Chlorine
The disinfectant your utility adds to keep water safe all the way to your tap.
- Safe range
- 0.2 – 4 mg/L
- Ideal range
- 0.5 – 1.5 mg/L
- Measured in
- mg/L
What it is
Municipal suppliers add chlorine (or chloramine) to kill pathogens and to maintain a residual, a small amount that persists through the distribution network so water is still protected when it reaches you. Finding chlorine in tap water is a sign the system is working as designed.
Why it matters
Chlorine in drinking water is a genuine trade-off, and it is worth stating plainly which way it falls. Disinfection prevents waterborne disease outbreaks that used to kill people routinely. The cost is taste, odour, and trace disinfection byproducts. The benefit vastly outweighs the cost, which is why the answer to disliking the taste is a filter at the tap, not an unchlorinated supply.
How to measure it
A DPD test, the same chemistry pools use, in a version scaled for tap water. Before buying one, check the annual report for whether your utility uses chlorine or chloramine: a free chlorine test reads almost nothing on properly treated chloraminated water.
Test strips
- How trustworthy
- Ballpark
- Cost
- Low cost
- Effort
- Under a minute, wherever you drew the sample
A plastic strip with reagent pads on it. Dip it, hold it level, and match each pad against the chart on the bottle at the time the label tells you to. Most strips read several parameters at once.
Free and total chlorine strips for drinking water read a far lower scale than pool strips, which is exactly what makes them useful here.
Watch out: A pool strip barely registers tap levels, so a pool kit in the cupboard will tell you there is no chlorine in water that is properly disinfected. Buy strips sold for drinking water.
Where to find it: Pool shops, hardware stores, supermarkets and online, sold both per parameter and as multi-packs. Buy strips made for your kind of water: pool strips and drinking water strips read very different scales for the same chemistry.
Liquid reagent kit, colour match
- How trustworthy
- Dependable
- Cost
- Low cost
- Effort
- A couple of minutes, at a sink or poolside
A measured sample in a plastic comparator block, a few drops of reagent, and a colour you match against printed standards beside the tube. The two-tube kit sold everywhere for pools is this.
The same DPD reagent read against a comparator, at a scale suited to tap water. Buy one that reports free and total separately: the gap between them is the interesting part.
Where to find it: Pool shops and online. Reagents expire, so buy replacement bottles rather than a whole new kit each season.
Digital photometer
- How trustworthy
- Dependable
- Cost
- Most expensive
- Effort
- A few minutes per parameter
The same reagents as a drop kit, read by an instrument instead of your eye. It removes the colour judgement and gives a repeatable number, which matters most for people who are colour blind or testing in poor light.
Worth it only if you are testing regularly, for instance while commissioning a filter and wanting to know what it removes.
Where to find it: Pool trade suppliers and water-testing suppliers online. Reagent tablets or sachets are an ongoing cost.
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.
States the average and range of chlorine the system distributes, and which disinfectant it uses. That last detail is what decides which test to buy.
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.
- • Test the moment the sample is drawn. Chlorine leaves as water stands, warms and is stirred, which is the same reason a jug left in the fridge tastes better.
- • If you want to know what a filter is doing, take one sample at the tap and one after the filter within a minute of each other, and use the same test on both.
Further reading: US EPA: Consumer Confidence Reports, the annual report every community water system publishes
If it is too low
Little or no residual disinfectant. On a municipal supply this can indicate a distribution problem worth reporting. Private wells normally show zero and that is expected.
- • On a municipal supply, a persistent zero is worth raising with your provider.
- • On a private well, zero is normal, but wells are not disinfected at all, so bacterial testing matters more.
If it is too high
Strong chemical taste and smell, and can dry skin and hair. Usually harmless but unpleasant; often higher if you live close to the treatment works.
- • An activated carbon filter (pitcher, tap-mounted or under-sink) removes chlorine taste effectively.
- • Letting water stand uncovered for a while lets some chlorine dissipate; this does not work for chloramine.
Common questions
Is chlorine in tap water safe to drink?
Yes, at the levels used in public supplies. The US EPA sets a maximum residual disinfectant level of 4.0 mg/L, and typical tap water runs well below that. The public health benefit of disinfection is very large and well established.
How do I get rid of the chlorine taste?
Activated carbon filtration is the simplest and most effective option. If your utility uses chloramine rather than free chlorine, check that your filter specifically states chloramine reduction; many basic carbon filters are much less effective against it.
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.