Last checked: October 28, 2026

Lead in well water: first-draw vs flushed samples, and lead-certified filters

Lead in a private well system rarely comes from the groundwater itself. It usually comes from the pipes, solder, brass fittings and pump parts the water passes through, and more of it dissolves when water is corrosive or sits still. That's why health agencies ask for two samples, not one. Here's how to take them, what the comparison tells you, and what agencies say to do about it, with a source for every claim.

Why lead matters

CDC says no safe level of lead exposure has been identified for children, and even at low exposure levels children can show neurodevelopmental deficits.³ The Minnesota Department of Health (MDH) says there is no safe level of lead, recommends lead in water be as close to zero as possible, and says babies, children under 6 and pregnant women are at the highest risk.²

The federal Safe Drinking Water Act doesn't require monitoring of private wells, which is why CDC says testing them for lead is important.³ Lead usually doesn't change the water's taste, color or smell.¹

Where the lead comes from

Connecticut's Department of Public Health (CT DPH) says lead in private well systems is rarely found to come directly from groundwater; it's more likely from corrosion of lead-containing parts of the plumbing.¹ MDH says Minnesota groundwater usually doesn't contain detectable lead.² Sources both agencies list:¹²

• Lead pipes, most likely in homes built before 1930 (CT DPH). MDH calls lead pipes typically the worst contributor.
• Lead solder on copper pipes, possible in homes built before the end of 1986 (CT DPH).
• Brass and bronze parts: faucets, valves, fittings and check valves. Since January 4, 2014, federal law limits the wetted surfaces of pipes, fittings and fixtures for drinking water to 0.25% lead by weight; before that, "lead free" allowed up to 8%.
• Parts in the well itself: lead "packers" above the well screen (MDH says common in Minnesota wells drilled before 1980, and prohibited there in 1993) and some submersible pumps made before 1995 with leaded-brass parts.

Corrosive water makes it worse. CT DPH lists low pH, soft water, chloride over 250 mg/L, high dissolved oxygen, long standing time in the pipes, hot water, stray electrical current and dissimilar metals as factors. Signs can include blue-green stains on copper fixtures, pinhole leaks, visible pipe corrosion and a metallic or bitter taste.¹ CDC adds that particulate lead (bits of metal, especially from brass) is easy to miss with standard sampling; particles caught in faucet aerators have tested positive for lead.³

When to test

• At least once, say CT DPH and MDH.¹²
• Every 3–5 years when someone in the home is planning a pregnancy, there are children under 6, or the water is corrosive (CT DPH).¹
• When buying a home, if the lab panel doesn't already include lead. Some states put lead in the sale test: New Jersey's Private Well Testing Act list includes it, for example.⁵ See our homebuyer's guide.
• After new brass parts are installed: MDH says new brass can release lead especially in the first few months, and to flush before drinking.²

Use a state-certified laboratory and follow its sampling instructions; CT DPH says home lead test kits may not give accurate results.¹ CDC says to use your state's approved sampling protocol, or EPA's if your state doesn't have one.³

First-draw and flushed samples

CT DPH describes the two-sample method like this:¹

1. First draw. Let the water sit unused in the plumbing for at least 6 hours (overnight is typical). Without removing the aerator and without running the water first, fill the lab's bottle from the cold tap. This sample usually has the most lead, because it sat longest against the plumbing. Connecticut law defines a first-draw sample as one liter of tap water that has stood in the pipes at least six hours, collected without flushing.⁴
2. Flushed. Run the cold water for at least 3 minutes, then fill a second bottle. This shows the water that hasn't sat in the household plumbing.

MDH describes the same pair, with the flushed sample taken after running the water for a minute or two.² Follow your lab's exact instructions. CT DPH also suggests testing pH, alkalinity, hardness, sulfate and chloride, which affect corrosivity and help with treatment choices.¹

Reading the two results

Connecticut's action level for lead in private wells is 15 µg/L (micrograms per liter, the same as parts per billion).¹ CT DPH's guidance:¹

Compare the two samples. If the first draw is higher than the flushed sample and the flushed sample is at or under 15 µg/L, the lead is likely coming from the household plumbing, and CT DPH says you might consider running the cold tap at least a minute before using it for drinking or cooking.¹ MDH adds that the only way to know whether running the water lowered the lead is to test.² If the flushed sample is still high, MDH says to treat the water.² Use only cold water for drinking and cooking: CT DPH says never to use the hot tap for them, and MDH says to use cold water for drinking, food and baby formula.¹²

The 15 µg/L figure is Connecticut's. MDH doesn't set a number for well owners and says to keep lead as close to zero as possible.² Use your own state's guidance. See how to read your test results.

What to do about lead

CT DPH lists these steps, starting with the source:¹

• Remove the source: replace lead pipes, solder, fixtures, well pump parts or other components containing lead.
• Fix corrosive water (for example, low pH or very soft water) with treatment aimed at that cause.
• Eliminate stray electrical current in the plumbing, if found.
• Flush before drinking and cooking, if the two-sample comparison supports it.
• Point-of-use treatment for the tap you drink and cook from.
• Bottled water as an alternative. CDC says to choose bottled water certified by an independent testing organization, and notes it may not be the most cost-effective long-term option.³

Lead-certified filters

CT DPH and MDH list reverse osmosis, distillation, and activated carbon filters certified or designed to reduce lead, usually installed at a single drinking-water tap.¹² CT DPH says to verify with the vendor or manufacturer that a unit reduces lead before you buy it.¹

For faucet, refrigerator, pitcher and bottle filters, EPA's consumer tool says to look for:⁶

• a certification mark from an ANSI-accredited third-party certifier (EPA's tool names NSF, WQA, IAPMO R&T, UL Solutions and CSA, each with a product listing directory);
• a statement that the filter is tested against NSF/ANSI Standard 53 with a claim of lead reduction (EPA's tool describes certification to reduce lead to 5 ppb or less);
• ideally also NSF/ANSI Standard 42 for particulate reduction (Class I).

Check the certifier's directory for the exact model and replacement cartridge, and replace cartridges on schedule. A filter treats the water; it doesn't remove the lead source, so retest after any change. See whole-house vs. point-of-use treatment.

Where to get tested and treatment options

Related guides

• Free tool: Well Test Results Checker: type in your lab numbers and see each one next to the EPA benchmark.
• How to read your well water test results
• How often to test a private well
• Private wells in Connecticut: the state's lead action level and DPH's recommended tests