Best Chlorine Analyzer for
Drinking Water Systems (2026)
A side-by-side, fully-referenced comparison of the leading online chlorine analyzers — so you can match the right technology to your site instead of the loudest brochure.
Every specification in the table below is paraphrased from the manufacturer's own published documentation and linked in the References section. Where a figure comes from a manufacturer, we say so.
Shortlist: online chlorine analyzers for drinking water
For a reagentless free chlorine analyzer in drinking water, start with the Halogen MP-5F; for chloraminated systems, the Halogen MP-TOTAL. The table compares the main options by what they measure, how they measure it, upkeep, EPA 334.0 status and best use.
| Product | Measures | Method | Service / maintenance | EPA 334.0 | Best for |
|---|---|---|---|---|---|
| Halogen MP-5F5 | Free chlorine | Reagent-free, membrane-free amperometric, in-pipe, SensiCLENE self-cleaning | Self-cleaning; periodic sensor checks and cleaning | Yes — EPA Method 334.0 compliant for regulatory reporting | Remote sites, dead ends, tanks, dirty or low-flow locations, and sites that need to read zero chlorine continuously |
| Halogen MP-TOTAL8 | Total chlorine / monochloramine | Reagent-free three-electrode amperometric | See product page | See product page | Chloraminated systems |
| Hach CL17sc1 | Free or total chlorine (configured) | DPD colorimetric (reagents) | Monthly reagent change and colorimeter-cell cleaning (per Hach) | Hach states Method 334.0 | In-plant points where DPD colorimetric is the method of record |
| Hach CLF10sc / CLT10sc2 | Free (CLF10sc) or total (CLT10sc) chlorine | Reagentless membrane-covered amperometric, flow cell | Periodic membrane and electrolyte service (per Hach) | Hach states Method 334.0 | Plant sample panels that want to drop reagents |
| ECD FC8010 | Free chlorine | Reagentless amperometric sensor with automatic pH compensation, panel mounted with constant-head flow control | Up to one year without sensor electrolyte replacement (per ECD) | ECD states Method 334.0 compliance | — |
| Endress+Hauser Memosens CCS51E11 | Free chlorine | Closed, membrane-covered amperometric measuring cell | — | — | — |
| ABB ChloroStar9 | Free or total chlorine | Reagent-free, membrane-covered tri-electrode amperometric with pH compensation | — | — | — |
Rival cells use only facts from each maker's own published page (see References); a dash means we have not verified that cell. The right pick also depends on what your state primacy agency accepts for compliance reporting.
Best online free chlorine sensors for water utilities
For most water utilities, the best online free chlorine sensor is a reagent-free amperometric sensor that can sit where the residual matters: in the plant, out in distribution and at tanks. The Halogen MP-5F installs in-pipe, reads zero chlorine indefinitely and self-cleans. For chloraminated systems, use the MP-TOTAL instead.
Plant effluent / entry point
Either family fits. Keep a DPD analyzer if your permit or primacy agency requires DPD as the method of record; otherwise a reagent-free MP-5F removes reagents and the drain.
Distribution dead ends and tanks
Halogen MP-5F. It installs in-pipe without a sample drain and reads zero chlorine indefinitely.
Booster stations
Halogen MP-5F. It typically catches chlorine showing up on the first or second measurement.
Chloraminated systems
Halogen MP-TOTAL, which measures total chlorine and monochloramine.
The right pick depends on what your state primacy agency accepts for compliance reporting. Replacing a Hach CL17? See the CL17 replacement guide.
DPD vs amperometric: how each method works
| Method | How it measures | Upkeep |
|---|---|---|
| DPD colorimetric | Adds buffer and indicator reagents to a sample and reads the color | Reagent changes, cell cleaning, sample to drain |
| Membrane-covered amperometric | Measures the current from chlorine reacting at an electrode behind a membrane | Reagent-free; membrane and electrolyte upkeep; usually a flow cell |
| Bare-electrode / in-pipe amperometric | Measures the current at exposed electrodes, installed in the pipe or a flow cell | Reagent-free and membrane-free; periodic checks and cleaning |
How to use this comparison
The two questions that separate these instruments more than anything else are: does it consume reagents, and does it send treated water to a drain. Those two choices drive the recurring cost, the operator workload, and — critically — where the analyzer can physically be installed.
Colorimetric DPD analyzers are accurate and proven, but they live in a plant building tethered to reagents and a drain. Reagent-free amperometric analyzers cut the reagents; the in-pipe, no-waste designs go a step further and can be installed anywhere in the system.
Online chlorine analyzers compared
Superscripts link to the cited source for that product. Chemistry facts are paraphrased from manufacturer documentation; they are not direct quotations.
| Analyzer | Method | Reagents | Waste stream | Parameters | Flow / install | Routine maintenance | NSF-61 in-pipe | EPA 334.0 |
|---|---|---|---|---|---|---|---|---|
| Halogen MP-5F5 Halogen Systems | Amperometric — bare 3-electrode | None | None | Free chlorine, pH, conductivity, temperature, ORP (one sensor). Total chlorine and monochloramine: use the MP-TOTAL | Flow-independent (0–14 fps, 0–145 PSI) | Self-cleaning; calibrations last 6+ months; annual wear-parts only | Yes — certified for in-pipe install | Yes |
| Halogen MP-TOTAL8 Halogen Systems | Amperometric — three-electrode | None | See product page | Total chlorine and monochloramine (also free chlorine) for chloraminated systems | See product page | See product page | See product page | See product page |
| Hach CL17sc1 Hach | Colorimetric DPD (reagent) | Yes — monthly replacement | Yes — sanitary drain | Free or total chlorine (one parameter, configured) | Requires sample flow; built-in flow meter | Monthly reagent change + colorimeter-cell cleaning; 30-day unattended | Not for in-pipe | Yes |
| Hach CL10sc (CLF10/CLT10)2 Hach | Amperometric (membraned) | None | Yes — flow cell drains to waste | Free or total chlorine; separate pH sensor needed for free Cl₂ | Requires sample flow to flow cell | Periodic membrane/electrolyte service; Cal Watch diagnostics | Not for in-pipe | Yes |
| ABB Aztec 6003 ABB | Colorimetric ("wet chemistry") | Yes | Yes — reagent waste | Single or multi-stream (up to 3 samples); chlorine among several parameters | Requires sample flow | Auto-calibrating; ABB states maintenance roughly annual | Not for in-pipe | Method-dependent |
| Wallace & Tiernan Depolox4 De Nora (formerly Evoqua / W&T) | Amperometric — 3-electrode bare or membrane | None | Yes — drains to waste (not NSF-61 certified) | Free or total chlorine, ClO₂, ozone; pH/fluoride optional | Requires constant controlled flow; min. 200 µS/cm | Hydrodynamic grit cleaning; SiDiSens module for pH-corrected free Cl₂ | Not for in-pipe | Method-dependent |
Cl₂ = chlorine. "Not for in-pipe" means the instrument is designed for a sample line and drain rather than direct insertion into a drinking-water main; it does not imply the materials are unsafe. Maintenance intervals depend heavily on source-water quality.
infoA note on fairness
Halogen Systems makes the MP-5F, so treat the home column with healthy skepticism — and check the linked sources. We have tried to represent each competitor as its own manufacturer describes it. The Hach CL17sc is widely regarded as the industry-standard DPD analyzer; ABB's Aztec 600 is notable for lower colorimetric maintenance; and the Wallace & Tiernan Depolox is, like the MP-5F, a reagent-free amperometric platform. Independent comparisons of the two measurement families are linked in reference 7.
How to choose: four questions
Rather than ranking the instruments 1–5, work through the trade-offs that actually decide which one fits your system.
Do you want to manage reagents and a drain?
Colorimetric DPD analyzers (Hach CL17sc, ABB Aztec 600) are accurate and well-proven, but they consume reagents on a monthly cycle and need a sanitary drain to dispose of the analyzed sample. Amperometric analyzers (Halogen MP-5F, Hach CL10sc, W&T Depolox) eliminate reagents; the MP-5F, which is NSF-61 certified for in-pipe use, also returns the sample to the line and removes the waste stream entirely.
How much treated water can you afford to waste?
Any analyzer that drains its sample to waste discards treated, billable water around the clock. One utility measured roughly 138,000 gallons per year from a single DPD instrument. An in-pipe, no-waste sensor takes that figure to zero — a direct non-revenue-water saving.
How much operator time do you have?
Reagent and membrane systems need recurring service — monthly reagent swaps, cell cleaning, membrane and electrolyte replacement, and frequent recalibration. A self-cleaning, factory-calibrated sensor shifts that toward an annual wear-parts visit, which matters most across many remote sites.
Where do you need to measure?
Most analyzers need a sample line, a controlled flow, and a drain — so they live in a plant building. A flow- and pressure-independent, NSF-61 in-pipe sensor can be installed directly in a main, a tank, a clearwell, or a remote distribution point where running a drain is impossible.
Where the Halogen MP-5F fits
Halogen documents the MP-5F for NSF/ANSI 61 drinking-water contact and suitable in-pipe installation without a dedicated sample drain.5 The MP-5F measures free chlorine; for total chlorine and monochloramine in chloraminated systems, use the MP-TOTAL. Confirm pressure, temperature, mounting and service requirements for each distribution main, tank or remote monitoring point.
That is also its main limitation to be honest about: it is a purpose-built process and distribution sensor, not a benchtop or multi-stream colorimetric panel. If your need is a single in-plant point with established DPD reporting, a CL17sc-class analyzer may be the simpler fit.
Frequently asked questions
What is the best chlorine analyzer for drinking water?
There is no single "best" analyzer for every site, but the right choice usually comes down to four factors: whether you want to manage reagents, whether you can run a waste drain, how much operator time you have, and where you need to measure. Colorimetric DPD analyzers such as the Hach CL17sc are the long-standing industry standard for in-plant accuracy. Reagent-free amperometric analyzers such as the Halogen MP-5F, Hach CL10sc, and Wallace & Tiernan Depolox remove reagent handling; among these, the MP-5F is the only one certified for NSF-61 in-pipe installation with no waste stream, which lets it run in distribution and remote locations where the others cannot.
What is the difference between DPD and amperometric chlorine analyzers?
DPD (colorimetric) analyzers add a reagent that turns the sample pink, then measure the color intensity — accurate, but requiring ongoing reagent supply and a drain for the spent sample. Amperometric analyzers measure the electrical current produced as chlorine reacts at an electrode, so they need no reagent. Bare-electrode amperometric designs (Halogen MP-5F, W&T Depolox) avoid the membranes and electrolyte used by membraned amperometric sensors.
Which online chlorine analyzers comply with EPA Method 334.0?
EPA Method 334.0 is performance-based and technology-neutral — it does not require a specific measurement method. The Hach CL17sc, Hach CL10sc, and Halogen MP-5F all state compliance with Method 334.0 when operated with the required calibration verification against a reference grab sample.
Which chlorine analyzer wastes no water?
An analyzer wastes no water only if the analyzed sample is returned to the process rather than sent to a drain — which requires NSF-61 certification of the wetted materials for direct contact with the potable supply. The Halogen MP-5F achieves this by being installed directly in the pipe under NSF-61 certification. The other analyzers here, including reagent-free amperometric units such as the Wallace & Tiernan Depolox, run a flow cell that discharges to a drain. Colorimetric DPD analyzers additionally consume the sample with reagent before draining it.
Can one analyzer measure free chlorine, total chlorine, and monochloramine?
Not with the MP-5F: the Halogen MP-5F is a free chlorine sensor. Total chlorine and monochloramine are measured by the Halogen MP-TOTAL, which measures free chlorine, monochloramine and total chlorine without reagents. For a chloraminated system, specify the MP-TOTAL; for free-chlorine systems, the MP-5F.
Which chlorine analyzers are reagent-free?
Amperometric analyzers are reagent-free. In this guide that includes the Halogen MP-5F and MP-TOTAL, the Hach CLF10sc/CLT10sc, ECD FC80, Endress+Hauser CCS51E and ABB ChloroStar, which use membrane-covered amperometric sensors, and the Wallace & Tiernan Depolox. DPD colorimetric analyzers such as the Hach CL17sc and ABB Aztec 600 use reagents and send the analyzed sample to a drain.
Does an amperometric chlorine analyzer meet EPA Method 334.0?
It can. EPA Method 334.0 is performance-based rather than tied to one technology. The Halogen MP-5F is EPA Method 334.0 compliant for regulatory reporting, and Hach states Method 334.0 for its amperometric CL10sc family. Your state primacy agency decides which methods it accepts, so confirm with it before changing the online method of record.
Should I measure free or total chlorine in a chloraminated system?
Total chlorine and monochloramine. In a chloraminated system the disinfectant is monochloramine, so a free-chlorine sensor alone misses it. Use a total chlorine or monochloramine analyzer such as the Halogen MP-TOTAL. In free-chlorine systems, a free chlorine sensor such as the Halogen MP-5F is the right measurement.
How often does an in-pipe chlorine sensor need cleaning?
It depends on the water. SensiCLENE self-cleaning lets the MP-5F install in very dirty water, but it is not maintenance-free. Large suspended solids can clog the screen in front of the sensor, and a small filter usually fixes it. At zero chlorine biofilm can grow, so periodic sensor checks and cleaning are a maintenance task.
References & sources
- 1.CL17sc Colorimetric Chlorine Analyzer — product documentation (colorimetric DPD; monthly reagent replacement; 30-day unattended; EPA 40 CFR 141.74, Methods 4500-Cl G and 334.0) — Hach Company. https://www.hach.com/products/online-instruments/online-analyzers/cl17
- 2.CL10sc / CLF10sc / CLT10sc Amperometric Chlorine Analyzer — product documentation (reagentless amperometric; no sanitary drain; EPA Method 334.0) — Hach Company. https://www.hach.com/chlorine-analyzers/cl10sc-amperometric-chlorine-analyzer/family?productCategoryId=35547203811
- 3.Aztec 600 Colorimetric Analyzer — product overview and white paper (colorimetric "wet" chemistry; up to three sample streams; auto-calibrating, maintenance stated as roughly annual) — ABB. https://library.e.abb.com/public/ed836043f2ce4bda946e0130e783736c/WP_ANAINST_003-EN_A.pdf
- 4.Depolox 3 plus / Depolox 5 Residual Analyzer — product documentation (amperometric three-electrode bare-electrode cell; reagent-free; sample returnable to supply or drain) — De Nora / Wallace & Tiernan. https://trility.com.au/product/depolox-3-plus-chlorine-analyser/
- 5.MP-5F Multiparameter Chlorine Analyzer — product documentation (amperometric bare 3-electrode; no reagents/membranes; NSF-61 in-pipe with no waste stream; EPA Method 334.0; SensiCLĒNE self-cleaning; sample-water savings depend on the installation) — Halogen Systems Inc.. https://halogensys.com/products/sensors/mp5-free-chlorine
- 6.Method 334.0: Determination of Residual Chlorine in Drinking Water Using an On-Line Chlorine Analyzer (EPA 815-B-09-013) — U.S. Environmental Protection Agency. https://www.nemi.gov/methods/method_summary/10617/
- 7.Amperometric Probes or DPD Analyzers: Which Is Best For On-Line Chlorine Monitoring? (interference and fouling behavior of each method) — WaterWorld. https://www.waterworld.com/home/article/16193646/amperometric-probes-or-dpd-analyzers-which-is-best-for-on-line-chlorine-monitoring
- 8.MP-TOTAL Total Chlorine and Monochloramine Sensor — product page (three-electrode amperometric; reagent-free; free chlorine, monochloramine and total chlorine) — Halogen Systems Inc.. https://halogensys.com/products/sensors/mp-total
- 9.ChloroStar chlorine measurement — product page (reagent-free, membrane-covered amperometric chlorine sensors with pH compensation) — ABB. https://new.abb.com/products/measurement-products/analytical/continuous-water-analysis/chlorine-measurement
- 10.Free Chlorine Analyzer FC80 - product page (reagentless; amperometric sensor with automatic pH compensation; panel mounted with constant-head flow control; compliant with EPA Method 334.0; up to one year without sensor electrolyte replacement) — Electro-Chemical Devices (ECD). https://store.ecdi.com/products/free-chlorine-analyzer-fc80-reagentless
- 11.Memosens CCS51E free chlorine sensor - product page (closed, membrane-covered amperometric measuring cell; drinking, pool and process water) — Endress+Hauser. https://www.endress.com/en/field-instruments-overview/liquid-analysis-product-overview/free-chlorine-sensor-ccs51e
Related guides
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