CYA levels… how did that happen?

[Newdude]

I would imagine the CYA mixes better/quicker in a spa. I notice a vast difference in adding CYA from the early spring with cool water and mid season with warm water. It might take me days to get the spring batch dissolved and the July dose is mush in 10 minutes. A 100+ degree spa that's all jetty (I agree @kul ) would break it down and have it evenly dispersed quickly IMO.

 

[Bperry]

A second question though… I can assume that my hot tub was at 1ppm overnight. Is that a big issue? It’s not been brought back up to 5ppm. I should also mention that it does also happen that overnight my UV/ozone cleaner (Jacuzzi’s Clearray) is also running.

The UV/ozone thing breaks down chlorine so not surprising.

 

[duraleigh]

Is that a big issue? Probably not but I would suggest an OCLT to look at chlorine consumption

 

[Mdragger88]

With ozone & uv along with the fact its a hot tub passing an
Overnight Chlorine Loss Test even if everything is fine is a little tough to do. A hot tub always eats.

To sure your bets,
Raise fc to somewhere between high target & slam level for your cya to help compensate for your missed dose & from here on out be sure to maintain fc ABOVE minimum for your current cya of 50.
Don’t worry- with the hot water the cya will likely degrade a little sooner rather than later.
No need to freak out about the difference between 40 & 50 ppm cya (35 counts as 40 for chlorination purposes - always round up if between two values)
Just chlorinate accordingly
FC/CYA Levels

 

[Andrew Montreal]

The UV/ozone thing breaks down chlorine so not surprising.

Indeed That’s why I mentioned it. Realistically it wasn’t at 1ppm before that cycle began so it it was probably only in the 1ppm range for half of one night.

 

[Andrew Montreal]

Nice! Something new to discover about my hot tub. I’ll admit… I do love all this investigation and experimentation.

 

[Andrew Montreal]

With ozone & uv along with the fact its a hot tub passing an
Overnight Chlorine Loss Test even if everything is fine is a little tough to do. A hot tub always eats.

To sure your bets,
Raise fc to somewhere between high target & slam level for your cya to help compensate for your missed dose & from here on out be sure to maintain fc ABOVE minimum for your current cya of 50.
Don’t worry- with the hot water the cya will likely degrade a little sooner rather than later.
No need to freak out about the difference between 40 & 50 ppm cya (35 counts as 40 for chlorination purposes - always round up if between two values)
Just chlorinate accordingly
FC/CYA Levels

But realistically, it can’t be at 50ppm seeing as not only does the math not add up, I haven’t added dichlor since my last test. I am going to presume that I am below 40ppm.

That being said, I intuitively did what you suggest… I brought the chlorine levels up quite a bit. In fact, I will once again add more before going to bed.

Thanks as usual for all the input.

 

[Mdragger88]

If this is a new tub you may also have your volume off a scootch. For instance my tub says its 250 gallons but I use 200 gallons in Poolmath as that seems to be more accurate with the results I achieve from my doses.
It is also easy to add a dab more than you mean to when measuring such small amounts unless you’re using a scale for everything (this is not necessary).
These things can result in the differences you describe. Aside from the margin of error (due to lighting differences) for the cya test. The best way to achieve consistency there is to do the test the exact same way, with the same lighting conditions every time.
Its really no sweat- just keep fc a little higher to sure your bets & keep nasties at bay.
We don’t recommend skirting minimum fc anyway.