We recently heard from ‘Kari’ who asked, “Hello! I was wondering if the Water Works Water Quality Test Strips keep longer if refrigerated? Or would this ruin them? Best way to store? Thanks! Kari”

Believe it or not, we have heard this question quite a few times in recent years. It generally costs less to purchase water test strips by the case or in bulk so a person wanting to extend the shelf-life of their inventory of testing supplies makes total sense… except for one small problem: Manufacturers use the stated shelf-life of products as the ‘last date at which they will guarantee product performance’ and no storage method will cause them to extend that date (for legal reasons).

For emphasis’ sake, as stated, no manufacturer we know of will guarantee longer shelf-lives of their products beyond stated dates regardless of storage conditions, but having worked with test strips for as long as we have, we have found that most of the products we tested worked as expected past expiration dates as long as we stored products using the following guidelines:

  • Keep all unused bottles sealed tightly. Keeping environmental moisture (humidity) away from the test strips helps to prevent premature decomposition of some chemical reagents.
  • Make sure storage conditions remain dry (i.e. no water and low humidity) at all times. It would SURPRISE you how many people do NOT keep their testing products out of potentially wet environments.
  • Do not store products in direct sunlight. Heat and UV rays accelerate the decomposition and/or degradation of chemical reagents.
  • Keep temperatures in the range specified by manufacturers. We suggest keeping products at the lower end of the temperature range. Do NOT allow storage temperatures to fall below freezing as this could also result in the degradation of chemical reagents.
  • And finally, if you have the ability, run controlled experiments pitting known good (in date) strips against technically expired strips to see how the results from each compare.

Again, the expiration date on a package of test strips represents the absolute last day that the product’s manufacturer will guarantee the product’s performance. Example: Exp 8/2020 means the product is guaranteed to perform as expected until the last day in August of 2020.

As far as refrigerating test strips to lengthen shelf-life, no manufacturer we know of would go on record as suggesting that… and we suspect that not all test reagents would take kindly to colder temperatures and/or have their shelf life made longer by colder temperatures.

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