Does FC deplete in water sample left to sit?

[JamieP]

I wanted to check my FC overnight before the pool came on in the morning at 6:30 am. I was up with the baby at 3 am so decided to pull a sample then, in case I didn't feel like getting up at 6:30. When I tested the sample sometime around 7:30 or so, the FC was less than it had been last night. I figured I need to SLAM and went out to get some bleach at Walmart, but now I thought I should confirm that the sample, just by leaving it to sit those few hours, wouldn't have lost FC on its own. I was using a large syringe to draw the water and that's where the water was kept.

 

[Pool Tool]

I would disregard the results as a basis for any real decision. Any uv hitting the syringe would quickly diminish FC. There is enough inconsistency that I wouldn't consider it to be representative of the pool after sitting.

 

[JamieP]

I would disregard the results as a basis for any real decision. Any uv hitting the syringe would quickly diminish FC. There is enough inconsistency that I wouldn't consider it to be representative of the pool after sitting.

The syringe was sitting inside on my kitchen table, out of the sunlight. But you're right that I need to have a more trustworthy sample. Does that mean that I need to wait until tomorrow to see if I need to SLAM? I'm a little concerned and wouldn't mind getting started now that I have the bleach and have dropped the PH (which I did before heading to the store so it would be ready when I got home.)

 

[JamieP]

Bringing pool up to slam levels. It can't hurt

 

[tim5055]

Yes, the FC can degrade sitting in a bottle. As an aquarium owner for many years the common instructions was to let any water you were going to add to the tank sit for 24 - 48 hours to allow the chlorine to dissipate. We have even had some members discover that the container they use to collect the water had been contaminated and had it's own little algae colony consuming chlorine before testing could occur.

Always test as quickly as reasonably possible and allow any collection containers to sit open allowing it to air dry. Closed containers and in you case a syringe can harbor a damp environment where lots of stuff like to grow. Think of the moist environment in/around most showers, what we have to do regularly there to keep mold/mildew at bay?

 

[JamieP]

Thanks, Tim, that makes sense. I'll stay the course on the SLAM anyway since we've got guests coming Saturday and I don't want to have a bigger problem on my hands. Hopefully it's nothing, or something minimal that can be taken care of quickly.

 

[tim5055]

It never hurts and remember, it's safe to swim up to shock level.

 

[JamieP]

During a SLAM, do you check CC every time you check FC, or just after each OCLT to see if you've passed the SLAM? Mine keeps coming in at 0 and I don't want to keep testing if I don't have to.

 

[Pool Tool]

No need to test CC every time, it obviously has to be tested before ending the slam but otherwise isn't needed for anything during the slam.