Real estate water testing is a lab panel ordered during escrow to check what a standard inspection cannot: the metals, nitrate, and other chemistry dissolved in a property’s water. In the South Bay, from San Jose to Sunnyvale, private wells and decades-old city plumbing both show up in transactions, and agents who raise it at the offer stage give buyers a result inside the standard contingency window instead of a question that surfaces after close.
What Does Real Estate Water Testing Actually Cover?
A real estate water test is a laboratory panel, not a line on the inspector’s checklist. It measures lead against the EPA’s action level, nitrate against the 10 mg/L limit, and a property’s broader metals and mineral profile.
A standard home inspection covers the water heater and visible plumbing; a water test covers what is actually in the water passing through it. Buyers on private wells have the strongest case for ordering one, since a well is an unmonitored water system changing hands along with the property:
- Well properties: an unmonitored system with no utility or regulator behind it
- City water, pre-1986 plumbing: lead and copper exposure between the main and the tap
- Properties near industry, agriculture, or military sites: added PFAS risk worth a broader panel
Buyers on city water with pre-1986 plumbing are close behind well owners, since lead and copper exposure happens inside the home’s own pipes, not the utility’s.
What Does California Law Require Sellers to Disclose About Water?
California’s Transfer Disclosure Statement, required under Civil Code Section 1102 for most residential sales, asks the seller to identify the water source as city or well and disclose known material problems with it. The statute does not require a water test, only disclosure of what the seller already knows.
An agent’s suggestion matters here. A seller who has never tested has nothing to disclose about water chemistry, because nobody measured it. A buyer’s own test, ordered during the contingency period, is the only way anyone in the transaction learns the actual numbers.
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Order a Water Test →When Do Lenders Require a Water Test in a South Bay Closing?
It depends on the loan program and the water source. FHA, VA, and USDA loans set conditional water-quality requirements for wells that conventional loans skip.
Under HUD Handbook 4000.1, FHA loans do not require automatic testing of an individual well unless state or local jurisdiction mandates it, contamination is suspected, a water treatment system addresses existing contaminants, or the lender asks for one; where a test is required, the local health authority’s standard applies, or the EPA’s maximum contaminant levels where no local standard exists. VA Pamphlet 26-7, Chapter 12 holds individual water supplies on VA loans to that same local-authority-or-EPA standard, collected by a disinterested third party rather than the buyer, seller, or agent. USDA-guaranteed loans on well-served properties generally call for a water test from a laboratory meeting the state’s testing standards, checked against EPA-based potability limits, including the 10 mg/L nitrate limit.
The numbers a lender’s water quality items report are the EPA’s nitrate limit of 10 mg/L, a nitrite limit of 1 mg/L, and a lead action level of 0.015 mg/L, dropping to 0.010 mg/L once the Lead and Copper Rule Improvements fully phase in on November 1, 2027. City-water buyers on conventional financing face no such requirement.
Does Santa Clara County Require Well Testing at Sale?
No. Santa Clara County’s Department of Environmental Health regulates new well construction and water-system clearance permits, but has no point-of-sale testing mandate for an existing private well changing ownership. That puts Santa Clara County in a different position than neighboring Santa Cruz County, which since September 2025 has required sellers on private wells to provide water quality and yield test results before closing.
Agents working both counties should not assume the rule travels across the county line. In Santa Clara County, a water test at closing happens because a lender requires it, a buyer requests it, or an agent suggests it.
Which Package Fits a Well or City-Water Property?
The property’s water source decides the panel. KELP’s Real Estate Well Water panel ($199) covers wells; city-water homes fit the Essential ($199) or Complete ($249) tiers.
Order the panel that matches what’s under the property:
- Private well, standard transaction: Real Estate Well Water ($199)
- City water, pre-1986 plumbing: Essential Home ($199)
- City water, full chemistry request: Complete Home ($249)
- Documented risk nearby (industrial, agricultural, military): Ultimate ($549 to $699), which adds a full PFAS panel to the metals and chemistry base
| Property situation | Recommended panel | Price | Coverage |
|---|---|---|---|
| Private well, standard transaction | KELP Real Estate Well Water | $199 | 10 metals (incl. lead), alkalinity, hardness, TDS, fluoride, nitrate, nitrite, sulfate, chloride |
| City water, pre-1986 plumbing | KELP Essential Home | $199 | Heavy metals (lead, arsenic, copper), hardness and minerals |
| City water, full chemistry request | KELP Complete Home | $249 | Adds aluminum, cadmium, mercury, fluoride, nitrates, bromides, phosphates |
| Near industrial, agricultural, or military sites | KELP Ultimate | $549 to $699 | Adds a full PFAS panel to metals and chemistry |
If the property is on a private well, the decision defaults to the $199 Real Estate Well Water panel. Our well water testing guide explains what each result means once the report is back; the Ultimate tier is worth raising only where a specific nearby risk exists.
Where Does Testing Fit Between Offer, Inspection, and Close?
California’s standard purchase agreement, C.A.R. Form RPA-CA, gives buyers 17 days after acceptance for inspections by default. KELP reports 5 to 7 business days after the lab receives the sample.
A South Bay closing moves through three stages once the offer is accepted:
- Offer accepted: order the panel the same day, since the clock on the contingency period is already running.
- Inspection contingency (17 days by default): the lab report typically lands with roughly ten days still open, alongside the general inspection and appraisal.
- Close: a dated lab result travels with the transaction file, useful to either side if a number needs a follow-up conversation.
Against a transaction that already carries an earnest money deposit, an appraisal, and a full inspection report, a $199 to $249 water panel is a small line item to raise and a fast one to clear. Whether the buyer or seller pays is negotiable like any other inspection cost; on well properties, some sellers test proactively so a documented result is already in hand when the first offer comes in.
This page covers the transaction timeline and package selection for agents and buyers; it does not cover the buyer’s own step-by-step testing walkthrough, which our home-purchase testing guide handles directly, or the mechanics of choosing a lab generally, covered in how to choose a water testing lab.
Frequently Asked Questions
Is water testing required to buy a house in California?
Not by state law. The Transfer Disclosure Statement requires sellers to identify the water source and disclose known problems, but neither the statute nor Santa Clara County requires an actual test. Some lender programs, including FHA, VA, and USDA loans on well properties, carry their own conditional testing requirements.
Who pays for water testing in a home sale?
It is negotiable like any other inspection cost. Buyers typically order and pay for it during their contingency period, and some well-property sellers test proactively so a result is already available when offers come in.
How long does real estate water testing take?
KELP reports 5 to 7 business days after the lab receives the sample. Ordered at offer acceptance, results typically land with about ten days remaining inside California’s standard 17-day contingency period.
What does a real estate water test cost?
KELP’s Real Estate Well Water panel is $199. City-water panels start at $199 for the Essential tier and $249 for the Complete tier, with a PFAS-inclusive Ultimate tier at $549 to $699 for properties with higher risk factors.
KETOS Environmental Lab Services
KETOS Environmental Lab Services (KELP)
520 Mercury Dr, Sunnyvale, CA 94085
(408) 357-4745
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Order a panel at kelp.ketos.co/order-form or call (408) 357-4745 for volume pricing.
Sources: California Civil Code Section 1102 (Transfer Disclosure Statement requirement); HUD Handbook 4000.1 / HOC Reference Guide on individual water systems; VA Pamphlet 26-7, Chapter 12; USDA Rural Development single-family water quality guidance; EPA National Primary Drinking Water Regulations (nitrate, nitrite, lead action level); C.A.R. Form RPA-CA Section 14(B)(1); Santa Clara County Department of Environmental Health well construction and water system clearance program; KETOS KELP panel specifications from ketos.co. All checked September 17, 2026.
