How Cold Temperatures Affect Your Pool/Spa Water

Yes…it’s cold…VERY COLD…especially out here on the East Coast. Record low temps, blizzards, and runs on the grocery store for bread, milk, and toilet paper (inside joke for us in the Baltimore area) make this such a “special” time of the year.

Brrrrrrr… As a result, this frigid weather has led to a barrage of calls and e-mails about testing pool/spa water with low temps. Imagine that! Seriously though, low temps can affect test results, reaction times, solubility within the sample, and reagent efficacy.

For example, it may take a few more drops of reagent in a total alkalinity or calcium hardness drop test before you see the color change, which will result in a false-high reading. In a pH test, some reagent components may precipitate when the reagent is added to a low-temp sample, causing faded test colors, inaccurate results, and/or no reactions at all! It’s also widely known that CYA testing of low-temp water will provide false-low test results (even at water temperatures in the 60s) because the speed in which the precipitate forms is slowed down tremendously. Other tests could be affected as well.

For test strip users, be aware that temperatures <45°F (7.2°C) can affect color development. And for those of you who use meters, you’ll be happy to know that low-temperature samples do not usually affect test results, but it would be wise to verify this by checking your meter’s specifications.

As a general guideline, we recommend not testing pool/spa water samples that are <45°F (7.2°C). Another important reminder: Store reagents and test kits in a temperature range of 36°F–85°F (2.2°C–29°C).

So, what’s the “get around”? If you must test pool/spa water <45°F (7.2°C), collect the sample from 18″ below the surface (again…brrrrrrr!) in an opaque container, bring it inside to a warmer environment, and wait a few minutes before performing the test. Remember…patience is a virtue!