Guide
Lead in older buildings: testing and filter options
Why lead is a plumbing problem rather than a supply problem, how to test properly, and which filters are certified for it.
Lead comes from the pipe, not the plant
Water leaving a treatment plant is essentially lead free. Lead dissolves into it on the journey to your tap, out of a lead service line, out of solder at pipe joints in buildings plumbed before 1986, and out of brass fittings and older fixtures.
This is why two neighbours on the same main can have very different results, and why a clean system-wide figure in a utility report tells you little about your own kitchen.
It is also why utilities work so hard on corrosion control. The treatment goal is to stop the water dissolving the pipes it travels through, which is a different objective from removing something at the plant.
Finding out where you stand
Start with the municipal service line inventory. Systems are now required to identify the material of every service line and publish the result, and many have searchable maps. An entry of lead or unknown is the trigger to test. Unknown is not reassuring, it simply means nobody has confirmed it.
Then test the tap. Only a certified laboratory analysis will do, because there is no reliable home test at the concentrations that matter. Many utilities supply free kits.
Follow the sampling instructions exactly, because how the sample is drawn changes the result more than almost anything else. A first-draw sample after water has stood in the pipes for several hours is the standard method, since standing water has had the longest contact with lead surfaces.
Build date is a reasonable proxy in the meantime. Anything plumbed before 1986 may have lead solder even where the service line is copper.
Filters that are actually certified for lead
The standard to look for is NSF/ANSI 53, certified specifically for lead reduction. Reverse osmosis systems certified under NSF/ANSI 58 also cover it.
A filter certified only under NSF/ANSI 42 has been tested for taste and odour. It has not been tested for lead, and the two products can look identical on a shelf.
Point of use beats point of entry here, and this is the case where intuition most often misleads. A filter at the main line sits upstream of nearly all the pipework that contributes lead. A certified filter at the kitchen tap sits downstream of all of it, and costs a fraction as much.
These filters are certified for cold water only. Hot water dissolves lead more readily and degrades the media.
Habits that matter as much as equipment
Run the cold tap until the water turns noticeably colder before drinking or cooking, particularly first thing in the morning. That clears water that has been standing against pipe surfaces overnight.
Never use hot tap water for drinking, cooking, or infant formula in a building with lead plumbing, filtered or not. Draw cold and heat it.
Clean tap aerator screens periodically, since lead particles can collect there.
Replace cartridges on rated capacity rather than on appearance. Lead breakthrough gives no taste or smell warning at all.
Replacement is the permanent answer
A filter protects one tap. The service line stays in the ground, and the bathroom tap a child drinks from is untouched unless it has its own filter.
Many municipalities now run service line replacement programmes, some at no cost to the owner, driven by federal requirements to remove lead lines. Check whether your address is on a list and get on it if so.
Immediately after a replacement, disturbed sediment can raise lead temporarily. Keep the filter in place and flush thoroughly for whatever period your utility recommends, because the weeks after the work are a genuine short-term risk.
Common questions
My building is from the 1920s. Is the water definitely unsafe?
No, and testing is the only way to know. Many older buildings have had service lines and internal plumbing replaced over the decades, and utility corrosion control substantially reduces how much lead dissolves even where lead pipe remains. Age raises the priority of testing rather than settling the answer.
Does boiling remove lead?
No. It concentrates it, because water evaporates and the lead stays behind. Boiling is the correct response to a microbiological boil-water notice and the wrong response to lead, nitrate, or PFAS.
I rent. What can I do without the landlord's permission?
A faucet-mount or countertop filter certified under NSF/ANSI 53 for lead needs no modification to the property and no permission. It is a reasonable answer while you raise the plumbing question. Testing is also worth doing, and in many jurisdictions a tenant can request information about the service line material for the building.
Related reading
- water problems: lead
- water filters: lead reduction
- water filters for: brownstones and pre war buildings
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