Yes, run the tap when water has sat in your pipes for a few hours, but how long matters. If your home has no lead service line (the pipe from the street to your house), run the cold tap for 30 seconds to 2 minutes, or until it turns cold and stays cold. If it has one, or you don't know, run it for at least 5 minutes, or use at least that much water some other way first, such as a shower or a load of laundry.
A quick rinse can backfire. In a 2018 study of 376 New Orleans homes, lead went slightly up after a 30-second flush and didn't drop significantly until the 6-minute mark.
:::takeaway ✅ The short version:
- Flush after water has sat for a few hours: first thing in the morning and when you get home from work.
- No lead service line: 30 seconds to 2 minutes, or until cold. Lead line or not sure: at least 5 minutes.
- A shower, laundry or dishwasher load counts if it runs before you fill your glass. Then run the kitchen tap briefly.
- Cold water only for drinking, cooking and baby formula. Boiling doesn't remove lead.
- Flushing lowers lead; it doesn't remove it. With a lead line, a baby or a pregnancy at home, use a filter certified to NSF/ANSI 53 for lead. :::
How long should you run tap water before drinking?
It depends on one question: is the pipe from the street to your house made of lead?
| Your home | How long to run the cold tap |
|---|---|
| No lead service line | 30 seconds to 2 minutes, or until it turns cold and stays cold |
| Lead service line, or you don't know | At least 5 minutes, or the same amount of water used some other way first. Longer if the line is long or the house sat empty |
| Any home, after plumbing work or a lead line replacement | Follow your utility's longer flushing instructions |
Your utility's number beats any national one. EPA says the time "will depend on whether your home has a lead service line or not, and the length of the lead service line."
Federal advice used to give a number. Until late 2024, the standard lead statement for utilities' annual water quality reports said to flush "for 30 seconds to 2 minutes." It now says to "flush your pipes for several minutes." EPA's consumer page now gives no time and says to ask your utility.
Utilities still differ:
| Who | What they tell customers |
|---|---|
| New York City DEP | "At least 30 seconds, until the water gets noticeably colder" |
| DC Water | Until you notice a temperature change, "then run for an additional two minutes" |
| Michigan EGLE (statewide) | No lead line: 30 seconds to 2 minutes, or until cold. Lead line: "at least five minutes" |
| Chicago | After 6 hours or more unused, "at least 5 minutes" |
| Denver Water | After a few hours unused, "five minutes" |
The table at the top of this section follows Michigan's split.
Why does water that sat overnight have more lead?
Lead gets into tap water when plumbing that contains lead corrodes, and time is one of the factors EPA lists: "The more time water has been sitting in pipes, the more lead it may contain."
The three usual sources:
- Lead service lines, the pipe that runs underground from the water main to your house. Where one exists, EPA calls it "typically the most significant source of lead in the water." EPA's latest estimate is about 4 million still in use across the country.
- Lead solder on copper pipes, banned in 1986.
- Brass faucets and fittings. Until 2014, plumbing sold as "lead free" could contain up to 8% lead. It's now limited to a weighted average of 0.25%.
It isn't only overnight. In an EPA lab setup built with an old lead service line, lead in the line reached about 55% of its eventual level within 2 hours of the water sitting still, and leveled off after roughly 7 to 18 hours. So water that sat during a workday counts too.
Is the first glass of water the worst for lead?
In a home with a lead service line, usually not. Water comes out of your tap in the order it sat. The first liter or so, sometimes several, sat in your faucet and indoor pipes. Next comes the water that sat in the service line. Then fresh water from the main.
Official lead tests use the first liter out of the tap after water has sat, called the first draw. When researchers sampled 32 Chicago homes with lead service lines liter by liter, "lead levels measured with sequential sampling were highest within the lead service lines, with maximum values more than four times higher than Chicago's regulatory compliance results using a first-draw sampling protocol." EPA scientists who tested homes in Flint found the service-line water arriving after about 2 liters in one home and about 4 liters in another, and lasting to about the 7- and 10-liter marks.
The first glass isn't always innocent, though. In one Flint home, in one sampling round, the highest samples, up to 87 µg/L (87 parts per billion, or ppb), came in the first 2.25 liters. The researchers judged a brass fixture next to the faucet the most likely source of the first of those peaks.
This is why the 2024 Lead and Copper Rule Improvements require utilities, starting November 1, 2027, to collect both the first and the fifth liter at homes with lead lines and use the higher result.
Why a 30-second rinse can make lead worse
In a lead-line home, a short rinse clears the faucet and can pull the service-line water forward just as you fill your glass. A New Orleans study sampled 376 homes at the first draw and again after about 30 seconds, 3 minutes and 6 minutes of running, though it couldn't tell which homes had lead service lines: residents and the utility mostly didn't know, and only 38 of the 376 had a confirmed or reported lead line.
Even after 6 minutes, 52% of samples still had detectable lead (1 ppb or more). The authors concluded that common flushing advice is "an inconsistently effective exposure prevention measure that may inadvertently increase exposures."
Median lead was low at every step, 1.1 to 1.7 ppb. The trouble is stopping too soon. The authors offer two reasons for the 30-second rise: 30 to 45 seconds is often just long enough to bring the water that sat in the service line up to the tap, and flushing may have knocked loose lead particles.
Does "run it until it's cold" work?
Only if you don't have a lead service line. Cold water is supposed to mean fresh water from outside the house. But the service line is buried too, so the water that sat in it can already feel cold, and the tap can turn cold just as it arrives.
So the advice splits. Michigan accepts "until it becomes cold or reaches a steady temperature" only for homes without a lead line. DC Water tells customers to run the tap until the temperature changes and then for two more minutes.
How do I know if I have lead pipes?
- Ask your water utility. Every utility had to file an inventory of its service line materials by October 16, 2024, and the rule requires it to be public. Those serving more than 50,000 people must post it online. Searching your utility's name plus "service line inventory" usually finds it. Ask whether your line is lead, galvanized steel or unknown.
- Check the pipe yourself. Find where the water line comes into your house, usually near the meter or main shutoff. EPA's Protect Your Tap guide walks you through it: "All you need is a penny (or key) and a magnet." If the pipe is gray, scratches easily and a magnet won't stick to it, EPA says it may be lead. Lead Safe Chicago adds that lead "will show a silver scratch mark."
- Check when the house was built. EPA notes that lead pipes "are more likely to be found in older cities and homes built before 1986."
If you can't tell, treat it as lead until you know. That means the 5-minute flush.
Does a shower or laundry count as flushing?
Yes. EPA's advice is to "flush your home's pipes by running the tap, taking a shower, doing laundry, or doing a load of dishes." Chicago and DC Water say the same.
But:
- It has to happen before you fill your glass. A shower after your coffee doesn't help the coffee.
- Still run the kitchen tap briefly. Minneapolis notes that "you'll still need to flush individual faucets for a short time before using them for drinking water." A shower doesn't move the water sitting in the pipe to your kitchen sink.
How much water and money does flushing use?
Federal rules (10 CFR 430.32) cap kitchen and bathroom faucets made since 1994 at 2.2 gallons per minute at 60 psi. Many run slower, so for most homes these are upper limits:
| Daily flush | Water per year | Cost per year |
|---|---|---|
| 1 minute | about 800 gallons | about $7 to $22 |
| 2 minutes | about 1,600 gallons | about $15 to $43 |
| 5 minutes | about 4,000 gallons | about $37 to $109 |
The low end is a rough national price from EPA WaterSense figures (about $9 per 1,000 gallons). The high end uses DC Water's FY2027 rates for water, sewer and the per-gallon city fees on the bill, about $27 per 1,000 gallons. Your bill shows your own rate. A one-minute daily flush is less than 1% of the water an average family uses.
To waste less:
- Catch it for houseplants or cleaning, but not the vegetable garden: Philadelphia's water department lists watering vegetable gardens among the uses that should get fresh, flushed water.
- Fill a pitcher after you flush and keep it in the fridge for drinking and cooking that day.
- More in our guide to conserving water at home.
Does running water remove lead?
It lowers lead, but it doesn't remove it. Lead starts building again as soon as the water stops moving, and the 2024 lead rule notes that "lead particulates can be released sporadically or as a result of service line disturbances even in systems that have well-operated" corrosion control.
EPA's health goal for lead in drinking water is zero, and the CDC says "no safe blood lead level (BLL) in children has been identified." EPA estimates that infants who mostly drink formula mixed with tap water can get 40% to 60% of their lead exposure from water.
So if you have a lead service line, a baby on formula, or someone pregnant at home, add a filter. (The CDC's filter advice isn't limited to those homes; it covers anyone concerned about lead in their water.) What to look for:
- The CDC says to look for certification to NSF/ANSI 53 for lead and NSF/ANSI 42 for particles.
- EPA's consumer guide says to check that the filter is certified to reduce lead to 5 ppb or less. NSF/ANSI 53's lead limit dropped from 10 ppb to 5 ppb at the end of 2019, so a filter certified before then may only claim 10 ppb. Check the performance data sheet for the 5 ppb claim.
- In a Flint field study, "over 97% of filtered water samples contained lead below 0.5 µg/L" with faucet-mounted filters.
- Don't run hot water through the filter.
Compare water filters certified to reduce lead. The permanent fix is replacing the lead line. Under the 2024 rule, utilities have 10 years, starting November 1, 2027, to replace the lead service lines they control, with limited extensions. Where the law requires the owner's consent and the utility can't get it after a reasonable effort, it doesn't have to replace that line, but it must ask again if the home is sold.
Can I use hot tap water or boil it?
No to both, for drinking and cooking. The CDC says: "Water that comes out of the tap warm or hot can have higher levels of lead. Boiling this water will not reduce the amount of lead in your water." The federal rule specifically warns against using hot tap water for baby formula. More in our guide to what boiling does and doesn't do.
Showering and bathing are fine. EPA says "Human skin does not absorb lead in water."
My water system passed its lead test. Do I still need to flush?
Yes, if your home has lead plumbing. We looked at the latest EPA lead-and-copper results for the roughly 21,000 public water systems TapWaterData tracks that have a current result, one result per system (EPA data as of July 2026). The "action level" is the lead level that, if a system's result goes above it, requires the utility to take extra steps:
| EPA 90th-percentile lead result | Share of systems |
|---|---|
| Above 15 ppb (current action level) | 0.84% (175 systems) |
| Above 10 ppb (action level from November 2027) | 2.3% |
| Above 5 ppb | 8.6% |
Most systems pass. But a system's result is a high-end figure (the 90th percentile) from first-draw samples at a small set of homes the utility picks, which the rule says should be its highest-risk homes. The highest of those samples can be above the reported number. Until 2027 only the first liter is tested, which can miss the water that sat in a lead service line. Lead comes mostly from the service line and plumbing at each home, so a passing system can still have houses with high lead. Look up your system's result on our lead map, then use the steps above for your own tap. To know the lead level at your own tap, have it tested by a certified water testing lab.
Sources
- Katner A et al. "Effectiveness of Prevailing Flush Guidelines to Prevent Exposure to Lead in Tap Water." Int J Environ Res Public Health 15(7):1537, 2018.
- Del Toral MA, Porter A, Schock MR. "Detection and Evaluation of Elevated Lead Release from Service Lines: A Field Study." Environ Sci Technol 47(16):9300–9307, 2013.
- Lytle DA et al. "Sequential drinking water sampling as a tool for evaluating lead in Flint, Michigan." Water Research 157:40–54, 2019.
- Lytle DA et al. "The impact of sampling approach and daily water usage on lead levels measured at the tap." Water Research 197:117071, 2021.
- Bosscher V et al. "POU water filters effectively reduce lead in drinking water: a demonstration field study in Flint, Michigan." J Environ Sci Health A 54(5):484–493, 2019.
- US EPA. Basic Information about Lead in Drinking Water (updated June 18, 2026); Lead Service Lines; Fact Sheet: 2025 Update to the 7th DWINSA (November 2025); Consumer Tool for Identifying Point-of-Use and Pitcher Filters Certified to Reduce Lead (June 2024); Protect Your Tap; WaterSense Statistics and Facts.
- 40 CFR 141.80, 141.84, 141.85, 141.86, 141.152 and 141.154 (eCFR, current and 2020 versions); Lead and Copper Rule Improvements, 89 FR 86418 (October 30, 2024); 10 CFR 430.32.
- CDC. About Lead; Lead in Drinking Water.
- NSF. Stricter requirements for lead reduction certification (February 6, 2020).
- New York City DEP; DC Water; Michigan EGLE; Chicago Department of Water Management and Lead Safe Chicago; Denver Water; City of Minneapolis; Philadelphia Water Department.
- TapWaterData analysis of EPA SDWIS lead-and-copper 90th-percentile results (download as of July 9, 2026).
