Hot tub chemical testing and pool math calculator...

nanobooboo

Bronze Supporter
Jul 20, 2019
19
Cottageville SC
So I'm a great fan of TFP's pool math and used it to SLAM my green monster pool. Success! Thank you to all who continually contribute to this site!

Now we've added a new hot tub. I have read and reread the "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 was totally spoiled by PaulR - we printed and laminated his one page pool water testing instructions and keep it in the kit. What a time saver! Water Testing Instructions on One Page

My second question is about using the pool math app itself. When I open it, my pool info appears. How do I find where to enter the hot tub data? Do I have to delete the pool logs?

I appreciate all the time folks spend sharing their experiences...
:cool:
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
11,721
Northern NJ
My second question is about using the pool math app itself. When I open it, my pool info appears. How do I find where to enter the hot tub data? Do I have to delete the pool logs?
Upper left three line menu - Switch Pool- create new pool for your hot tub.

Why don’t you share the simplified instructions for Hot tub chemical testing that you created and let folks comment on it?
 

nanobooboo

Bronze Supporter
Jul 20, 2019
19
Cottageville SC
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 parties 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
 
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QuiltinMom

Platinum Supporter
Mar 24, 2013
202
Central Iowa
Great question. I have been wondering the same thing.

Had a pool, in.the process of getting rid of it. Got a used hot tub. Would love to have a short testing version of the instructions that came with the testing kit. Like which parts do I need to test for a hot tub and what are my goals.

I tried to also add my hot tub to pool match. I keep getting an error message. Still trying to sort that out.

My numbers seem to be WAY out of balance, so I need to do some adjustments soon.
 

nanobooboo

Bronze Supporter
Jul 20, 2019
19
Cottageville SC
Upper left three line menu - Switch Pool- create new pool for your hot tub.

Why don’t you share the simplified instructions for Hot tub chemical testing that you created and let folks comment on it?
:cool:OK, I posted it for review. Let me know what you think...hopefully it is of some use...
 

calstar

Well-known member
Feb 28, 2014
71
santa barbara, california
"....The easiest way to add Borates to your tub is to get a product called Gentle Spa. It is pH balanced...."

I believe I saw posted on this forum that the new Gentle Spa(new owner or new formula) is not pH balanced so be aware of that.