TA check using the TF100 for spa water

[pooldawg]

Hi. After successfully using my TF100 test kit on my pool for the last month, it occurred to me to start using it to check my spa as well.......Duh!
Spa is roughly 500 gallons ( we think) and has an ozonator. We have always used a granular non-chlorine shock in the past, but just this week put in some liquid chlorine to shock (water was cloudy), which seems to work great so far. After chlorine shock, spa water was clear & all looked OK. Using the TF100, FC & CC were both 0 ppm. Initial Ph reading was well over 8.2; adjusted down to 7.5. When I tried to check the TA with the water temp at 101 F, the solution never turned green, but stayed red before any addition of the final solvent.....??
Not sure what this means as the TA test seems to work fine with the 86 F pool water....... advice, please.

 

[chem geek]

Normally an initial red would indicate 0 TA and a pH of around 4.5 or lower. Usually test test works OK even at hot water. You can let the water cool a bit to room temperature before testing, but perhaps your TA is just very low -- maybe close to 10 or so. Double check your test against pool water and/or tap water. You can add a small amount of baking soda to get your TA up to 40-50 ppm for the spa -- you don't want it much higher than that.

Also, read Using Chlorine in a Spa and consider using 50 ppm Borates (such as from Proteam Gentle Spa since the quantities you need are small).

 

[pooldawg]

Thanks, Chem Geek - pretty much what I figured...... had already double checked TA with pool water. Added enough baking soda to raise TA to 110, readjusted Ph to 7.5, and added chlorine to a FC level of 4ppm. Checked CH for kicks & grins, was 170ppm. All seems stable and spa is sparkling, but learned my lesson about just trusting the ozonator and occasional non chlorine shock. Might as well get my money's worth from the TF 100 test kit.

 

[chem geek]

If you are using the Dichlor-then-bleach method for the spa, then you'll want the TA to be a lot lower -- closer to 50 ppm -- to get pH stability. If you are using bromine or an acidic source or chlorine, then your TA might be OK though usually the aeration in a spa is far higher than in a pool.

 

[pooldawg]

Thanks again. Two weeks later, after adding some more water this morning, the pH = >8.2. Spa has looked great & we haven't used it more than a couple of times - didn't realize that aeration had such a drastic effect. Adjusted pH down to 7.5 and checked other levels; TA = 70; CH = 200; FC = 4; CC = 0; CYA = <20, probably 0 since I've never added any and have been using a little liquid bleach along with the ozonator. Guess I should check more often than 2 weeks. Question I now have is should I add CYA & if so, to what level - 20 to 30? Spa is outdoors but covered. Again, it's looked & felt better the last two weeks than ever. Anything I'm missing?

 

[chem geek]

Again, the TA can be lower to help prevent the pH from rising as much and you should then also use 50 ppm Borates. You should also have around 30 ppm CYA in the spa or else the chlorine will be too strong. Read Using Chlorine in a Spa for more info.

 

[pooldawg]

Used the pool Calculator - thanks Jason! - to determine the amount of CYA needed to bring spa to a level of 30 ppm. Will check in a few days to verify. Looked into borate options, sounds like Proteam Gentle Spa has a lot of believers, but I'd have to order online which means I need to check into shelf life and storage requirements. Are other borate products which might be locally available as effective and easy to use? I like the pH balance aspect of Gentle Spa, do any other borate products offer the same feature?

 

[chem geek]

For CYA, one normally just starts off using Dichlor initially in the spa until one has cumulatively added around 33 ppm FC, usually over a week, and then you switch to using bleach. Of course, you can add pure CYA directly if you want but it may be hard to get such small quantities of CYA.

ProTeam® Gentle Spa is mostly boric acid which you can buy at The Chemistry Store or at AAA Chemicals.