Newb Chemistry Questions

[kellyjo7]

First, thanks for all the info on this site, the pinned threads have been helpful.

I just moved into a new house with a ~500 gal 2005 Cal Spa tub. I was able to drain and refill and have been working on balancing. I'm using bromine for sanitation and the hot tub has an ozone.

My hardness is normal if not a bit on the low side, forgot the exact number.

I was having issues with high PH ~8-8.1 and Low TA. Like around 30-50 if not lower.

My main question is that I seem to see conflicting info on here about how big of an issue low TA is. I was finally able to get PH in perfect range, but my TA is very low like around 30.

I added a little TA up from spadepot.com last night after I tested the PH. I haven't got a chance to re-test, but I am concerned that it will creep my PH up again.

I'm using a Taylor Bromine K-2106 test kit. My Bromine Level has been good, though it trends a bit on the high side (between 5-10, though it was actually a little low on Sunday, so I increased the dispenser and it's back in the 5-10 range, probably right around 6.5-7).

It's been about a month, and I've noticed some pretty decent water loss, we use it ~4 times a week. And I'm in South Dakota so it''s usually cold. So I imagine that's the reason for the water loss. I need to top it off tonight, so this A.M. I opened up the bromine dispenser up again to about 5.5.

So I guess my two questions are:

1. Is low TA okay, if I keep PH in proper range? If yes, how low is too low?

2. What do I need to consider/anticipate when topping off, I opened up the bromine because I figure when I top it off it will dilute the sanitizer, maybe this thinking is totally off. What will be the top off impact on my chemistry? I'm assuming I will kind of have to start fresh after topping off. I shock at least once a week with OxySpa MPS. Should I shock again after refilling?

Thanks!

[chem geek]

So long as you don't have a plaster spa or grout in tile exposed to the water, the low TA is OK but you should probably have some supplemental pH buffering just in case so could use 50 ppm Borates (most easily added from Boric Acid). If you do that, then your TA could probably be at 40 or 50 ppm and not have too much of a pH rise.

Evaporation and refill results in adding to the water whatever is in your fill water, usually increasing TA and CH.