Hach CL17 chlorine analyzer replacement
This page covers the Hach CL17 and CL17sc as the DPD colorimetric family utilities actually replace. It is a factual comparison plus published field evidence — not a ranking of which instrument is “better.”
Quick Answer
Can the Halogen MP5 replace a Hach CL17 or CL17sc?
MP5 — best for
- Reagent-free free-chlorine residual at plants, wet-taps, tanks, and remote sites
- Sites that cannot run a conditioned sample panel or sanitary drain
- Operators targeting 6–12 month service instead of monthly reagent/cell work
Not best for
- Plants that must stay on EPA 4500-Cl G DPD colorimetric as the online method of record (CL17sc is that method)
- Total chlorine / monochloramine or nitrification — use MP-TOTAL, not MP5
CL17 / CL17sc — best for
- In-plant panels where DPD colorimetric is the required online method of record
- Sites already standardized on Hach DPD reagents, SC controllers, and sample panels
- Applications that need the published 30-day unattended DPD cycle Hach documents
Not best for
- Zero-flow, wet-tap, or tank sites with no sample panel or drain
- Utilities trying to eliminate reagents and a continuous waste stream
Crawlable comparison
Hach figures below are paraphrased from Hach’s current public CL17sc product page and published specifications. Where Hach does not publish a number, the cell says so instead of guessing.12
| Feature | Halogen MP5 / MP5-A | Hach CL17 / CL17sc |
|---|---|---|
| Measurement method | Bare-electrode amperometric (no membrane) | Colorimetric DPD chemistry (free or total chlorine, configured) |
| Reagents | None | Buffer + indicator; Hach publishes 0.5 L of each per 31 days on CL17sc documentation |
| Maintenance | Self-cleaning (SensiCLENE); annual wear-parts swap; typical service 6–12 months | 30-day unattended operation; monthly reagent change and colorimetric-cell cleaning (Hach CL17sc product page) |
| Installation | NSF/ANSI 61 wet-tap in-pipe, PVC tee, immersion, or sample panel | Side-stream / sample panel with conditioned sample and a drain (not an in-pipe instrument) |
| Sample flow | Flow-independent (HiRes impeller). Operating flow 0–4 m/s | Hach CL17sc documentation: 60–200 mL/min through the instrument |
| Waste | None on in-pipe / return-to-process installs — sample stays in the line | Spent sample and reagent exit a drain hose to a sanitary drain. Hach does not publish an annual waste-volume figure on the current product page |
| Calibration | Typically 6–12 months; verify against a DPD grab sample | Factory-calibrated DPD cycle; routine monthly cell/reagent service. Hach does not publish a 6–12 month calibration interval |
| Lifecycle cost | As low as ~$185/year (SensiCLENE beads $35/yr + pH cartridge $295 every 1–2 years) | Recurring reagent + monthly service. Hach does not publish an annual dollar figure on the current public pages, so none is stated here |
| Accuracy (published) | ±5% of reading or 0.04 mg/L (0.04 ppm), whichever is greater | See Hach’s current CL17sc specifications. Not restated here unless listed on Hach’s live product page |
| Best for | Plants and remote sites that want reagent-free residual, in-pipe or low-flow installs, and 6–12 month service intervals | Sites that must keep EPA 4500-Cl G DPD colorimetric as the online method of record, or that already standardize on Hach DPD panels |
| Not best for | Plants required to report from an online 4500-Cl G DPD analyzer; chloramine / nitrification (use MP-TOTAL, not MP5) | Sites that cannot accept reagents, a drain, or a conditioned sample stream; zero-flow / wet-tap mains without a sample panel |
CL17 is the legacy DPD instrument; CL17sc is the current DPD family member Hach documents as 30-day unattended. This table treats them as the DPD family utilities replace, not as two unrelated products.
MP5 published specifications
| Specification | Value |
|---|---|
| Free Chlorine Range | 0–10 mg/L (ppm) |
| Accuracy | ±5% of reading or 0.04 mg/L (0.04 ppm), whichever is greater |
| Response Time (T90) | 90 seconds |
| Operating Flow | 0–4 m/s |
| Communications | Modbus RTU |
Imported from Halogen Master Specifications via lib/sensor-specifications.ts.
Field evidence (quoted, not invented)
City of Lakewood, CA ran a six-month pilot alongside a Hach CL17. The MP5 stayed within 0.04–0.05 ppm of reference with zero calibrations.
“There are some sites that cannot be monitored due to the need for a waste stream. The Halogen MP5 solves this problem.”
Newport News Waterworks held the MP5 within 0.2 mg/L of CL17 grab comparison. The incumbent CL17 failed at six weeks; the MP5 took over SCADA.
“The Halogen outperformed other analyzers we evaluated in every category—stability, pH range tolerance, flow handling, and maintenance requirements. We intend to purchase one to replace the failed CL17 and add another at our wellsite.”
“I’m replacing all of our Hach CL-17 analyzers with MP5 units. They just keep running — no reagents, no tubing, hardly any calibration.”
Startup video
Closest published clip for a CL17-to-MP5 cutover: system startup and function testing. A dedicated replacement-walkthrough video has not been filmed.
Frequently asked questions
Is the Halogen MP5 a replacement for the Hach CL17 and CL17sc?
Utilities commonly replace the Hach CL17 / CL17sc DPD family with the Halogen MP5 when they want reagent-free residual, no sample-to-drain waste, and in-pipe or low-flow installation. The MP5 is not a drop-in DPD colorimeter. Plants that must keep EPA 4500-Cl G DPD colorimetric as the online method of record should stay on a CL17sc-class analyzer.
Does the CL17sc really run unattended for 30 days?
Yes — that interval is from Hach’s current CL17sc product page: the analyzer operates unattended for 30 days, and monthly routine maintenance includes changing reagents and cleaning the colorimetric cell.
What sample flow and waste does Hach publish for the CL17sc?
Hach’s published CL17sc specifications list sample flow of 60–200 mL/min through the instrument and a flexible drain hose for spent sample. Hach’s current product page does not publish an annual waste-volume or annual reagent-dollar figure, so those numbers are omitted here.
How did the MP5 compare to a Hach CL17 in the field?
City of Lakewood, CA ran a six-month pilot alongside a Hach CL17: MP5 stayed within 0.04–0.05 ppm of reference with zero calibrations. Newport News Waterworks held the MP5 within 0.2 mg/L of CL17 grab comparison; when the CL17 failed at six weeks the MP5 took over SCADA. Palm Beach County Water Utilities is actively replacing its Hach CL-17 fleet.
When should I not replace a CL17 with an MP5?
Do not replace a CL17sc with an MP5 if your online method of record must remain EPA 4500-Cl G DPD colorimetric. Do not use the MP5 for total chlorine or monochloramine / nitrification — that is MP-TOTAL, not MP5.
What does the MP5 cost to operate each year?
Halogen publishes MP5 operating cost as low as about $185/year: SensiCLENE cleaning beads at $35/year plus a pH cartridge at $295 every 1–2 years. That figure is a Halogen published cost, not a Hach comparison dollar amount.
References & sources
- 1.CL17sc Colorimetric Chlorine Analyzer — product page (colorimetric DPD; 30-day unattended operation; monthly reagent change and colorimetric-cell cleaning; US EPA 40 CFR 141.74) — Hach Company. https://www.hach.com/products/online-instruments/online-analyzers/CL17
- 2.CL17sc Colorimetric Chlorine Analyzer — published specifications (sample flow 60–200 mL/min through the instrument; 0.5 L buffer and 0.5 L indicator per 31 days; drain hose) — Hach Company. https://cdn.hach.com/7FYZVWYB/at/8fxxnw8q83mmx8r8tj3tbbw/DOC0535335300-CL17sc-Analyser.pdf
- 3.MP5 / MP5-A Multiparameter Chlorine Analyzer — Halogen Master Specifications (accuracy ±5% of reading or 0.04 mg/L, whichever is greater; flow 0–4 m/s; NSF/ANSI 61) — Halogen Systems Inc.. https://halogensys.com/products/sensors/mp5-free-chlorine
- 4.City of Lakewood, CA — six-month MP5 pilot alongside Hach CL17; 0.04–0.05 ppm of reference; zero calibrations — Halogen Systems Inc. / AWWA Opflow (April 2025). https://halogensys.com/resources/case-studies/lakewood-ca
- 5.Newport News Waterworks, VA — MP5 within 0.2 mg/L of CL17 grab comparison; CL17 failed at six weeks and MP5 took over SCADA — Halogen Systems Inc.. https://halogensys.com/resources/case-studies/newport-news-va
- 6.Palm Beach County Water Utilities, FL — actively replacing Hach CL-17 fleet with MP5 — Halogen Systems Inc.. https://halogensys.com/resources/case-studies/palm-beach-fl
- 7.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/
Author: Michael Silveri, Halogen Systems Inc.
Reviewed 2026-08-31. datePublished / dateModified 2026-08-31.