Alkalinity

digger0713

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Sep 8, 2015
26
Brownstown/Michigan
Hi Everyone. I have been reading as many posts on this subject as I can, as well as pool school and I still don't quite have an answer. I have a Viking Royale Hot Tub and every time I think I have my alkalinity in line, my PH drifts high into the 8.2 range, so I lower it with muriatic acid to 7.2 and try to let it raise naturally through aeration with my jets and waterfall. I feel like it keeps raising way too fast on me. I try to target an alkalinity of 100, to be in the middle of the 80-120 range like everything says to be. Then I read posts on here about people recommending keeping my alkalinity in the 50-60 range. Where should I keep it so I can stop this heavy PH swing I'm experiencing. My alkalinity is currently at 55 and I'm afraid to raise it to 100 because I know it's going to raise my PH and I don't want it to go off scale. I don't want to have to always adjust my PH daily after using the hot tub because the aeration takes it too high. What am I doing wrong? Here are my most recent numbers from testing with a Taylor K-2006 kit. Thank you for any clarity and help you can provide.
Bromine: 4.0
PH: 7.4
TA: 55
CH: 175
CYA: 40
 

jseyfert3

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How do you get a reading of 55 from a K-2006? The lowest resolution is 10 ppm per drop, so a result of 55 isn’t valid.

The 80-120 is a generic manufacturer recommendation, not a TFP one. As you’ve read taking the TA down to 50 is perfectly fine, and usually required, for a hot tub. The lower the TA, then slower the pH rise is over time.
 
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Mdragger88

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Like @jseyfert3 stated leave the TA alone & the roller coaster ride will end. Only add baking soda if it gets to 40.
 

jseyfert3

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Also why do u have cya if you’re running bromine?
Good one, I missed that. Looking back I also see they are running a K-2006. @digger0713 are you scaling the result from the K-2006 FC test with the appropriate bromine conversion factor?
 

digger0713

Active member
Sep 8, 2015
26
Brownstown/Michigan
How do you get a reading of 55 from a K-2006? The lowest resolution is 10 ppm per drop, so a result of 55 isn’t valid.
When I do my drop test, the sample doesn't turn completely red at 50 ppm, but at 60 ppm it goes bright red, so I just split the difference and call it 55. Maybe I'm not doing that correctly, but I figured it was better than under or over shooting it.
Also why do u have cya if you’re running bromine?
I know CYA is probably a moot test to run for my tub considering it is covered when not in use so the sun can't really destroy it very quickly, but I do add a small amount of hot tub chlorine powder weekly to regenerate the bromide base and take it to shock level. I know the chlorine powder will raise CYA in the tub and I monitor it to make sure it doesn't get too high and out of control.
Looking back I also see they are running a K-2006. @digger0713 are you scaling the result from the K-2006 FC test with the appropriate bromine conversion factor?
For my bromine test, I use the FAS-DPD powder test with the bromine reagent. I have the speed stir and in my 25ml tube, it says one drop equates to .5 ppm of bromine. I don't use the double test tube thing in the kit for that. I like my speed stir for bromine, alkalinity, and hardness.
I appreciate the comments and advice. I'll keep my TA around 50 and hopefully the PH swing will slow down. When the PH gets up to around 8.0 due to aeration, should I use muriatic acid to lower it back down to 7.2 and then make sure my alkalinity is at 50, or should I just add enough muriatic acid to lower the PH down to around 7.5? I'll do my best to keep the alkalinity around 50. I know adding acid lowers the alkalinity so I'll monitor it whenever I add acid.
 
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jseyfert3

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When I do my drop test, the sample doesn't turn completely red at 50 ppm, but at 60 ppm it goes bright red, so I just split the difference and call it 55. Maybe I'm not doing that correctly, but I figured it was better than under or over shooting it.
It’s unclear in the directions from Taylor, but in the Extended Test Kit directions here (which have been gathered from various sources including additional info from Taylor) the instructions are to test until there is no further color change. The last drop that causes no further color change does not count, but everything up to it does. So your TA is at least 60 right now. Total Alkalinity - Trouble Free Pool

I know CYA is probably a moot test to run for my tub considering it is covered when not in use so the sun can't really destroy it very quickly, but I do add a small amount of hot tub chlorine powder weekly to regenerate the bromide base and take it to shock level. I know the chlorine powder will raise CYA in the tub and I monitor it to make sure it doesn't get too high and out of control.
CYA is moot when running bromine, is has no effect on bromine for buffering harshness or UV breakdown. This is actually why nobody really uses bromine pools, with the exception of some indoor pools, as unlike CYA for chlorine there’s nothing that keeps bromine from breaking down in UV.

This is also why the K-2005, the bromine test kit, does not come with a CYA test.

For my bromine test, I use the FAS-DPD powder test with the bromine reagent. I have the speed stir and in my 25ml tube, it says one drop equates to .5 ppm of bromine. I don't use the double test tube thing in the kit for that. I like my speed stir for bromine, alkalinity, and hardness.
Ah, good. Just checking. It is possible to use the FC reagent to test bromine, but you have to scale the result. If testing with the actual bromine reagent then follow those directions, as you are.

I appreciate the comments and advice. I'll keep my TA around 50 and hopefully the PH swing will slow down. When the PH gets up to around 8.0 due to aeration, should I use muriatic acid to lower it back down to 7.2 and then make sure my alkalinity is at 50, or should I just add enough muriatic acid to lower the PH down to around 7.5? I'll do my best to keep the alkalinity around 50. I know adding acid lowers the alkalinity so I'll monitor it whenever I add acid.
Usually when I get down to 50-60 ppm of TA I will target 7.5-7.6 when I add acid, instead of 7.2. A lower TA will result in lower pH rise, but a lowe pH will always result in a faster pH rise than a higher pH.

I have at times gone as low as 40 ppm TA, but that’s probably the absolute lowest you’d ever want to go. The lower the TA, the more a given amount of acid will drop the pH. Poolmath corrects for this in pH calculations pretty good, but if you do get the pH steady at a lower TA don’t forget dichlor is acidic and adding it can lower the pH.
 

JoyfulNoise

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You should consider adding borates to your hot tub as they will help moderate the pH rise. Also, stop dropping the pH so low. Target a pH of 7.6 and then don’t lower it again until it goes above 7.8. Don’t run your air jets unless you absolutely have to. Some tubs allow you to close off the air intake; if that is an option on your hot tub then close the air intake until you need to use it.
 

digger0713

Active member
Sep 8, 2015
26
Brownstown/Michigan
Thank you everyone for the advice. I'm still relatively new to hot tub maintenance. I have my pool down to a science and it goes great all summer. This hot tub is a little trickier, but I'm slowing beginning to understand it better. I'll make sure to target the 50 alkalinity and when my PH gets to 7.8 or above, I'll target it back down to 7.5-7.6. I can close off my air jets and I always close them unless I'm using the tub. I am interested in using borates, but I checked for them online and most websites I checked said they were sold out. I'll keep a look out for them. Thanks!
 

mknauss

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I am interested in using borates, but I checked for them online and most websites I checked said they were sold out.
Check out Dudadiesel. Get granulated Boric Acid.
 

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jseyfert3

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Borax can also be used, but requires the addition of acid to counter the pH rise. This usually isn’t the best way for pools cause you need so much acid whereas boric acid is much more pH neutral, but for spas it’s probably the way to go since Borax is easily obtainable at local stores in the laundry aisle, and the acid required is not much.
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