Spa Borate Question

[wjr75]

Hello,
I have a pool and spa with overflow. We just closed the pool and have the spa open. I want to continue using the BBB method. It looks like I should add some borax to increase my Borates to 50ppm according to Chem Geek from a previous post. Is this right?? The pool calculator indicates 51oz borax and then 25oz of muriatic acid. Is this a good plan?? My TA is 120ppm right now. I only keep the hot tub open for another 2 months into December. My spa is 900 gallons.

 

[chem geek]

That would be if you were using the Dichlor-then-bleach method and if your spa water was largely isolated from the pool. You would need to lower your TA first before adding the borates. If you have a lot of mixing of water between your spa and your pool then you might be better off managing the spa water more like your pool, but keep an eye on the pH since it will tend to rise much more in a spa due to the aeration from jets and the hotter water temperature. However, it sounds like "closing the pool" means that you aren't mixing the water so much.

Note that you could use boric acid instead of Borax and acid. Up to you.

 

[wjr75]

I just retested my TA and it is 80ppm, CYA after draining some water is 45ppm. I just ordered some boric acid from the dudadiesal. Does the borates just help to keep the PH in check or is there another benefit for it such as less skin dryness? Does the TA need to be at 50ppm before using borates? Thanks for the advice!

 

[chem geek]

It's easier to get the TA down to 50 ppm before adding the borates. The borates are for additional pH buffering, especially against a rise in pH. Any other benefits are incidental.

 

[wjr75]

Thanks for the replies Chem Geek. One last question with a 50ppm CYA do I still use the CYA/chlorine chart targeting 6ppm with a minimum 4ppm with bleach? In one blog you indicated that the chart isn't accurate with spa's. Not sure how to read into that. Also the one Spa school article indicates you can drop down during a soak to 1ppm as long as you bring it back up afterwards.

 

[chem geek]

We normally say to use around 30-40 ppm CYA so with 50 ppm CYA I'd have the FC target at the start of a soak be at least 2 ppm (not 1 ppm). Is the spa covered so no light gets into it? If so, then a lower FC at the start of a soak works (it will be higher after and in between soaks). If the spa is uncovered, then there is the risk of algae so the FC/CYA chart would be more applicable though algae don't like the very hot spa temperatures.