Can't lower PH for decontamination

[Figi4]

I am trying to do the decontamination process from Nitro.  I have already done the enzyme part and dumped that. Now it's filled and I am trying to balance it to the TA of 80 and PH of 7.2.

I've got the TA at 80 but nothing is getting the PH down.  I just bought the test kit K-2106.  The PH is showing at the highest level, and I only have to add 2 drops and it turns pink.  So I check the book and for my 350 gallon spa I calculate that I need .63875 oz of muratic acid (18.89 ml)  I do that and come back a few hours later or the next morning and test again.  It gives me the same thing - high PH and 2 drops turns it pink.  I've done this 4 times now.

The only thing differently that I've done is that there is no filter.  I accidentally missed the part of throwing the filter into the spa when I put the enzyme in and have a new one ordered.  I didn't think it would be a good idea to put the dirty one back in.  (The spa set with water for over a year - covered on a covered porch.  Water was still crystal clear.)

Any ideas on what I should do?

[waterbear]

 

What is your sanitizer in PPM?

 

16 hours ago, Figi4 said:

The PH is showing at the highest level, and I only have to add 2 drops and it turns pink.

"Highest level: tells us nothing, What is the actual number. You added 2 drops of which reagent and it turns pink? Are you talking about the acid demand test? Once again, "turns' pink" tells us nothing. We need the actual test result numbers.

First thing to do is post a FULL set of test results done with your test kit (Total Bromine, pH, TA, CH). Don't worry about the acid demand test now.

I will add this, there is a strong possibility that your TA is too high at 80 ppm since you are seeing a pH rise that is possibly from outgassing of CO2 but don't do anything until you have posted the test results in case something else is going on.

Read these:

https://www.poolspaforum.com/forum/index.php?/topic/52522-some-truths-about-ph-and-ta/

https://www.poolspaforum.com/forum/index.php?/topic/28846-lowering-total-alkalinity-howto/

 

[Figi4]

Ok ill get those. But real quick, I don't have sanitizer in it. Reading step 4 sounds like the TA & PH need to be done before adding the sanitizer??

[Figi4]

 

PH: 8.0 

TA: 80ppm

Bromine: have not added any

CH: 120ppm

Water Temp:  74F

Spa is off as of now and is uncovered, but sitting on a covered porch.  

When doing the testing:

Using the K-2106 testing kit and measuring the pH, it states to add 5 drops of R-0004 and to cap and mix. The resulting color matches the highest level, which shows 8.0.  It may be higher but I am not sure since my kit only shows up to the 8.0.  Now when I use a dip strip it shows the range to be close to the 7.2 color, but I know that y'all say not to rely on those so that is why I bought the kit.  I can see why.

When then adding the 2 drops of the R-0005, it turns the color that I am shooting for which is 7.2.

When check the TA, I add the 5 drops of R-0008 like it states and the water turns green and then when I start adding the R-0009, the color changes to pink on the 8th drop, which suggests that TA is 80ppm.

I do not have any bromide/bromine in it as I was under the impression that is not needed for this part, just when refilling after I've done the decontamination.  If it does I'll need to order some more bromide as they do not sell those near me and I only have enough for one fill.

Maybe I am misunderstanding Step 4 and that's why I cannot get the PH to come down?

[waterbear]

On 5/27/2021 at 11:57 AM, Figi4 said:

Reading step 4 sounds like the TA & PH need to be done before adding the sanitizer??

No but sanitizer cannot be at shock levels (needs to be under 10 ppm for both chlorine and bromine) since high sanitizer levels interfere with both the pH and TA tests. NEVER test or adjust TA or pH when sanitizer is high. Your readings will either be inaccurate or unreadable (colors not on pH comparator, particularly with bromine)

[waterbear]

On 5/27/2021 at 3:05 PM, Figi4 said:

When then adding the 2 drops of the R-0005, it turns the color that I am shooting for which is 7.2

(a) you then need to consult the book that came with your kit to determine how much acid is needed to drop the pH to 7.2 based on the number of drops of acid demand reagent. Now check your TA. IF it is not 50 to 70 ppm start aeration until the pH rises to 8.0.do another acid demand test (b). Repeat from (a) to (b) until the TA is in the range of 50 to 70 ppm. If you want you can aerate to bring the pH up to around 7.6 to 7.8 but ;personally I wouldn't bother since the pH will rise on its own. Maintain the pH around 7.8 with bromine for the best pH stability.

 

On 5/27/2021 at 3:05 PM, Figi4 said:

when I start adding the R-0009, the color changes to pink on the 8th drop, which suggests that TA is 80ppm

When doing TA and CH titrations good practice is to add drops until the last drop added produces NO FURTHER COLOR CHANGE and then don't count that last drop. To use your example, you add 8 drops and then add a 9th drop that does not produce any further change of the red color. Don't count that 9th drop so you would be at 80 ppm TA.

On 5/27/2021 at 3:05 PM, Figi4 said:

do not have any bromide/bromine in it as I was under the impression that is not needed for this part, just when refilling after I've done the decontamination.

Decontamination is done with chlorine (use bleach btw) You don't need sodium bromine or bromine tabs for this step.

 

On 5/27/2021 at 3:05 PM, Figi4 said:

Maybe I am misunderstanding Step 4 and that's why I cannot get the PH to come down

lo lower pH you add acid. The pH will come down. That's how it work.  You have to add enough acid to overcome the buffering effect of the carbonic acid/bicarbonate buffer we call TA.

Lowering TA is done by lowering your pH, which lowers the TA, then aerating to raise pH WITHOUT RAISING TA by outgassing carbon dioxide so it cannot reform bicarbonate (TA). It is a process that takes multiple times lowering pH and then aerating before you see results. The act of adding acid lowers TA because it converts bicarbonate into carbonic acid (for our purposes this is the same as carbon dioxide dissolved in the water). When TA is high it takes more acid to lower the pH from the same starting point to the same endpoint (i.e. from 7.8 to 7.2) than it does when the TA is low. Also the effect of this buffer system is to cause pH to rise. This can be minimized by keeping the TA low (but not too low so pH doesn't "crash" and this is determined by the products you are using for sanitation and shock), NOT putting the pH too low (7.7 -7.8 and lower it when it hits 8.0 no lower than 7.6), and adding 30-50 ppm borate with either a commercial borate product for spas and/or pools or by using boric acid (which will cause a slight pH drop that I usually ignore since the pH WILL rise) or borax- sodium tetraborate decahydrate  (20 Mule Team Borax) or pentahydrate and the the necessary acid to neutralize the pH increase from the borax. some commercial borate products are pH neutral since they are a mixture of boric acid and the pentahydrate form of borax while others are just sodium tetraborate pentahydrate and the instructions tell you that you also need to add acid (either muriatic or dry) when dosing.

[newtubuser413]

This isn't even my thread, but just want to say really appreciate your attentiveness to answering other people's questions @waterbear  

[Figi4]

Thanks @waterbear. I've been sticking to it and finally got the water to balance to finish the decontamination process.  We cleaned and refilled it and now in the process of balancing it to add the bromine as suggested in the 3 Step process.  It's going much better now that I understand it more.  It also looks great to not see the brown scum building up on the side walls.  I really worried that would never fully stop and that it was just a lost cause without multiple decontaminations, which I wasn't looking forward to do.