pH rise

[Tsinga]

I need help with my pH!

My water source is a private well.  The pH of my well water is about 7.4 at the kitchen sink.  When I fill the hot tub with cold water from the well and heat it to 104 F, the pH rises to well over 8.  This is before the addition of any chemicals.  I have added 7.5 ounces of 100% sodium bisulfate (acid) to the 300 gallon volume and the pH still remains over 8.  I know the acid is eating into the alkalinity so I really don’t want to keep adding acid.  I am just stumped by the rise in pH upon heating the water.  I’m using a brand new Taylor K-2106 test kit.  Any suggestions? 

[cranbiz]

Aeration will cause pH to rise.

Make sure you get your TA correct before trying to adjust the pH. 

[Tsinga]

Thanks for pointing out the aeration I had not considered that.  I believe my TA is within range.  I'm actually going to drain the hot tub, refill it, and check the pH and alkalinity before aerating or heating and compare it to my kitchen tap.  I will plan to add the sodium bromide, bromine tabs, and shock while aerating and heating.  

Please let me know if you have any other suggestions.

 

[CanadianSpaTech]

Do an Ahh-Some plumbing purge before draining. Remove anything in the plumbing that could effect water quality.

[Tsinga]

I added about a quart of vinegar and recirculated for 30 minutes before draining.  PH and alkalinity were ok at refill before heat, aeration, or any chemical addition.  Added the start up sodium bromide, broom tabs, and shock.  Headed out of town for a few days so I’ll recheck upon return.

 

Thanks for your help!

[Cusser]

Water without buffering chemicals is very susceptible to pH changes !!!

[Tsinga]

Hi,  

what chemical do you recommend to add for buffering?

 

thanks

[Cusser]

Sodium carbonate (soda ash) - sodium bicarbonate (common baking soda) mixture is generally used to pH buffer spas.  Sodium carbonate is used to raise pH, sodium bicarbonate added to bring pH down to appropriate level.

Unbuffered water near pH 7 is very susceptible to a smidge or a tad of added acidity or base.

[Tsinga]

My issue seems to be starting with a pH and alkalinity that are both within range and having the pH rise to over 8.0 as measured with a Taylor K2106 test kit.  If I add acid, the alkalinity drops but the pH remains high.  I suspect adding baking soda would only raise the pH.  I would like to lower the pH but keep the alkalinity up.  Is that possible?

[MrSkinny]

I have a similar issue that I am confused about. TA is always low at around 50 ppm and the pH is always too high at around 8.5. If I add Alk+ it raises the pH too and if I add pH- it also lowers the TA. How am I supposed to get both of these in range?

[CanadianSpaTech]

https://www.poolspaforum.com/forum/index.php?/forum/13-hot-tub-water-chemistry/

[Tsinga]

It seems to me that you need to either pick the alkalinity or the pH, but not both.  I can’t seem to get both in range except on the initial fill, before chemical addition, heat, or aeration.  I am choosing to watch the alkalinity and letting the pH rise to over 8.0.

 

Anyone doing the same?

[CanadianSpaTech]

Follow the link I posted above and ask chemical related questions there for best results.