Spa water gone wild

[Maestro]

Okay, because it's summer I've been a little lax about testing my spa water daily, but I didn't expect this!

7/3/16
Temp 103°
Bromine 6.625
pH 8.2
CH 400
TA 50

7/23/16 (today)
Temp 100° (that's ok, I turned it down last week)
Bromine 18
pH 6.8
CH 0 (the test water didn't change color at all when I added drops)
TA 0 (the test water turned bright red when I added drops)

I did have a small floater with bromine tabs in the whole time, and the spa has been covered. The floater had two out of its three slots lpen to release bromine.

I think I'll do a complete water replacement today anyway, but I'd love to know if anyone has an idea what could have gone so wrong with the water in three weeks!

 

[pooldv]

I am not very familiar with bromine use. But, I don't think it is possible for CH to go from 400 to 0. Trichlor pucks or dry chlorine products can cause your TA and PH to crash.

I assume you are following this process
How do I use Bromine in my spa (or pool)?

Use the info from this to manage your TA and PH, it has much better details. I have kept my tub this way for years and it is great.
How do I use Chlorine in my Spa (or pool)?

 

[Maestro]

I am not very familiar with bromine use. But, I don't think it is possible for CH to go from 400 to 0. Trichlor pucks or dry chlorine products can cause your TA and PH to crash.

I didn't think that was possible either, but I did both the CH and TA tests twice to make sure, and that's what I got. I've often seen my CH level go down in both my hot tub and my pool, and I understand that's unusual. I add calcium chloride to both on a fairly regular basis to stay ahead of it as best I can. I even posted on another forum on this site last year about the pool, and people told me it shouldn't be happening. I just can't figure out how it went all the way to zero in the hot tub in three weeks.

One other detail I forgot to mention: the bather load has been very light. My wife and I only use it once or twice a week, and I always put in oxidizer when we're done.