There is a handful of different methods for water quality testing, all of which have their own benefits and drawbacks. These methods are:

• Photometers and reagents
• Titration reagents
• Comparator test
• Test Strips

The most accurate of all methods to date is the photometric method (like our eXact Photometers) that use reagents, namely due to the fact that there is no visual color matching needed, taking out the subjectivity of the human eye. This method measures the transmission of light at a given wavelength through a color altered water sample; basically a measurement of light transmission is taken before the sample is altered (called zeroing) and after the sample is altered with a color changing reagent. The difference of light passing through the sample cell before and after is used to calculate the result. This results typically in a resolution of 0.01ppm in most cases.

Secondly we have the Colorimetric (or visual) Titration method, which uses chemistries that alter the color of a water sample, and the concentration is then determined. These tests are cost effective, however do take some technical abilities, such as being able to accurately judge color change, carefully introduce and count drops to the water sample, and the ability to do quick math on site. Typically this testing method has a resolution anywhere between 0.2ppm and 20ppm depending on the kit and the parameter being tested.

Another popular testing method is the Color Comparative method. A lot like the Colorimetric method, these tests are relatively inexpensive and are widely accepted among commercial testing, however do suffer from stability issues, require good visual judgment and give only a minimal resolution, typically 0.4 for pH and 1ppm for Chlorine.

One of the more common testing methods seen on store shelves and widely available to the home owner or residential pool maintenance company are Test Strips, this method is quick and easy to use, inexpensive, and are more stable than liquid reagents giving them a better shelf life. While test strips are a great inexpensive tool for quick screening of pools and getting a ballpark result, they are not ideal due to poor resolution and require good color matching abilities. The typical resolution of this method is 0.4 for pH and 1ppm or greater for Chlorine.

Out of all of these methods, Photometric analysis is the most accurate way of determining water quality. Newer Photometers make field testing easy, and in some cases can be comparable in price to some other methods available after taking into consideration the upfront expense of the photometer.