Hot tub water balancing

nanobooboo

Bronze Supporter
Jul 20, 2019
16
Cottageville SC
We've added a new hot tub. I have read and reread Nitro's article "using chlorine in a hot tub" article. How do I use Chlorine in my Spa (or pool)?
It has a ton of great info, but I'm wondering if there is a "Cliff notes" version of the hot tub testing procedures? In trying to overcome my learning curve, I've taken sections of the hot tub/chlorine article and cut and pasted it into a document, but I haven't found enough info to validate my procedure or the order of testing. So if one exists, I'd love to see it posted here. I posted this the other day under the hot tubs forum - hopefully someone with more knowledge and experience will tweak. Again, this is all Nitro's work, I just cut and pasted for my own field use (and ADHD issues...)


Hot tub water balancing​

1. test CH:
If your CH is much below 100 ppm, you should add calcium to bring it up to 130-150 range. If your CH is over 100, you can leave it alone and just make a note of what it is.

2. test TA:
If TA is too low, add Baking Soda to raise it. If TA is high, you'll need Acid (Dry or Muriatic). Depending on how high your TA is will depend on how long it will take you. Plan on it taking around an hour to decrease TA by 100 ppm. So if your TA is 300 ppm, plan it taking around 2-3 hours. First, uncover your tub and turn on all your jets, air, blowers, waterfalls etc. Test your pH. When it's greater than 7.8, add enough acid to bring it down to 7.0. Keep aerating until your pH is 7.8 again (about 30 min), then add more acid and repeat. Every time you add acid you're lowering your pH and TA. When you get your TA tuned perfectly, your pH will rise to a level (i.e. ~7.6) and stop, then you know you're at your ideal TA level. If your pH is rising too high (>8.0), bring your TA down a little more. If your pH doesn't rise enough from aeration (after an hour or more), you over shot it and need to add a little Baking Soda to raise your TA. After a few days/weeks of monitoring it, you'll get your TA tuned perfectly. You may need to add a little Dry Acid once a week or two, but your water should be well balanced at that point.

Lastly, there is one more thing I haven't mentioned that you can add to your tub that will help buffer your pH, Borates. The easiest way to add Borates to your tub is to get a product called Gentle Spa. It is pH balanced, so there is no need to add acid to counter balance it. The ideal amount is ~50 ppm, and only needs to be added once per water change. That will help keep your pH from drifting from aeration. Not to mention, actually make your water feel silkier. I highly recommend it.


Water Balance

1. if your CH is much below 100 ppm, raise it to ~150 ppm. Otherwise, make a note of it.
2. Adjust your TA to ~50 ppm. Use Baking Soda to raise it (unlikely to be needed), or Acid/Aeration method to lower it. It takes ~8 oz Dry Acid to lower TA by 100 ppm in a 350 Gal Tub. Don't add it all at once!
3. pH should be between 7.2-7.8. Aerate to Raise pH. Acid to lower it.

If pH creeps up too much (>8.0), lower TA. If pH is too low, and doesn't raise enough by aeration, raise TA.
Add ~50 ppm Borate. (Borox/Acid or Gentle Spa)

Calcium, Baking Soda, Dry Acid and Borates is all you need to balance your water.
Use PoolMath to calculate exact amounts to add.

Sanitation

1. On a fresh fill use Dichlor until you get to 20-30 ppm CYA. (10 ppm FC = 9 ppm CYA)
Then switch to plain bleach or liquid chlorine.

Never let FC drop to Zero for any length of time. Keep it between 3-6 ppm normally, min of 1 ppm, and shock to 12 ppm once a week.
Use MPS if needed before hot tub party's and/or once a week to help oxidation. Don't use more than needed, because it's acidic and may lower your TA/pH.

Dichlor, Bleach and MPS is all you need to keep your tub sanitized.
Use PoolMath to calculate exact amounts to add.

Lastly, get a drop test kit such as the Taylor K-2006 or a TF-100. Also get FC test strips. They come in handy for a quick FC estimate, during parties, etc. The only two things you need to check regularly are FC and pH. Check them every day and after soaks. Adjust TA as needed. If you have your water well balanced, you'll rarely need to adjust your TA. You'll just be adding chlorine every day, and after soaks. Shock once a week, and/or after high bather loads. Use MPS if you have party's, and/or don't want to use as much chlorine. Easy as can be, and your tub is always ready.

TARGETS:

FC:
3-6 ppm ** NEVER less than 1 ppm; shock to 12 ppm weekly **
CH: +/- 150 ppm
TA: 50 ppm ** most important **
CYA: 20-50 ppm
pH: 7.2 - 7.8