Gentle Spa or 20 Mule Team Borax?

[Maestro]

I've read some posts that suggest adding a product called Gentle Spa to make the water feel silkier. I also read that adding 20 Mule Team Borax and muriatic acid at the same time will do the same the thing. if that's correct, I'd rather do the latter since I already have those on hand.

The question is how much to add and how to do it? What number do I input in the "Target" column in PoolMath? Is it safe to mix the two products together in a bucket before adding, or do I add one to the spa after another?

 

[chem geek]

It's easiest to use boric acid, but since you already have the 20 Mule Team Borax and Muriatic Acid you can use those. In PoolMath you put in 0 for Now and 50 for Target for Borates. For your 430 gallon spa PoolMath says to use 25 ounces weight or 24 fluid ounces volume of 20 Mule Team Borax and 12 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid).

You do not mix those together outside the spa. Split the total dose into no larger than 1/4ths and add the acid first, then the Borax, then the second dose of acid, then the second dose of Borax, etc. You can just mix for a few minutes in between if you have strong circulation in your spa such as some jets running (careful about splashing -- always wear eye protection when adding Muriatic Acid). It's somewhat safer to split the dosage into 1/8ths (with 50 ppm TA it has the pH drop from the first acid addition to 6.7 instead of 6.2) and you can see that this is far more work than using boric acid which is just a single chemical addition.

 

[Maestro]

Thank you for the prompt response, chemgeek. I'll start on this this evening.

Once I've added the chemicals, how do I test the borate level? (I'm using a TF-100 test kit.)

 

[chem geek]

If you add the right amount of chemicals, you don't need to test for borates since they won't go away and you'll start over again at your next refill. If you want to test for them, you need a separate test using Borates test strips. There isn't a reasonable drop-based test for Borates except a roll-your-own one, but the test strips are reasonable since it's not critical to be accurate. However, as I mentioned for a spa, I don't think you'll need the test strips. For a pool that's different because the water isn't changed and the borates can drop from water dilution over time.