Sanitizer Test Strips

Whether you use the three-sink method or a warewasher, it is important to sanitize your restaurant's dishes in addition to washing them. Sanitization, as defined by the U.S. Food Code, is any method used to reduce the presence of microorganisms on a surface by 99.999 percent.1 This sanitizing step may be completed with either chemicals or hot water, but in either case certain parameters must be reached to ensure a sufficient amount of bacteria is killed. Sanitizer test strips are one way to ensure those levels are achieved to protect your customers from foodborne illnesses.

Chemical Sanitizers

One of the most common ways of sanitizing dishes is by using one of several chemicals that have been proven to remove microbes such as bacteria. The three most commonly used chemicals for sanitizing in a restaurant are chlorine, quaternary ammonium, and iodine. Each one must be used in a specific concentration, and using too little or too much of the chemical in your sanitizing water can be dangerous.

While each chemical manufacturer's instructions describe the ratio of chemical to water to use, there are some mitigating factors that can make maintaining those levels difficult. Most sinks do not have volume demarcations inside their bowls and many employees do not take the time to measure out the water going into the sanitizing sink, instead "eyeballing" the amount. That can lead to inaccurate dilutions. Additionally, the mineral content of the water, measured in hardness and softness, can have an impact on how the chemical mixes with it, making the correct concentration difficult to achieve by simply measuring. Because of this, it is important to have sanitizer test strips on hand to confirm the correct concentration of sanitizer each time.


Chlorine, also known as bleach, is one of the most commonly chosen sanitization methods. It is widely available and inexpensive, but also carries with it a distinctive odor that may be unpleasant if it lingers on dishes. Additionally, chlorine loses its sanitizing power quickly as it is exposed to oil and organic materials, which can make it less effective if the sanitizing sink becomes contaminated. Because of this, the chlorine mixture must be changed out more often than those made with other chemical sanitizers.2 A chlorine sanitizer solution should have a concentration of 50 to 100 parts per million (ppm) in water between 75 and 100 degrees Fahrenheit, with a required contact time of at least seven seconds. Chlorine test strips are available to help you ensure the correct solution is created. The paper is dipped in the water, then turns a shade of gray that can be compared to a scale provided with the test strips, with most scales ranging from 10 to 200 ppm.

Quaternary Ammonium

Quaternary ammonium sanitizes dishes by using its positively charged cations to bond with the negatively charged particles of undesirable microbes. These sanitizing solutions are often called quaternary ammonium compounds (QACs) or quats. Quaternary ammonium is often preferred over chlorine solutions because it is noncorrosive, so it will not pit stainless steel over time. Additionally, ammonium is nonirritating to skin and, since it has detergent-like properties, it can handle more soil than chlorine before it needs to be changed. However, quats often do not function well in hard water, making testing an important part of any quaternary ammonium sanitation regimen. Quat test paper measures the concentration of the quaternary sanitizer in the water, using a color scale ranging from 0 to 500 ppm. This test paper is available in pre-cut strips and in tear-off rolls. Most quaternary ammonium sanitizers require dilutions of 150 to 200 ppm in water that is at least 75 degrees Fahrenheit, with the dishes submerged for at least 30 seconds.


Iodine, while not as common as chlorine or quaternary ammonium, has some benefits for restaurants that choose to use it. This sanitizing solution is brown, with the color indicating the strength of the solution, which can discolor some wares. Iodine is not affected by the hardness of your water, but it is more susceptible to its pH, working better in water that is slightly acidic. While it is not as long-lasting as quaternary ammonium, it lasts longer than chlorine in the presence of organic compounds. Iodine is also easier on skin than chlorine, though not as gentle as quaternary ammonium. This sanitizer should be used at 12.5 to 25 ppm in water that is at least 75 degrees Fahrenheit, but no more than 120 degrees Fahrenheit. Iodine test strips are available to help ensure this solution is kept at the proper dilution, as the color alone is not enough to determine the level. Please note that iodine is not approved in all locations for use as a sanitizer, so check your local codes.

Hot Water Sanitization

Another method of sanitizing dishes is with water that has been heated to at least 180 degrees Fahrenheit. In a compartment sink, this is achieved with a circulating water heater. It's easy to check the temperature of the water, as the sink is open and can be accessed by thermometers. However, in a warewasher, checking the temperature of the sanitizing rinse is a little more difficult.

In order to allow operators to check the temperatures of the water in their warewashers, temperature test strips are available. These are made to stick to the inside of the dishwashing machine where the water will hit it. Each strip has a colored stripe on it that will disappear when a certain temperature is reached. Strips are available that test for 160 and 180 degrees, so operators can check wash, rinse, and sanitizing temperatures.

Another method of checking the temperature of the water in a dishwasher is to use a thermometer. This will only work with a thermometer made and approved for that purpose, as they are made to record and save the highest temperature recorded during a wash cycle. Other types of thermometers will not give a proper reading, and in many cases will not function properly after going through the dishwasher.

  1. 2013 Food Code. U.S. Food & Drug Administration. Accessed September 2017.
  2. Chlorine Bleach as a Sanitizer. Oklahoma State University. Accessed September 2017.