Total Chlorine
Free chlorine plus what has already reacted. On a chloraminated supply, this is the number that counts.
- Safe range
- 0 – 4 mg/L (US EPA maximum residual disinfectant level, which is a ceiling on how much disinfectant a system may deliver rather than a contaminant limit. There is no floor here: a private well is not required to carry a residual at all.)
- Measured in
- mg/L
What it is
Total chlorine is everything: the free chlorine still available to disinfect, plus the combined chlorine that has already bound to ammonia or organic matter. The difference between total and free is the combined fraction.
Why it matters
Which of the two numbers matters depends on how your utility disinfects. A system using free chlorine wants a free residual, and total chlorine tells you mostly how much has been used up. A system using CHLORAMINE — deliberately combining chlorine with ammonia for a longer-lasting residual — has almost no free chlorine by design, and total chlorine is the reading that describes its disinfection. Testing only free chlorine on a chloraminated supply produces a near-zero result that looks alarming and means nothing.
How to measure it
A strip or a drop kit reading total chlorine, at the tap. Find out first whether your utility uses chloramine, because that decides which number you should be looking at.
Test strips
- How trustworthy
- Dependable
- 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.
Most chlorine strips read free and total on separate pads. On a chloraminated supply the total pad is the one carrying the information.
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.
A DPD kit reads free chlorine first, then total after a second reagent. The difference between the two readings is the combined chlorine.
Where to find it: Pool shops and online. Reagents expire, so buy replacement bottles rather than a whole new kit each season.
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.
Tells you which disinfectant your system uses, which is the thing worth knowing before you interpret any chlorine reading 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.
- • Test immediately at the tap. Chlorine leaves water on standing and on agitation, so a sample carried across the house reads low.
- • Run the tap for a minute first unless you are deliberately testing the standing water in your own pipes.
Further reading: US EPA: National Primary Drinking Water Regulations, the enforceable health-based limits; US EPA: Consumer Confidence Reports, the annual report every community water system publishes
If it is too low
Little or no residual. Normal for a private well, which is not required to hold one; on a mains supply it may mean you are at the end of a long run, or that water has been standing in your plumbing.
- • Nothing, on a well. On mains water, run the tap for a minute and retest — a low reading often just means standing water.
If it is too high
Noticeable chlorine taste and smell. Above the regulated maximum it is worth reporting to the utility.
- • An activated carbon filter removes chlorine and chloramine, though chloramine needs a longer contact time and a filter rated for it.
- • A jug of water left in the fridge overnight loses free chlorine on its own. Chloramine does not, which is one practical difference between them.
- • Report a persistently high residual to the utility.
Common questions
Why is my free chlorine zero but total chlorine high?
Your utility almost certainly uses chloramine. It is chlorine deliberately combined with ammonia to give a residual that lasts further through the distribution network, and it registers as combined rather than free — so total is the reading that describes it and free is expected to be near zero.
Does boiling or standing remove chloramine?
Not the way it removes free chlorine. Free chlorine dissipates from a jug left overnight; chloramine is far more stable and largely stays. Activated carbon rated for chloramine, with enough contact time, is the reliable route.
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.