pH will not come down

[m2kw6s]

Greetings,

I'm having a problem getting my hot tub water chemistry to balance. I've spoken to my dealer and read the TFP guidance, and I've been diligent with my record keeping.

I hope someone can pinpoint what I'm doing wrong. The short version is that I cannot get my pH to come down from > 8.2 into the ideal range.

The long version is detailed in the table below with notes about what I see going on and what I'm attempting to do each time.

I'm only measuring pH when Alkalinity is between 80-120. I understand that "Spa Down" lowers pH at a greater rate than Alkalinity, but I don't understand why I'm never getting into the ideal pH range before the Alkalinity drops out of range. Especially since the Taylor Acid Demand test seems to come in at reasonable number of drops. I'm adding the correlating amount of acid to get the pH to respond with no movement.

I've used test strips to compare my Alk and pH readings, so I think my test kit is fine. None of my Taylor chemicals have expired.

Any suggestions?

Thank you in advance.

 

[ajw22]

M2, welcome to TFP.

What is the TA & pH of your fill water you are starting with?

I would not raise my TA to 80 before testing the pH. pH is the important controlling value. Raise the TA to get the pH up into the 7's. Whatever TA that takes is fine. Go slow with small does to get your pH into the 7's. Manage the pH first and not the TA.

 

[m2kw6s]

Thank you Allen...

The fill water is TA 30-40 and ph is > 8.2.

My dealer's advice was to work on the TA first, then dial in the pH. Happy to switch my approach. Should I start with fresh water, or keep going with what I've got?

How long should I wait between adding a "dose" of chemicals and re-testing and potentially re-dosing? 24 hours?

Thanks,
Mark

 

[mknauss]

That TA with that pH is a challenge. I am going to summon @JoyfulNoise for his input.

 

[Flying Tivo]

Are you sure of your FC?? Can you double check with a FAS-DPD?
Just a tought!
Felipe

 

[ajw22]

I would start with fresh water. With pH 8.2 and TA of 30-40, raising the TA just added to a higher pH problem. And we don't know where your pH is right now.

PH Meters would help you know where your pH is with that fill water situation since a meter can read a wider range then the color test.

I would take your fill water and fill a 5 gallon bucket. That is about 1.6% of your spa volume. Weigh small amounts of pH up and find out what it takes to get the pH in the bucket into the 7's. It may take some trial and error and you may overshoot a few times. Also see what happens to the TA when the pH gets into the 7's.

Then 60X that amount is about what you need for 300 gallons. I would sneak up on it by putting 1/2 in your spa, then 1/2 of what is remaining (1/4), etc. until you get pH into the 7's. You just need to run the pump and wait about 30 minutes between doses.

I would drain the spa and start with fresh water; do the 5 gallon bucket test; figure out how much pH down will be required; then do a 1/2 dose every 30 minutes testing pH and TA along the way. Log what happens and let's see.

 

[splashpad]

The fill water is TA 30-40 and ph is > 8.2.

Dropping some more ideas:
Have you let straight tap water sit for 12-24hrs (a glass, a bucket, etc), to "gas off", it's not unusual for tap water to have high PH due to being pressurized in pipes. (usually this is more of an issue with aquariums)

Also assuming your spa is fiberglass?

Have you run a full set of tests? Can you share the results, please?

 

[JoyfulNoise]

Can you confirm the test reagents numbers you are using along with the comparator block you are using for pH and TA?

It’s is highly unusual to have fill water with that low a TA and such a high pH. And, since you are adding acid and not seeing the pH drop, I suspect there is some kind of testing error here. Your acid demand drops are just HCl and those seem to be moving the pH in the right direction.

Also, this is suggestion, but you should stop buying those overpriced Leisure Time chemicals. The Spa Up is nothing more than baking soda which you can get at any supermarket for a dollar per pound and dry acid is really not good as you will build up sulfates in your tub water and that causes excessive corrosion of the Hester element. Simply buy some muriatic acid from the hardware store and use that. It’s a lot cheaper. You can also buy the 15% “low fume” type MA so it’s easier to use.

 

[m2kw6s]

Felipe - I'm just adding a bit of DiChlor every few days to keep things clear. I don't have a FAS-DPD test, but I'll consider that.

Allen - I did just order a pH Meter to get a better idea how far above 8.2 I am. Thank you for the specifics on the timing and the 5-gallon bucket method. I'll do some research and see if my current digital scale is precise enough for that.

splashpad - I will try the "gas off" as well. The hot tub is acrylic.

Matt (JoyfulNoise) - Here are the test reagent numbers and Comparator block info.

• Taylor Kit K-1004
  • pH Test / Acid Demand
    • pH Indicator Solution R-0014
    • Acid Demand Reagent R-0015
    • Comparator Model 9782
  • Alkalinity Test
    • Thiosulfate N/10 R-0007
    • Total Alkalinity Indicator R-0008
    • Sulfuric Acid .12N R-0009

A couple containers of Leisure Time chemicals were provided by the dealer when the spa was delivered, so I will definitely follow your advice on restocking.

Thanks to all of you for chiming in.

 

[Flying Tivo]

The one thing you should consider is that if FC is above 10 your PH will always read high. Now that you say that you are adding dichlor without measuring the addition, my best guess is that your FC is way higher than 10. Please stop chasing your ph until you get a FASDPD measurement of FC. You will only waste money.

Felipe

 

[ant 83]

In your chart there, I see you don't let alk drop below 80 before adding more buffer.

Aim for an alk of about 50, then see how PH does.

Keep in mind that dichlor works as an acid. You could just chlorinate with that, and put the alk test kit away for a while. Once your PH falls in line, then switch to bleach.

The reason they tell you to keep alk at 80-100 is cause they are worried about your ph falling too low, and dissolving your heater, which they will then have to replace under warranty. This happens when folks only use dichlor and unreliable test strips to test ph. Dichlor is acidic and so PH will drop over time from using it. Low PH isn't a problem for folks that use bleach, so an ALK level lower than 80 isn't a problem.

So, you can drop your Ph with dichlor, then switch to bleach when your PH gets to 7.5.

Bleach makes PH rise, but by a very small amount that takes weeks to amount to anything you can test for.

If your fill water is truly at 30, you may need to add some buffer after a fresh water fill. Let PH be your guide.

 

[ajw22]

Buy pH 7 standard solution to regularly calibrate your pH meter.

I suggested starting with fill water in the bucket test to eliminate any dichlor effects.