PH jumps above 8

[Clarence S]

I have a new Marquis Spa.  365 gallon.  I have the water balanced.  I keep the water level just above the jets.  Any higher then the level is too high when 2 people are in the spa.  Because of this I have to add water due to evaporation every few days.  Then the PH jumps high.  It has been as high as 8.8!  I use 3 step Bromine.  Currently I'm at TA = 50, this rarely changes, Bromine 7.5, PH 7.3, and CH = 170.  I use a filter when adding tap water.  The CH was very low on start-up ( = 40)

[Cusser]

Did you add any buffer like baking soda (sodium bicarbonate, NaHCO3) ???  Without a buffer pH can swing quickly.  A bicarbonate-carbonate buffer helps keep pH where it should be.

[Clarence S]

I did not.  I'll try it.  But that will raise TA in my understanding 

[waterbear]

I am moving your post to the Hot Tub Water Chemistry section of the forum.

How are you testing? Are you using DPD for testing bromine? (I want to eliminate a false high pH reading because of DPD bleachout) What is the pH and TA of your fill water. Main cause of pH rise is outgassing of CO2 had this is directly related to how low you place the pH and how high the TA is. With a TA of 50 you should have minimal outgassing but if you are lowering your pH below 7.6 this will cause pH to rise faster.

These posts will explain what is happening, read them:

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/

[waterbear]

13 hours ago, Cusser said:

Without a buffer pH can swing quickly.  A bicarbonate-carbonate buffer helps keep pH where it should be.

Not really. We are both well versed in chemistry so I don't want to go into too much depth here, but in a nutshell the carbonic acid/bicarbonate buffer will generally cause pH to rise as the carbonation is lost from outgassing. Henry's Law says that CO2 will off-gas until it reaches equilibrium with the air above the pool or spa. This the pH ceiling and it is around 8.2 for recreational water. If the TA is higher then there will be more carbonic acid at a given pH as the buffer reaches equilibrium and there is then more CO2 to outgas along with a faster pH rise as opposed to  slower outgassing and slower pH rise at a lower TA since the overall carbonation of the water is lower.

FWIW, adding a secondary boric acid/borate buffer WILL slow the rise of pH which the main reason to add 50 ppm borate.

[Clarence S]

Got it.  I use Taylor to test.  I do not know the PH of my tap water.  My tub PH is stable around 7.4.  I did raise the TA to 80

[waterbear]

1 hour ago, Clarence S said:

I use Taylor to test

which kit?

1 hour ago, Clarence S said:

I do not know the PH of my tap water.

test it. it might be the culprit.

1 hour ago, Clarence S said:

I did raise the TA to 80

This can caused the pH to rise more rapidly.

When you add fill water do you add any other chemicals to the tub or shock the the tub? If you are testing bromine with DPD (comparator with shades of red) and not FAS-DPD (drop counting testing with color change from red to colorless) or OTO (comparator with shades of yellow) it is possible that your test is bleaching out because of high sanitizer and reading much lower than it actually is. High sanitizer will cause pH to read high when it's actually low because the high sanitizer converts the phenol red pH indicator into bromophenol red (which has the same color changes but for a much lower pH range(. This is why I asked which Taylor kit you are using since they sell kits with all 3 methods of testing sanitizer.

[Clarence S]

I use the Taylor test kit K 2106.   I also have the Crystal Water monitor.  Both readings agree.  Also, I been using chlorine shock.  Can I switch to MPS without draining the tub?

[waterbear]

12 hours ago, Clarence S said:

Can I switch to MPS without draining the tub?

Yes but I would not r recommend it. You could use both MPS and chlorine at the same time if you wanted to. MPS is a known sensitizer and will add sulfate to your water. it is also more expensive. IMHO, the only reasons to use MPS is with a chlorine tub or indoor pool that has persistent CC over 1 ppm or with a sliver nitrate cartridge such as Nature2 in a hot tub (silver ions and MPS become an EPA sanitizer in hot water). There is no known advantage to using MPS to activate bromine.

[waterbear]

12 hours ago, Clarence S said:

I use the Taylor test kit K 2106

This uses FAS-DPD which is the preferred method of testing sanitizer and not subject to bleachout. I would look to your fill water at the culprit.

[Clarence S]

Alot of info.  I love this site

[Clarence S]

9 hours ago, waterbear said:

This uses FAS-DPD which is the preferred method of testing sanitizer and not subject to bleachout. I would look to your fill water at the culprit.

I suspect,  by my initial tests, with a filter the fill water has a PH of 8.4, TA of 40, CH of 40

9 hours ago, waterbear said:

Yes but I would not r recommend it. You could use both MPS and chlorine at the same time if you wanted to. MPS is a known sensitizer and will add sulfate to your water. it is also more expensive. IMHO, the only reasons to use MPS is with a chlorine tub or indoor pool that has persistent CC over 1 ppm or with a sliver nitrate cartridge such as Nature2 in a hot tub (silver ions and MPS become an EPA sanitizer in hot water). There is no known advantage to using MPS to activate bromine.

Yes.  MPS is expensive.  But the Frog In-Line came with MPS,  which I havent used.  This tub does have a Frog mineral cartridge.

[waterbear]

12 hours ago, Clarence S said:

his tub does have a Frog mineral cartridge.

which you neglected to say. In that case you are not doing 3 step bromine. You are using a silver/bromine system and I would recommend following the instructions for the Frog or stop using the mineral cartridge and use 3 step bromine (my suggestion). I am not a fan of mineral cartridges since the low sanitizer levels that are often recommended can lead to water problems.

12 hours ago, Clarence S said:

the fill water has a PH of 8.4

 

On 9/26/2023 at 2:21 AM, Clarence S said:

I have to add water due to evaporation every few days.  Then the PH jumps high

You have answered your own initial question. Your fill water has a high pH and, depending how much you are adding, will raise the pH. My suggestion is to lower the pH after adding fill water and keep your TA around 60 ppm and add 50 ppm borate to create a secondary boric acid/borate buffer system (get some LaMotte borate test strips or  Industrial Test Systems  Poolcheck Borate test strips for testing borate. Stay away from Hach, Taylor, and AquaCheck, their color changes are very difficult to read and very close together.) Don't lower your pH below 7.6 and don't worry about lowering it until it climbs above 8.0. Sweet spot for pH when using borate is 7.8 to 7.9.

Borate is compatible with mineral cartridges. There are commercial borate products such as Proteam Gentle Spa, Phoenix Serena Spa Borate Plus, Proteam Supreme Plus (for pools but can be used in spas) , or Bioguard Optimizer Plus (for pools but can be used in spas) , or you can use granular boric acid from online retailers as Amazon, DudaDielel, or the Chemistry Store. You want to maintain a 30 t0 50 ppm range. It is lost by splash out so you will need to test and add more when you add new fill water. One advantage to using boric acid is that when you add more to compensate for the fill water it will slightly lower the pH,. You still might need to add some acid to get the pH in line.

4 oz. of boric acid per 100 gallons will get you to 50 ppm (3.8's  oz by weight or 4.1 oz by volume if you want to get exact but it's not necessary, 4 oz either way is close enough. That's half a cup.) 1.5 tablespoons per 100 gallons will raise the borate level approx. 10 ppm for when you need to bump it up after refilling the splash out. If you are losing water from evaporation you should not need to add more since it's not lost by evaporation.

As I said early, you want to maintain the borate level between 30-50 ppm so you don't need to add more until it drops to 30 ppm then add enough to bring it back to around 50 ppm.

If you decide to use a commercial borate product for pool or spas follow the directions.

 

 

[Clarence S]

On 10/2/2023 at 11:45 AM, waterbear said:

which you neglected to say. In that case you are not doing 3 step bromine. You are using a silver/bromine system and I would recommend following the instructions for the Frog or stop using the mineral cartridge and use 3 step bromine (my suggestion). I am not a fan of mineral cartridges since the low sanitizer levels that are often recommended can lead to water problems.

 

You have answered your own initial question. Your fill water has a high pH and, depending how much you are adding, will raise the pH. My suggestion is to lower the pH after adding fill water and keep your TA around 60 ppm and add 50 ppm borate to create a secondary boric acid/borate buffer system (get some LaMotte borate test strips or  Industrial Test Systems  Poolcheck Borate test strips for testing borate. Stay away from Hach, Taylor, and AquaCheck, their color changes are very difficult to read and very close together.) Don't lower your pH below 7.6 and don't worry about lowering it until it climbs above 8.0. Sweet spot for pH when using borate is 7.8 to 7.9.

Borate is compatible with mineral cartridges. There are commercial borate products such as Proteam Gentle Spa, Phoenix Serena Spa Borate Plus, Proteam Supreme Plus (for pools but can be used in spas) , or Bioguard Optimizer Plus (for pools but can be used in spas) , or you can use granular boric acid from online retailers as Amazon, DudaDielel, or the Chemistry Store. You want to maintain a 30 t0 50 ppm range. It is lost by splash out so you will need to test and add more when you add new fill water. One advantage to using boric acid is that when you add more to compensate for the fill water it will slightly lower the pH,. You still might need to add some acid to get the pH in line.

4 oz. of boric acid per 100 gallons will get you to 50 ppm (3.8's  oz by weight or 4.1 oz by volume if you want to get exact but it's not necessary, 4 oz either way is close enough. That's half a cup.) 1.5 tablespoons per 100 gallons will raise the borate level approx. 10 ppm for when you need to bump it up after refilling the splash out. If you are losing water from evaporation you should not need to add more since it's not lost by evaporation.

As I said early, you want to maintain the borate level between 30-50 ppm so you don't need to add more until it drops to 30 ppm then add enough to bring it back to around 50 ppm.

If you decide to use a commercial borate product for pool or spas follow the directions.

 

 

Got it.  My new PH target is 7.8 or so.  Just seems so easy to go over 8.  I will order the borate.  I'm guessing no Borax!?

[waterbear]

11 hours ago, Clarence S said:

I'm guessing no Borax!?

You can use borax but it will raise the pH so you will also need to add acid with it which complicates the process. I used to use borax decahydrate from from the grocery store and muriatic acid but using boric acid is much easier since you don't really need to compensate for the pH as long as your starting pH is not below about 7.4. Only drawback it it's a bit more expensive than borax and acid but it's still WAY less expensive than the commercial products (which are basically a mixture of boric acid and borax pentahydrate to create a pH neutral product. The pH lowering effect from boric acid is negligible but the pH rise from straight borax, either pentahydrate or decahydrate is quite a bit. The only difference between the pentahydrate and decahydrate forms of borax is one had 5 water molecues attaches andt the other 10 so the pentahydrate needs less by weight to achieve the same level of borate in the water. The first commercial borate products such as Proteam Supreme and BIoguard Optimizer for pools and spas was just the pentadydrate form and required the addition of acid. Newer formulation (Supreme Plus, Optimizer Plus) are pH neutral because they contain both the pentahydrate form of borax and boric acid.

If you still want to use borax let me know and I will calculate dosing.

[Clarence S]

10 hours ago, waterbear said:

You can use borax but it will raise the pH so you will also need to add acid with it which complicates the process. I used to use borax decahydrate from from the grocery store and muriatic acid but using boric acid is much easier since you don't really need to compensate for the pH as long as your starting pH is not below about 7.4. Only drawback it it's a bit more expensive than borax and acid but it's still WAY less expensive than the commercial products (which are basically a mixture of boric acid and borax pentahydrate to create a pH neutral product. The pH lowering effect from boric acid is negligible but the pH rise from straight borax, either pentahydrate or decahydrate is quite a bit. The only difference between the pentahydrate and decahydrate forms of borax is one had 5 water molecues attaches andt the other 10 so the pentahydrate needs less by weight to achieve the same level of borate in the water. The first commercial borate products such as Proteam Supreme and BIoguard Optimizer for pools and spas was just the pentadydrate form and required the addition of acid. Newer formulation (Supreme Plus, Optimizer Plus) are pH neutral because they contain both the pentahydrate form of borax and boric acid.

If you still want to use borax let me know and I will calculate dosing.

Thanks