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 Read the EPA Letter   View EPA Approved methods   Check w/ Your Local Health Department for Final Word on Compliance
Number of Tests:	100 Tests per Package	50 Tests per Package
Benefits:	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.

“Overview: This standard covers point-of-use (POU) shower filtration systems, designed to reduce free available chlorine that may be present in potable water (public or private).” (source)

Free Chlorine Water Test

The USEPA has set the Maximum Contaminant Level (MCL) for free chlorine in potable water at 4.0 ppm.

This means water dispensed by a water stystem must contain less than 4.0 ppm free chlorine… or the system is in violation of Federal Law and subject to geting fined and/or shut down by the USEPA if their free chlorine readings continue to exceed Federal Guidelines.

How do they test for free chlorine residual?

As a general rule, most water treatment facilities use a method called “DPD Testing” to determine the free chlorine concentration in the water they distribute. Click here for more information on DPD Testing.

As of Spring 2007, though, the USEPA began allowing states to approve the use of an alternate, yet equal, faster method called SenSafe(tm) Free Chlorine Water Check. This method does not use liquids, tablets, powders or even meters, yet provides accurate free chlorine readings down to as low as 0.05 ppm. Click here for more information on SenSafe(tm) Free Chlorine Water Check.