pH down and testing

[jjdurrant]

Hi all, I am a constant battle with my pH and TA

I am using Leisure Time Spa Down and not MA. I understand I should be testing before I aerate as they naturally increase pH. The problem is, I need to run the pumps to mix the dry acid. How long do I wait before retesting each time? Thanks!

 

[AftonJeeper]

Have you considered switching to MA, it is cheaper and better for your spa. Pool School - Recommended Pool Chemicals

Below quote is from this link: How do I use Chlorine in my Spa (or pool)?)

OK, how do we adjust TA then? If TA is too low, you just add Baking Soda to raise it. However, if TA is high, it's little more involved. 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.

 

[jjdurrant]

I have used it.. it is just a pain to use and harmful for obvious reasons. Plus I hear it is not good for fiberglass so I do not want to risk it.

 

[jseyfert3]

How is it harmful? Anyway, so long as you don't spill directly on the spa material it it's not harmful to fiberglass or any other material used for spas. The sulfates in dry acid (PH Down) on the other hand are not good for heaters and other metal parts and will shorten their life. MA doesn't have this effect.

Can you provide more details on your specific issue? You said a battle between TA and pH. Are you trying to lower TA? What's your current readings?

While trying to lower TA, you would test your pH after aeration. The quote from the chlorine spa tutorial covers this, but essentially you aerate, test pH, if high, add acid and aerate, test pH, if high, add acid and aerate. You keep repeating until the pH stops climbing with a 30 minute aeration, which should happen around a TA of 50. Test the TA as you go along and start adding acid in smaller amounts as your TA approaches 50.

 

[jjdurrant]

Thanks.. I will switch back to MA then. I read a thread earlier that mentioned you should never test pH after aeration as that causes higher readings. Yes, I am trying to lower TA and pH. My fill water always causes the pH to spike when I add water which is generally a few inches each week. pH reading was 8.0 or higher. Not sure how over 8.0. After 4oz of Spa Down I am around 7.2. TA is 110 (was 150). I have the Taylor K-2006 kit. So I think I am on the right track here! I plan to get some Gentle Spa as well.

 

[Arobbert]

I add 4 to 6 gal water weekly in the winter (less in the summer) which increases my PH and AK. I add 2 to 5 ML muratic acid to the bucket used for filling. This keeps it in check. Found these handy droppers for measuring small amounts of acid. This is a lot easier than trying to measure tablespoons. A little bit of muratic acid goes a long way in my 200 gal tub!

OESS Glass Graduated Dropper Pipettes 5ml with Blue Silicone Caps Pk/3: Amazon.com: Industrial Scientific

 

[jseyfert3]

It does sound like you're on the right track. With a TA of 110 your pH will rise a lot with aeration. That's why the instruction thread says to lower TA to around 50 as that should keep pH rise in check.

You have to check pH after aeration because aeration causes a permanent pH rise, not a temporary one. So what good is testing before aeration if you are going to use aeration as a normal part of spa usage?