First Hot Tub Fill - Seeking Advice on Goals and Balance

[contentedPilgrim]

For a new 370 gallon Sundance Spa, did a new fill last night. It has ozone and UV.
My initial water balance had TA: 50 ppm and Calcium: 40 ppm.
I adjusted TA to 80 ppm and Calcium to 140 ppm. pH read 7.8 and I adjusted to 7.6.
I added 15 fl oz Boric Acid so borates were 50 ppm.
I added way too much dichlor (5 tsp) and FC was over 14.
With above settings, Saturation Index (SI) was 0.

This morning:
pH: 8 => Added dry acid
After 15 minutes:
pH: 7.4
TA: 50 ppm
FC: 8 (Lid is now open to expose to direct sunlight for a few hours)

Using the calculator, my SI is low (-0.44) with these settings (104F). If I were to adjust to TA = 80 and pH = 7.6, the SI would be balanced.

I presume with aeration and time, the pH will creep upwards. I'd appreciate advice on targets and whether I should raise TA with baking soda to 80 ppm. I expect an ongoing circle of raising TA to 80, pH creeping up, adding acid, TA dropping and being in the same place.

Thanks for any advice.

 

[JoeSelf]

I have a sundance also. I found that with a TA near 50 my PH rise is very slow.

 

[Mdragger88]

Ta around 50 - 60 is actually recommended for spas to help with the ph rise due to all the aeration.
Muriatic acid is best - dry acid adds sulphates which aren’t great for your heater.
You mention si -
Here we use csi. Which also takes cya into consideration. Which you don’t list.
Are u using PoolMath?
That much dichlor should have had this approximate effect - perhaps your volume is a bit smaller than estimated.

Follow this guide
It is also pinned to the top of this sub forum.

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.troublefreepool.com

 

[Mdragger88]

Also, did u do an Ahhsome purge to rid your plumbing of biofilms? If not you should sooner than later.
Even new spas often contain biofilms since they are wet tested at the factory & its impossible to evacuate all the water from the lines things grow while it is in transit to u .

what is ahh-some?

What is Ahh-some?

www.troublefreepool.com

 

[JoeSelf]

Here is the pic of what came out of my new spa. Wiped it continuously during the purge. Filled a plastic shopping bag half way with the rags. And i am using their AquaClarity product, along with filter cleaner, scum rays and Ahh!some.

IMG_20220629_142812_01.jpg

• JoeSelf
• Jul 1, 2022

 

[Ahhsomeguy]

Thank you for your support and confidence in our products Joe. Your next purge will be very light with biofilm since you are using our Aqua Clarity product on a weekly basis.

 

[contentedPilgrim]

Muriatic acid is best

Thanks, I'll have to order online. CERTOL Replacement Acid for $17 from Amazon is the best I can find. Any tips on a better / less expensive option?

You mention si -
Here we use csi. Which also takes cya into consideration. Which you don’t list.
Are u using PoolMath?
That much dichlor should have had this approximate effect - perhaps your volume is a bit smaller than estimated.
View attachment 441851
Follow this guide
It is also pinned to the top of this sub forum.

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.troublefreepool.com

What is the calculator's assumption for when FC is measured? It wasn't 9.3 until at least 12 hours later.
I have been using poolcalculator.com. I've got the PoolMath app now and see your numbers. Thanks. With the Taylor kit, I can't test for CYA under 30, so I'm estimating the CYA. My estimation was 9 ppm so this was close.

Also, did u do an Ahhsome purge to rid your plumbing of biofilms? If not you should sooner than later.
Even new spas often contain biofilms since they are wet tested at the factory & its impossible to evacuate all the water from the lines things grow while it is in transit to u .

I did an initial purge with "SeaKlear Spa System Flush". I had it leftover from the previous spa. I'll switch to AhhSome at some point.

Here is the pic of what came out of my new spa. Wiped it continuously during the purge. Filled a plastic shopping bag half way with the rags. And i am using their AquaClarity product, along with filter cleaner, scum rays and Ahh!some.

My spa didn't give off as much scum as yours - maybe 5-10% of that brown stuff - but a LOT of foam!

I left the cover off for a few hours. The FC went to ZERO. The tub got to 109F in the sun (hot day). Going now to add a bit more dichlor. I will take it slow, one teaspoon (2 ppm) at a time.

**UPDATE**
What should have raised the FC to 2 ppm gave me 2.4 ppm. That confirms I certainly didn't fill the spa fully (by extrapolation, only 300 gallons). So, I added more water until just below the lowest pillow. I don't remember anywhere the manual showing how far to fill it up. I figured, when 2 people get in, you don't want it raised so high that your nose is under water

 

[Mdragger88]

I buy Muriatic acid at Home Depot, lowes, ace hardware etc. in person. It’s about $17 here for 2 gallons of 31% strength.
The gist of things is:
*Always stay above min for your cya FC/CYA Levels lest nasties will grow.
The lowest fc should fall even with no cya is 2ppm to prevent person to person transmission of pathogens
Hot tubs are people soup - chlorine is your friend here.
Most who manually dose find that raising fc to slam level for their cya or near it after a soak allows for them to not fall below minimum before the next use/dose. Ymmv- especially if using the tub alot since it is new. It is safe to swim with fc levels anywhere between minimum & slam level for your cya- so long as u can see the bottom for safety reasons.
Testing fc before & after using the tub will help u see what your average use consumes as well as your standby consumption so u can compensate & dose for both ensuring u don’t fall short.
Example - 2 people/30 min = x fc.
1 person/30 min = x fc.
12 hrs of standby = x fc.
You’ll find your groove
* When calculated cya gets to 30ppm switch to liquid chlorine
- Cya will lower overtime due to splashout/water replacement & degradation from the heat so I use a little dichlor once every week or two to replenish cya
*When using dichlor be aware of it’s acidic effects as well before also reducing ph with acid. Use poolmath effects of adding beforehand so u know what will happen.

If u find the standby dosing a chore you can add a drape over swg to do the heavy lifting for u. I use a saltron mini on a timer so the fc level stays pretty steady in my tub & then I just replace what is consumed during my soaks manually. If it’s a short session i may just turn the swg on again.
ControlOmatic also has drape over swg’s- one is designed to be automatic. They cost a bit more than the saltron mini.

The ozone & uv are oxidizers - they will oxidize your fc too, not just cc’s. When u use the tub alot (daily) they are a helping hand because u have alot of bather waste for them to oxidize but for periods of no use they can kinda work against u as they are then just oxidizing your residual fc. So keep an eye on that. For that reason some people choose not to replace them when they go out.