PH keeps rising

[jmcdtucson]

I have a new-to-me small hot tub. I'm using bromine. All seems to be going OK following the 3-step process outlined in the sticky.
However, I can't maintain PH - every day it's back to 8 or above.
I add PH down and the PH drops but then rises again by the next day.
TA started over 70 and now is down to 20.
Not sure what I should do. I have some Gentle Spa on the way to hopefully help, but I'm not sure that will help.
I have the recommended Taylor test kit.
Any ideas? Thanks!

 

[Texas Splash]

How often do you use the tub? Frequency of use would impact pH. Any chance your pH testing reagent is old or going bad?

 

[Mdragger88]

Are u testing the ph right before use or after?
If its after, the ph may be high immediately due to the jet action but it may settle down a little. Try testing ph when the water is still.
Also - Ta of 20 is on the low side -
40- 50 is about as low as u wanna go.
You may be experiencing ph bounce because of this.
Gentle spa is not ph neutral & may not do what u think it will
It is Sodium tetraborate pentahydrate
Use PoolMath effects of adding to see it’s potential effects you will need to counteract.

Boric acid is a more ph neutral solution.
As well as being more economical.


One other thought-
If your sanitizer level is quite high you may be getting a falsely high ph reading as well.
This holds true for fc above 10ppm
Not sure how high bromine needs to be to affect this.

 

[jmcdtucson]

I've been using the spa daily.
I measure mid-day, long before i use it in the evening.
The test kit is brand new.
I've been maintaining bromine levels between 1 and 6 (challenging to keep it stable.)
I'll keep an eye on the Gentle Spa. Now that I read more, there seems to be lots of conflicting info on Gentle Spa and maybe multiple formulations over the years: some Ph neutral, some not. I will watch out for that.
Thanks for ideas. For now have added Baking Soda to get the TA back into 50ppm range. Maybe I will just have to continuously balance. I'm familiar with pools but not spas.

 

[Mdragger88]

The ph rise in spas is inevitable due to all the aeration & will always need adjusting.
Adding borates can help but it doesn’t eliminate the need for acid. One other thing to consider (with borates or without) is to only lower ph to around 7.5-7.6 so you don’t drop ta as rapidly.
There are several “proprietary, trade secret” ingredients in the gentle spa so its hard to know what else you’re getting in addition to the Sodium tetraborate pentahydrate. I’m not a fan of adding unknown ingredients to a pool or hot tub as it’s uncertain how they will affect the chemistry. This is especially true if you’re already having difficulties- it just makes things more complicated.
We know exactly what straight boric acid will do & can test to confirm the results.