How long will a sample of pool water stay "good" for testing?

[sccm_sysadmin]

Right now I'm trying to slowly convince one of my co-workers to switch from using traditional chlorine pucks and test strips to the TFP method. He just opened his pool this weekend and we were chatting about it.

I was thinking of asking him to bring in a sample of pool water large enough to run the entire battery of tests with my TF-100, but I'm not sure if the water sample would stay "good" in-between the time it is removed from the pool and when we would get to work in the mornings so I can get an accurate reading (as in: would any chlorine levels decrease, would the pH change, etc).

I'd imagine that a quick sample that was sealed and brought immediately into work with a relatively short commute, kept out of direct sunlight, and tested first thing in the morning when we walk in the door would probably be pretty accurate. Thoughts on my idea?

 

[Richard320]

I'd expect pH to go up a hair and FC to come down. Don't worry -- the CYA and/or CH buildup and the low TA from acidic pucks will all show up.

But don't worry about it. Your coworker probably drives a sample to the pool store to get it tested anyway. So you're comparing apples to apples this way.

 

[sccm_sysadmin]

Thank you sir! Apparently he does the test strips himself and plugs them into the Chlorox app on his phone which tells him what to do.

He showed me his most recent numbers from yesterday, regardless of how accurate or inaccurate they are: FC 0, TC (??), pH 7.8, CYA 100, CH 500, and I can't remember what his TA number was. Hopefully I can convince him to bring in a sample.

As a side note it's also not "his" pool, he rents the house and it happens to have a pool. He told me that according to his lease, his landlord will open and close the pool but he is responsible for upkeep.