Hot tub start up

[Mamamartini]

Good morning! So, we recently sold our home with the in ground pool, but our new home has a hot tub. If I give the numbers, can anyone tell me what chemicals I need? We will be using the chlorine method. The previous owners only have Clorox xtra blue 6-in-1 granules on hand. Can I use that to get my CYA up to 30, or does it need to be dichlor? Ok, for the numbers:

FC = .5
CC = 0
PH = 7.8
TA = 40-50**
CH = 75

**when I tested the TA, it turned red at 40, but noticeably more red at 50 - how do I interpret that?

I'm confused about how to increase the TA, while decreasing the PH. These numbers are pure tap water after draining (flushing lines with Ahhsome), cleaning and refilling.

Thank you!!!

 

[JoyfulNoise]

Your TA is 50ppm. You stop counting when the red color stops changing.

Your fill water is fine but is it two water OR water from a softener?

DO NOT use the 6-in-1 garbage as it likely has copper in it. Go and buy just pure dichlor granules.

I’d also add borates (boric acid from Duda Diesel or 20 Mule Team borax) to the water. Boric acid can be added directly with no adjustments. Borax requires acid to offset the pH it creates. See the borates section in Pool School.

 

[Mamamartini]

The water is city water with no softening.

- should I increase the calcium to 100?
- should I add muriatic acid to decrease my PH?

Thank you!

 

[pooldv]

Yes, raise CH to 125 to reduce foaming. And also yes to using muriatic acid to lower pH.

More here about pool chems, Pool School - Recommended Pool Chemicals

More here about spa chemistry, How do I use Chlorine in my Spa (or pool)?

And +2 to not using anything that is "blue". You do not want to try to deal with copper stains. There are millions, (if not billions ), of threads here about how difficult it is to deal with copper stains.

 

[Mamamartini]

Won't the muriatic acid lower my TA?

 

[JoyfulNoise]

You only need to lower your pH down to 7.6. The amount of acid needed will be quite small and the TA won’t drop that much. With your TA so low, your pH should be fairly stable.

All acids lower TA.

 

[ant 83]

Pardon me, but I'd like to note; Dichlor is net acidic. For every 10 FC added, TA drops by 3.5. So, after 30CYA is added via dichlor, expect a 10 point drop on TA. This is enough to require a bump of buffer to prevent a PH crash when TA is at 50.

So, to make a long story short, no acid should be added until after the dichlor has, and at that point the opposite will likely be needed. In my experience 50ppm borate added via 20 mule teem isn't enough, washing soda/baking soda will be needed but only a small amount.

Acid will be needed to readjust TA increase from using bleach over time. That will take weeks of use before adjustment needed.

Make sure to retest CYA levels monthly to recalibrate FC targets. CYA loss is higher in spas than in pools due to heat and other factors. It is not predictable until you've tested a few months in a row, and have settled into a routine.

 

[JoyfulNoise]

Pardon me, but I'd like to note; Dichlor is net acidic. For every 10 FC added, TA drops by 3.5. So, after 30CYA is added via dichlor, expect a 10 point drop on TA. This is enough to require a bump of buffer to prevent a PH crash when TA is at 50.

So, to make a long story short, no acid should be added until after the dichlor has, and at that point the opposite will likely be needed. In my experience 50ppm borate added via 20 mule teem isn't enough, washing soda/baking soda will be needed but only a small amount.

Acid will be needed to readjust TA increase from using bleach over time. That will take weeks of use before adjustment needed.

Make sure to retest CYA levels monthly to recalibrate FC targets. CYA loss is higher in spas than in pools due to heat and other factors. It is not predictable until you've tested a few months in a row, and have settled into a routine.

While it is true that dichlor is net acidic and will lower pH, it’s affect on TA is a bit more complicated. Dichlor adds cyanurates (CYA) to the water and cyanurates add to the alkalinity.

At 30ppm CYA and a pH of 7.3, the TA will increase by about 8ppm from the addition of cyanurates. So the total decrease in TA from the addition of dichlor will be less than anticipated.