Buying land in the Phoenix area: water, lot splits and due diligence

Water and land-division law is technical, so have a land-use attorney or an engineer review a specific parcel.

Water comes first

Most of the Phoenix area is in the Phoenix Active Management Area (AMA), where Arizona’s assured water supply rules apply. Under A.R.S. § 45-576, anyone offering subdivided land for sale in an AMA must show a 100-year assured water supply: either a certificate of assured water supply from the Arizona Department of Water Resources (ADWR), or a written commitment of service from a water provider ADWR has designated as having one. A city, town or county can approve a subdivision plat only with one of the two.

In June 2023, ADWR’s model of the Phoenix AMA projected 4.86 million acre-feet of unmet groundwater demand over 100 years. As a result, ADWR says the State won’t approve new assured water supply determinations in the Phoenix AMA based on groundwater, and new determinations must rely on other water sources. It says its 2024 update doesn’t support groundwater-based determinations. It published a further model update in 2026, and its page doesn’t say whether that changes this position, so ask ADWR where it stands. ADWR says existing homeowners are protected and that development within existing certificates or designations may continue. A separate rule adopted in November 2024 gives some water providers in the Phoenix and Pinal AMAs an alternative route to a designation. Ask ADWR or the provider whether it applies, and its current status.

What to confirm for a parcel:

• Who will serve water: a city, a private water company, or a well. Ask the provider in writing whether it will serve the parcel, and on what terms.
• Whether a designated provider serves it, or whether an existing certificate covers it.
• For a well: its status, registration and water quality, and whether the parcel is in a water rights adjudication. The seller’s affidavit of disclosure, where required, asks about these.

Lot splits and subdivisions

How a parcel was created matters as much as its size.

• Under the State’s real estate law (A.R.S. § 32-2101), dividing land into six or more lots of less than 36 acres each for sale or lease is a subdivision. Unless an exemption applies, it needs a public report from the Arizona Department of Real Estate and, in an AMA, an assured water supply (A.R.S. § 32-2183). Lots of 36 acres or more can still fall under the separate rules for unsubdivided land.
• In unincorporated county areas, A.R.S. § 11-831 lets counties review splits of five or fewer lots, any of them 10 acres or smaller, mainly for zoning, legal access, physical access and utility easements. Dividing into six or more through a series of splits “in concert” to avoid the subdivision laws is unlawful.
• Within a city or town, A.R.S. § 9-463.02 treats a division into four or more lots as a subdivision, so a city’s rules can apply sooner than the county’s. Check the city or town’s own land-division rules.

A parcel created by an improper split can have trouble getting building permits. Ask how and when the parcel was created, and check the recorded documents.

The affidavit of disclosure (A.R.S. § 33-422)

When a seller sells five or fewer parcels, other than subdivided land, in an unincorporated area of a county, the seller must give the buyer a completed affidavit of disclosure at least seven days before the transfer, and the buyer may rescind the sale for five days after receiving it. The seller records it with the deed. It covers, among other things:

• legal and physical access, and who maintains the roads;
• whether any part of the parcel is in a FEMA floodplain;
• soil conditions such as fissures or expansive soils;
• which utilities serve it, and the water source and provider;
• any on-site wastewater (septic) system and its inspection status;
• any solar or battery storage devices, and whether they’re leased or owned;
• whether it meets county zoning and land-division rules;
• whether it’s near a military installation or in its flight areas;
• any limits on its use from title encumbrances.

Inside a city or town the statute doesn’t apply, so ask the same questions yourself.

Septic and sewer

If no public sewer reaches the parcel, ask Maricopa County Environmental Services what a septic (on-site wastewater) system for the planned home would require. For an existing system, Arizona rules require an inspection within six months before ownership transfers, and in Maricopa County the buyer files a notice of transfer within 15 days after closing. Where a sewer line is nearby, ask the city what connecting would cost.

Zoning, hillside and desert rules

• City of Scottsdale: about two-thirds of the City is under the Environmentally Sensitive Lands Ordinance, which can require parts of a lot to remain natural as Natural Area Open Space (NAOS). That affects where and how much you can build, especially in the north.
• Town of Paradise Valley: the Town’s Resident Guide (revised 2023) says most of the Town is zoned R-43, with a minimum lot equal to 43,560 square feet, so confirm the current minimum for a parcel with the Town. Hillside lots need the Hillside Building Committee’s approval before a building permit, covering grading, lighting, walls and landscaping.
• Everywhere: check the zoning district, setbacks, height limits and any recorded CC&Rs or easements on the title commitment.

Before you commit

• Make the purchase contingent on the water, access, zoning and septic answers you need, with enough time to get them.
• Order a survey if the boundaries, access or easements are unclear.
• Get the title commitment and read every Schedule B exception.

The North Scottsdale and Paradise Valley pages describe the lots and homes there. To talk through a parcel, book a consultation, and see postal city vs. city limits for which town’s rules apply.