Testing cold water

[no-mas]

Hi folks -
For those of us who do not close a pool... when testing over the winter, should water be allowed to come to room temperature, or is testing cold water ok? Anything else to be looking out for?

[JasonLion]

You should test FC and PH as soon as you take the sample. Before testing CYA it is best to allow the sample to come up to room temperature. TA and CH don't care so much if you wait or not.

[Johnny B]

.... Before testing CYA it is best to allow the sample to come up to room temperature. ...

Do you have a temp range range? Or asked differently, how cold is too cold? We open & balance in March, way before it is warm enough to swim, I'm guessing the water is 60 degrees (I'll check it this spring).

We test CYA in the summer when the water is quite warm

[polyvue]

Cold water affects CYA test
Taylor Technologies

Do pool or spa water samples have to be at “room temperature” before testing begins?

With one exception, no. Our lab has run the pH, total alkalinity, calcium hardness, free chlorine, and cyanuric acid tests on known standard solutions at approximately 104°F, 75°F, 60°F, and 40°F. Only at 40°F did the CYA standard solution test higher than its actual value (after accounting for test variability). All other tests were unaffected by temperature differences.

Source: http://www.taylortechnologies.com/Featu ... ntentID=91

According to the manufacturer of a test for CYA, it would appear that the sample would have to be colder than 60 degrees F. to impact the test result. I test CYA once a week throughout the winter and haven't noticed any difference -- but the coldest water I've brought in to the house to test started at 44 degrees, and I habitually test in kit order.... FC/CC, pH, TA, CH and then CYA.

[no-mas]

Thanks guys!

[PaulR]

chem geek has reported (unfortunately I don't find the link in my notes) that pH will vary by about .1 to .2 across the range of temps found in pools. Given the typical color-matching pH test in most test kits, that's about the minimum difference you can detect. So in practice, if your sample from the 40F pool warms up to 70F before you test it, it'll make a small difference.
--paulr

[JasonLion]

To put that another way, temperature does not affect the PH test, it affects the PH. The test correctly reports the PH at any (plausible) temperature, but the PH at warm temperatures won't be the same as what it was when the water was very cold. A very similar thing happens with the FC/CC test. The test works at any temperature, but if you allow time for the water to warm up the FC level of the sample will change (as chlorine evaporates out of the sample and increased exposure to sunlight affects the FC level).

Both of these situations are different from the CYA test, where the CYA level does not change, but the test results can change depending on water temperature.

[orthofish]

Thanks for asking that no-mas. I had been wondering the same thing, just hadn't gotten around to asking.
As usual, the answers were spot on

[polyvue]

So long as we're rooting around in the cellar on this topic, with Paul and Jason successful at finding the sweetest fungi among the more common species, I might as well 'fess up to several issues I noted with the Taylor pronouncement that may nuance its telling. One, the tests they performed are narrowly defined but generally described. Using only selected intervals in a set of possible temperatures it's impossible to know from the test data, for example, what impact a temperature of 50, 85 or 105 °F. would have on any of the tests; and the statement, "test[s] higher than its actual value", is indicative of direction but doesn't quantify the amount of impact. E.g., would it test half again as high, 4 times as high, etc.? Second, one would suspect that the lab conducted the tests against standard solutions made by Taylor, though the wording isn't specific in this regard. So, one can't be sure that a given sample of pool water containing higher or lower values (e.g., 600 ppm CH, 50 or 200 ppm TA, 20 or 80 ppm CYA) than the standard solutions used (Hardness Std 200 ppm, Alkalinity Std 100 ppm, CYA Standard 50 ppm) might produce a different outcome. There are other factors as well but this should suffice in giving one pause in ascribing too much authority to any generalization.

[no-mas]

....As usual, the answers were spot on

Yes, we are very spoiled here. Jason and Greg, Thanks again

[PaulR]

While we're on the topic, I can't say I've noticed the CH test being an actual problem with cold water, but... (I'm currently on vacation and don't have the kit in front of me, but as I recall) the R-0011 is kind of thick and doesn't like to mix in cold water. This means longer swirling time, but as I said not sure it affects the actual test.
--paulr