Water Balance And Maintenance

[Colorado Ice]

I have been maintaining a new hot tub for about one year. I have to adjust the ph and TA each time I check the water---once a week. The TA goes down to 75ppm and the ph goes above 8. Is it unusual to see fluctuations in ph and TA within a week? Can better stability be achieved?

Here's my specs.

I use a drop test type kit.

Hot tub: 300 gal

TA goal:120-150-ppm

CH:250ppm

ph goal: 7.2

Temp: 104F

Sanitizer: chlorine and mineral sanitizer(Nature2)

Spa shock and Enhanced shock 1-2 per week depending on use

CI

[chem geek]

The pH will tend to rise when the TA is too high. TA is a measure mostly of the bicarbonate in the water and the spa water is intentionally over-carbonated to have a pH buffer, but this is a SOURCE of rising pH due to carbon dioxide outgassing. Having the TA as low as 50 ppm reduces that pH rise. You can also use 50 ppm Borates such as from Proteam Gentle Spa for an additional pH buffer that is not a source of rising pH (you still need the TA to be low, howver).

Since it sounds like you are using Dichlor regularly for chlorine, it is a bit surprising that you still see the pH rise when the TA is at 80 ppm or below.

[Colorado Ice]

The pH will tend to rise when the TA is too high. TA is a measure mostly of the bicarbonate in the water and the spa water is intentionally over-carbonated to have a pH buffer, but this is a SOURCE of rising pH due to carbon dioxide outgassing. Having the TA as low as 50 ppm reduces that pH rise. You can also use 50 ppm Borates such as from Proteam Gentle Spa for an additional pH buffer that is not a source of rising pH (you still need the TA to be low, howver).

Since it sounds like you are using Dichlor regularly for chlorine, it is a bit surprising that you still see the pH rise when the TA is at 80 ppm or below.

[Colorado Ice]

Thanks. I have been adjusting the TA to 120ppm or higher by instruction from my dealer. I'll try keeping the tA lower and see what happens with the ph after a week.

CI

[quantumchromodynamics]

A TA of 120-150 is too high for a hot tub. A Calcium Hardness of 250 is also too high. I think that you would do better with a pH target range of 7.6 to 7.8 once you get your Calcium and TA down. It's important to avoid an excessive CSI (Calcite Saturation Index) as that could lead to scaling.

You can use ThePoolCalculator to calculate your Calcite Saturation Index. Under the section titled "Suggested Goal Levels" select "Traditional Spa".

For a Plastic/Fiberglass tub, the CSI should be kept slightly negative to avoid scaling. A pH of 7.6 to 7.8 will give you significantly better metal protection than a lower pH range.

You should not start with a preconceived target for TA. You need to find the correct TA for your tub. If the pH is constantly going too high, then your TA is too high. If your pH is constantly going too low, then your TA is too low. Your TA is just right when your pH stays in the target range.

You should not be using dichlor as your primary source of chlorine. Liquid chlorine or regular, unscented 6.00 % bleach is a much better choice. See the following links for more information.

Nitro's Approach To Water Maintenance

Dichlor/bleach Method In A Nutshell

[Kim Andi]

In my personal experience, it's better to have a little higher alkalinity - it will prevent folliculitis:

http://en.wikipedia.org/wiki/Folliculitis

[quantumchromodynamics]

In my personal experience, it's better to have a little higher alkalinity - it will prevent folliculitis:

http://en.wikipedia.org/wiki/Folliculitis

A higher TA will not prevent folliculitis