City Water Report 9.2ph balancing act

[Zehribo]

Good Morning everyone!
First time user long time reader here, I recently took delivery of a Dimension One Meridian ~375 gallon ozone equipped hot tub without topside aeration controls.
Previous to this hot tub I had a ~300 gallon ozone equipped plug-and-play Roto molded unit that featured Venturi style top side aeration controls and rarely had issues with initial water chemistry. I mention the previous tub as I am having a problem ping-ponging pH and TA as many here experience, I have read pinned posts by the Chemists but my particular problem is as follows (please forgive me if the answer to my problem is in another pinned post).
After consulting my local water report from 2021 my hose end numbers from city water are:

pH:9.20 ± 0.10
Hardness:40 -60 mg/L as CaCO3
Alkalinity:40 -70 mg/L as CaCO3
2021 Water Report

Upon delivery of my new unit I brought the tub up to 102 degrees, brought TA to manufacturer recommended range 100-120 (Waterbear states lower TA in some settings is allowed) and then started on pH however I have used 10+OZ of pH down (sodium bisulfate 93.2%) over the past 36hrs with little pH relief. My Taylor K-1003 kit (the k-2006 kit is on my wedding registry currently) reads up to 8.2+ and i have yet to get reliable consistent readings much below 8.0pH. When following the Acid Demand test and the correlated sodium bisulfate 93.2% recommendations per 100 gallons factored to my ~375gal, the amount added truly is a drop in the bucket with no discernible pH change but TA drops steadily on chemical application. I added notes of air control as I have read numerous posts on this forum from informative members speaking on the byproduct of bubbles in your water and the effect that needs to be taken into consideration, and I have yet to find a way of controlling the addition of air to the water when the jets are running. The overwhelming theme on the pinned posts is that if your pH is high your TA also has to be high as they are related in nature, so my current numbers are as follows:

pH: 8.2+ (had 7.8 lastnight)
TA: 40 - 50ppm
FC: 1 - 3ppm
Temp: 102
Gal: ~375
Ozone Equipped
Filter cycle: 1hr x 4 / 24hrs (I use jets on low speed when adding chemicals, lid closed with chemical addition as outdoor temps are have been -25+)
Sanitizer: sodium dichloro-s-triazinetrione dihydrate 99%
Shock/Oxidizer: MPS 31%

Thank you to those that have made it this far! Does anyone have experience, recommendations or otherwise on how to remedy a consistent pH reading of 8.0+ when the use of pH decreasing products seemingly only effects TA. Is there something that I am overlooking or over thinking? Should I use Sodium Hydrogen Carbonate 100% to bring TA closer into range and then use Sodium Bisulfate 93.2% to drive pH down? Is there a reverse off gassing method? I am currently on the water chemistry merry go round and it sure is something! Thank you again in advance for your help, high pH + low TA is something new to me.

 

[ajw22]

pH: 8.2+ (had 7.8 lastnight)
TA: 40 - 50ppm

Those numbers are just fine. A high end pH is not going to hurt anything. You see that with your tap water report that you bathe in.

Your ozone is not helping keep your pH down.

Keep your TA at 40-50 and accept whatever pH you get.

What water test kit are you using?

 

[Zehribo]

Hi ajw22 thank you for the quick response and insight, I use the Taylor K-1003 kit as I have the K-2006 test kit on my wedding registry. From your experience pH of ~8.0 with TA 40-50ppm shouldn't case too many issues? I agree that if we shower/bathe in the city water anyways it shouldn't hurt anything, but the chemical manufacturers and the spa manufacturers sure do a good job of drilling home the point of equipment failure and scaling etc from not maintaining their prescribed water balance (although I have yet to see even rough parameters/timeline from either manufacture for either equipment failure or scaling).

 

[ajw22]

the chemical manufacturers and the spa manufacturers sure do a good job of drilling home the point of equipment failure and scaling etc from not maintaining their prescribed water balance (although I have yet to see even rough parameters/timeline from either manufacture for either equipment failure or scaling).

Think about it - do you get equipment failures and scaling from your house water?

The manufacturers have to say something simple and they give generic middle of the road recommendations. You don't have average water. You have to deal with what you have.

 

[Zehribo]

do you get equipment failures and scaling from your house water?

Not generally, although I don't have another vessel that holds water for 3 or 4 months at any given time however i absolutely understand the principal at hand and greatly appreciate your time and wisdom in the matter, doubly so because the experience from members on the forum like yourself are of actual help over generic and generalized approaches to water chemistry which have their place under lab conditions but as in my case I am ever so far from such conditions.

 

[Mdragger88]

Get a kit ASAP. Test Kits Compared
You need to be able to test for cya (so you can follow the FC/CYA Levelsat all times ). Also to be able to test ch & fc/cc with an fas dpd test. A $90 kit is a drop in the bucket compared to the cost of your new tub & will help you prevent the things you are concerned about happening.

TF-100 Test Kit

tftestkits.net

Also get some Ahhsome & purge that thing -

Ahh-Some Hot Tub/Jetted Bath Plumbing & Jet Cleaner (2 oz)

tftestkits.net

Even new tubs can contain biofilms as they are wet tested at the factory then they sit while in transit to you growing nasties so it is recommended that they be purged.
You should follow this guide

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

Be sure to keep track of how much dichlor you have added & switch to liquid chlorine when you have reached around 30ppm cya.
PoolMath effects of adding will show you how much cya you are adding with each dose of dichlor.

 

[Mdragger88]

One other thought I have about your ph rise is your water level. In my spa if I let the water level fall too low the jets create quite a bit of turbulence on the water even when they aren’t really on/are turned all the way down. This causes my ph to rise faster. In a smaller spa you often have to keep a closer eye on the water level because alot of water is lost due to bathing suits/swimming trunks.
Some people also find the need to modify their pump/filter cycle intervals from what is set at the factory so they don’t run as much when the spa isn’t being used. I have never had ozone so not sure how/if you can reduce the settings for that in your particular tub to help the situation also.
What did you use to increase your ta initially?

 

[Zehribo]

One other thought I have about your ph rise is your water level. In my spa if I let the water level fall too low the jets create quite a bit of turbulence on the water even when they aren’t really on/are turned all the way down. This causes my ph to rise faster. In a smaller spa you often have to keep a closer eye on the water level because alot of water is lost due to bathing suits/swimming trunks.
Some people also find the need to modify their pump/filter cycle intervals from what is set at the factory so they don’t run as much when the spa isn’t being used. I have never had ozone so not sure how/if you can reduce the settings for that in your particular tub to help the situation also.
What did you use to increase your ta initially?

Wow thank you for the quick responses! Initially I used Spa Guard branded Sodium Hydrogen Carbonate 100% to ~130ppm to try and allow myself a workable window as I dropped pH and also TA, but TA was the only part of the equation that measurable dropped. Currently I have the water level at the top of the escutcheon trim around the top most jets but adding another half inch or so could make a big difference in the greater scheme of things. I think you could also be right in modifying the set filter schedule, factory setting was 1hr x 2 / 24hrs but I bumped it up to 1hr x 4 /24hrs for "better performance" but that could easily be diminishing returns at the cost of rising PH. I am currently on the hunt for a model specific owners manual that speaks to the operating parameters of the factory installed ozone system! I will give those pinned threads another go round!

 

[Methuselah]

Ozone systems are controversial, but if you research as I have the bottom line is they eat up some free chlorine but have some potential to help sanitize.

Most folks here recommend muriatic acid instead of dry acid. In part because it doesn't add sulphates to your water (algae food...).

Next time you don't want to bump up alk, 40-50 range tends to help fight ph rise you get from aeration. And, @Mdragger88's advice concerning cya is the gold standard - the last thing you need is to have bad stuff flourishing in your water and plumbing!

I really liked the unique perspective about ozone provided by @RDspaguy in this post.

 

[ajw22]

Most folks here recommend muriatic acid instead of dry acid. In part because it doesn't add sulphates to your water (algae food...).

Sulfates are not algae food. I think you have it confused with phosphates.

From Acid - Further Reading

Dry acid can be used in hot tubs since it’s far easier to measure and dose small quantities of a granular substance and the water in a hot tub gets changed frequently. But, in a pool, it’s just not a good idea.

Phosphate Removers - Further Reading

www.troublefreepool.com

Ozone Systems - Further Reading

www.troublefreepool.com

 

[Zehribo]

Ozone systems are controversial, but if you research as I have the bottom line is they eat up some free chlorine but have some potential to help sanitize.

Most folks here recommend muriatic acid instead of dry acid. In part because it doesn't add sulphates to your water (algae food...).

Next time you don't want to bump up alk, 40-50 range tends to help fight ph rise you get from aeration. And, @Mdragger88's advice concerning cya is the gold standard - the last thing you need is to have bad stuff flourishing in your water and plumbing!

I really liked the unique perspective about ozone provided by @RDspaguy in this post.

I do agree that Ozone systems can live rent free in the Agree to Disagree portion of the forum given their controversial nature, I am okay with they system eating through free chlorine for the potential oxidation benefits. It is good to know that 40-50 TA is acceptable if that is what you can get to maintain relatively balanced pH in my case closer to 8.0+ than 7.5pH. I will be sure to look into the Ozone article you linked, thank you for that!

 

[Mdragger88]

Wow thank you for the quick responses! Initially I used Spa Guard branded Sodium Hydrogen Carbonate 100% to ~130ppm to try and allow myself a workable window as I dropped pH and also TA, but TA was the only part of the equation that measurable dropped. Currently I have the water level at the top of the escutcheon trim around the top most jets but adding another half inch or so could make a big difference in the greater scheme of things. I think you could also be right in modifying the set filter schedule, factory setting was 1hr x 2 / 24hrs but I bumped it up to 1hr x 4 /24hrs for "better performance" but that could easily be diminishing returns at the cost of rising PH. I am currently on the hunt for a model specific owners manual that speaks to the operating parameters of the factory installed ozone system! I will give those pinned threads another go round!

What you used was soda ash/washing soda - it didn’t help your efforts to lower ph, only drove ph higher. Next time you need to increase ta use baking soda (sodium bicarbonate) - always use PoolMath effects of adding to see all the effects on each parameter before using a product.

 

[Zehribo]

What you used was soda ash/washing soda - it didn’t help your efforts to lower ph, only drove ph higher. Next time you need to increase ta use baking soda (sodium bicarbonate) - always use PoolMath effects of adding to see all the effects on each parameter before using a product.
View attachment 466383

Im sorry now i'm confused, I used Sodium Hydrogen Carbonate 100% to raise TA initially as you had asked in your previous question with the understanding that pH would rise along with TA, but once TA was in line then further chemical additions could focus on lowering pH more than TA. This is a helpful cut sheet so thank you for that! From what it sounds like if pH continues to rise, using sodium bicarbonate to boost TA will allow me some room to lower pH via Sodium Bisulfate but the PoolMath is a very helpful and interesting tool at our disposal!

 

[Mdragger88]

To help clear things up - if your goal is a lower ph , don’t use soda ash or borax. By using soda ash you increased your ph further. As mentioned above, initially increasing your ta wasn’t necessary anyway.
Ph & TA are married chemically, each acid addition lowers them both to some degree. Your ph after adding the soda ash was likely very high. Your acid additions were affecting it but it was so high the change was not able to be measured accurately. The fact that your ta was dropping shows that your acid additions were in fact working.
For the future,
continue to control ph with acid to keep it mid 7’s-8.0.
When ta falls to 40, very sparingly add enough baking soda to get to 60 so you can continue to control ph without ta falling too low & things going wonky. I would imagine after a couple times doing this you will find ph to remain measurable & more in line with what you are used to seeing. In my tub I keep ta @50 & my ph hangs out around 7.8. When it rises to 8.0/8.2 I use enough acid to get it back down to 7.6. This is only necessary for me about once every two weeks.
Also, keep in mind that the dichlor is acidic & will lower ph/ta if you’re not mindful of dosage along with your acid dosages. Use poolmath effects of adding to see its consequences.

 

[Zehribo]

To help clear things up - if your goal is a lower ph , don’t use soda ash or borax.

Yes absolutely.

 

[Methuselah]

Sulfates are not algae food. I think you have it confused with phosphates.

This is what I found on Google:

Does sulfate cause algae?

Environmental Impact: Sulfur is an essential plant nutrient. Aquatic organisms utilize sulfur and reduced concentrations have a detrimental effect on algal growth. The most common form of sulfur in well-oxygenated waters is sulfate. When sulfate is less than 0.5 mg/L, algal growth will not occur

I'm certainly no expert and wrong far more often than not, but muriatic acid works well for me.