We get a lot of questions dealing with DPD and today we received an inquiry from ‘Krystee’ who asked, “How do the DPD ReagentStrips differ from the SenSafe chlorine test strips and would I need to buy a meter to use them?”

Although both manufactured by Industrial Test Systems, Inc., a US based company in South Carolina, the DPD-1 ReagentStrip and SenSafe Free Chlorine Water Check products test for free chlorine residual in very different ways.

The chart below will explain the differences and similarities between the two free chlorine residual test methods:

  DPD-1 ReagentStrips™ SenSafe™ Free Chlorine Water Check
Detects: Free Chlorine Residual (and Other Oxidizers Normally Tested Using DPD-1 Chemistry) Free Chlorine Residual
Test Procedure Overview: Liberarting of DPD-1 Reagents Off Reagent Pads Into 10mL Sample and Checking Chlorine Concentration Visually by Color Comparator or Electronically Using a Colorimeter Immersion of Test Strip in Water Sample, Removal of Test Strip After Specified Period of Time, and Visual Comparison of Developed Color in Test Area to a Color Chart
Detection Range: 0-6ppm 0-6ppm
Accuracy & Precision: Depends on the Method Used to Interpret the Developed Color in the 10mL Sample. Visual Methods Will Have Less Precision Than Meters 0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 1.5, 2, 2.6, 4, 6 ppm (mg/L)
Certifications & Compliance: DPD Testing as Specified in 4500-CL G

  • Check w/ Your Local Health Department for Final Word on Compliance
USEPA Approved Test Method for Free Chlorine

Number of Tests: 100 Tests per Package 50 Tests per Package
  • Cleaner to Use Than DPD-1 Powders (i.e. DPD-1 Powder Pillows)
  • Dissolves Easier Than DPD-1 Tablets
  • Longer Shelf-Life Than DPD Liquid Reagents
  • No Undissolved Solids When Testing in Cold Water (5ºC)
  • Requires No MSDS
  • Safe for Use on Most Production Floors
  • Requires No Specialized Testing Knowledge
  • No Expensive Meter (Colorimeter)
  • Designed to Resist Monochloramine Interference
  • Requires No MSDS
Per Unit Cost: $15.99 per Package of 100 Tests $15.99 per Bottle of 50 Tests

As always, if monitoring free chlorine residual for reporting and/or compliance monitoring we suggest contacting your local health inspector before switching to a different chlorine testing method.

Although seemingly counter-intuitive, many methods approved on a Federal level may not have attained acceptance, yet, on a State or Local level.