement walls.

Sewer or cesspool?

The map shows whether a county sewer main is mapped past the address.

It does not show whether the house is connected to it, or systems that towns and villages run themselves, which the county layer leaves out. That matters most in Brentwood, Huntington, Patchogue, Riverhead and Westhampton Beach, where the county layer maps far fewer addresses on a main than are sewered.

Ask whether the house is on the sewer or on a cesspool or septic system, and if it is not on the sewer, when the system was last pumped and whether it has been replaced. Our cesspool guide has the count for each area, and the cesspool overflow page the county's replacement rules.

Storm surge and evacuation zones

The map shows whether the address is in one of the county’s storm-surge zones, and its hurricane evacuation zone letter.

It does not show what any one storm will do. The zones are drawn from storm models, not from past floods.

Ask the seller what happened at the house in past hurricanes and nor’easters.

The house itself

The 2025 county tax roll shows the year built, the living area and the assessor's use class, where it could be matched to the address.

It does not show renovations, and the roll can be wrong.

Ask the inspector about the age and material of the drain line from the house, and whether it has been camera-inspected.

More for Suffolk County

• Flood zones and flood insurance by area
• Cesspools by area: what the sewer map shows
• Check an address

Sources

• New York State Bar Association: Property Condition Disclosure Act amended (2024)
• FloodSmart (FEMA): What is my flood risk?