Water sample questions

[manny_man]

Hey All,

Thanks for all the great information. I am a pool service technician and have found a lot of useful information here. I have kind of an odd question I thought I'd try. I just took home 20 water samples from some testing. I loaded them up in clean, empty water bottles. That was 8 days ago. They have been stored in my house where it is cool, with the caps firmly closed, and a towel laying over them so they were not in direct sunlight. Any ideas if these samples might have changed? I am planning to test for PH, TA, CYA, CH. I did some testing to see if CH might change over several weeks with some old samples and they tested the same, just not sure how/if other tests might be effected. Thanks for the help.

Manny

 

[duraleigh]

Welcome to the forum. :lol: That's way too long to expect accuracy. CYA and CH are pretty stable but I would never trust pH, TA, and FC much after an hour or so

 

[manny_man]

Thanks for the reply duraleigh. Im not concerned about checking FC, this work up is to check where my pools are on csi. Cya and ch are the most time consuming so I'm thinking I'll test for those with the samples i have and test the TA and PH while I'm at the pools next week. I'd love to hear Chemgeek's thoughts on the matter and some of the chemistry behind why they would not be accurate and what is the maximum lifespan a water sample can be held for. Thanks again

 

[JasonLion]

Chlorine breaks down over time, with sunlight, and is lost through outgassing. As the chlorine breaks down it changes the PH and TA levels. The PH change is often significant, the TA change is usually minor.

How long you can store the sample very much depends on the container and the storage conditions. A sealed glass container with very little air space above the sample stored in a cool dark place can last quite a long time for numbers like CH and CYA, but even under those conditions the FC level will tend to be off after not very long. An open top plastic container left in the sun can drift rather quickly due to sunlight effects and outgassing/evaporation.

 

[manny_man]

Okay good to know. The samples are in 12oz water bottles filled to within an inch to an 8th of an inch. He are tightly sealed and are in an a/c room. The room is bright but they are stored in a empty chlorine case with a towel over them so there is no direct sunlight. Based off what I'm hearing and how they are stored I can probably get reliable cya and ch readings correct? That should be a good start.

Thanks for the help.