Silver
Rare in tap water, and usually traceable to a filter that was sold as antimicrobial.
- Safe range
- 0 – 0.1 mg/L (US EPA SECONDARY standard, set on permanent skin discolouration rather than on toxicity.)
- Measured in
- mg/L
What it is
Silver is not a common natural constituent of drinking water. Where it appears, it has usually been introduced: some filters and treatment devices use silver as a bacteriostatic agent to stop bacteria growing in the media, and a proportion of it washes out into the water.
Why it matters
The standard for silver is a secondary one, and the effect it guards against is argyria — a permanent blue-grey discolouration of the skin from long-term accumulation. It is cosmetic rather than dangerous, and it does not reverse. Silver is not regulated as a health-based contaminant in drinking water.
How to measure it
A laboratory metals panel. There is rarely any reason to test for it unless you run silver-treated filtration.
Certified laboratory, mail-in kit
- How trustworthy
- Reference grade
- Cost
- Most expensive
- Effort
- Careful sampling, then days or weeks of waiting
You are posted bottles and instructions, you fill them exactly as told, and you post them back. Weeks later a report arrives with figures nobody has to interpret by eye. This is what a result you intend to act on should be built from.
On comprehensive panels, absent from basic ones. Take samples before and after any filter you suspect — that comparison is the whole test.
Where to find it: State-certified drinking water laboratories; your state's certification officer keeps the list, and many public health departments will point you at one.
Your utility's annual water quality report
- How trustworthy
- Reference grade
- Cost
- Free
- Effort
- A few minutes of reading
Every community water system in the US has to publish one each year, free, listing what it found and what the limits are. It is real laboratory data about the water leaving the plant and travelling the mains. What it cannot describe is your own plumbing.
A secondary standard, so coverage varies and many systems do not report it at all.
Where to find it: Your water bill, your supplier's website, or the EPA's index of reports. It is also called a Consumer Confidence Report or CCR.
Taking the sample
For several of these the sample is where the error is, and no instrument recovers from a bad one.
- • Sample either side of the filter. Silver from a cartridge shows up on the outlet and not on the inlet, which identifies the source in one go.
Further reading: US EPA: Secondary Drinking Water Standards, the non-enforceable guidance on taste, odour and staining
If it is too low
Nothing to act on.
- • No action needed.
If it is too high
Long-term consumption at this level risks a permanent grey-blue skin discolouration. Check what treatment devices are in the line.
- • Look at your own filters first. A silver-impregnated cartridge is by far the most likely source.
- • Flush a new filter thoroughly before use; the initial output carries the most.
- • Reverse osmosis removes it if the source cannot be eliminated.
Common questions
Why is there silver in my filtered water?
Many filter cartridges are impregnated with silver to stop bacteria colonising the carbon between uses. Some of it washes out into the water, especially from a new cartridge, which is why a thorough initial flush is worth doing.
Is colloidal silver in water dangerous?
The documented consequence of long-term intake is argyria, a permanent blue-grey discolouration of the skin. It is disfiguring rather than toxic, and it does not fade once established.
WiseWaterGauge helps you record and understand your own readings. It is not a substitute for a certified laboratory test, and nothing here is medical or regulatory advice. If a health parameter is out of range, confirm it with an accredited lab and speak to your water provider.