Salt Water Generator in Spa with TFP method

Uavmx

Well-known member
Sep 5, 2016
90
Lancaster, CA
Hello,

I had a pool and got very comfortable with the TFP methods of maintaining it, and loved it! This place is awesome. Now I no longer have the pool, but I have a 2008 Hotsprings Jetsetter JJ Spa (225 gallons) and I have several questions in general about spas, but more specifically with using a SWG. I had an intex spa, which is when I bought the Cholormatic SWG which worked pretty well, but never took the time to really learn about SPA chemicals/treatements. So here are my questions:

  1. I'm using the poolmath app on the iphone, I don't see a hot tub setting? Are all the recommendations in the app the same for a hot tub, or do they need to be tweaked?
  2. Does anything with the ozonator that's in the tub change any setting recommendations? I understand it just helps with using less chemicals to maintain?
  3. On the SWG, it recommends 1.0-3.0 PPM FC, but in this forum and app it recommends higher, which should I use? (I'm currently at 1 ppm and trying to learn how long to run the generator to maintain the appropriate level). My bathing is typically 2 people every evening, not showered. Does this change the recommendation?
    1. Is it just a matter of testing after bathing to make sure there's some FC remaining until the SWG kicks on for it's next cycle? It also has a boost mode, should I just be hitting that after getting out?
  4. On the SWG, it recommends hardness of 200-400, I'm at 125, which seems to be in line with the TFP recommendation, is this okay with the SWG?
  5. On the SWG, it recommends "0" stabilizer, I imagine it's meaning CYA? I see the TFP recommendation is 30, but doesn't discuss SWG. If I'm only using the spa in the evening (no sun), I found it interesting CYA is recommended with TFP. Does it really need to be in there with using a SWG?
  6. Lastly I've been battling the TA and PH, this seems to be the trickiest part of the spa balance act! I was well above 8.0 PH, and TA of 130. I had some Sodium Bisulfate that was given with the spa. I added that until I accidentally overshot to below 7.0 ph and TA @30. I then added Sodium Carbonate, and overshot the other direction! So I'm back above 8.0 PH, but my TA is at 50 (which I believe is recommended). I'm sort of confused on the balancing act between the two, and how to find the sweet spot. So questions to this:
    1. If TA is good, is Sodium Bisulfate what I should be using to bring down the PH? I get the feeling it's going to bring my TA down too low again? What should I target for PH on the way down? Is there a better chemical for bringing down the ph without bringing down the TA?
    2. If/when my PH is low, but TA is good, should I be adding chemicals to bring it up, or let the aeration bring it up naturally? Is Sodium Carbonate what's best for bringing it up?
    3. Is it okay to add/retest in both directions in the same day? I read somewhere to not increase and/or decrease with chemicals in the same day. Since I over shot it up today, should I use chemicals to bring it down today after waiting some period of time?
    4. When PH increases due to aeration, does it automatically bring itself down? Or it will always be necessary to use chemicals when it climbs up above 8?
    5. I don't see a Sodium Bisulfate or Sodium Carbonate option in Pool math, what are these referred to in there? (I bought the clorox brand)
I'm sure I'll have more questions, but this will get me closer to being balanced with a SWG, thanks in advance!
 
Last edited:

jseyfert3

Silver Supporter
Bronze Supporter
TFP Guide
Oct 20, 2017
1,524
Southern WI
Pool Size
15000
Surface
Vinyl
Chlorine
Liquid Chlorine
I'm using the poolmath app on the iphone, I don't see a hot tub setting? Are all the recommendations in the app the same for a hot tub, or do they need to be tweaked?
Yes, options are the same. I use a "vinyl" pool type in PoolMath.

Does anything with the ozonator that's in the tub change any setting recommendations? I understand it just helps with using less chemicals to maintain?
No, doesn't change any recommendations.

On the SWG, it recommends 1.0-3.0 PPM FC, but in this forum and app it recommends higher, which should I use? (I'm currently at 1 ppm and trying to learn how long to run the generator to maintain the appropriate level). My bathing is typically 2 people every evening, not showered. Does this change the recommendation?
You should follow the FC/CYA chart, except I follow the Liquid Chlorine chart not the SWCG chart. Hot tubs have a very high bather waste.

Is it just a matter of testing after bathing to make sure there's some FC remaining until the SWG kicks on for it's next cycle? It also has a boost mode, should I just be hitting that after getting out?
Because hot tubs are so small and hot, a soak adds a lot of bather waste relative to the number of gallons of water vs a pool. What I do is add liquid chlorine after getting out to take care of this waste. Then my SWCG takes it from there.

You can try the boost mode after getting out. If it works, great! But depending how long you soak and how hot it is it may not be sufficient. Just test the FC and figure it out. Be sure to test not just after getting out but the next morning too, and if low the next evening. After a few soaks you'll start getting it dialed in and some of the testing can be eased back. For example, I never test after I get out, I know with our soaks it will be low so I just add the chlorine then test the next day. I'm getting to the point that with just my wife and I don't even test the next day if it's just a regular soak. Extra long soaks (usually involving alcohol), especially said soaks with friends, are entirely different and often have chlorine demand that extends above average for several days, requiring extra testing and chlorine additions.

As an aside, if it's my wife and I I'm happy getting in if the FC is in the target range. If we have guests I take it up to the SLAM level before we all get in to help the FC last longer.

On the SWG, it recommends hardness of 200-400, I'm at 125, which seems to be in line with the TFP recommendation, is this okay with the SWG?
Yes, 125 is just fine.

On the SWG, it recommends "0" stabilizer, I imagine it's meaning CYA? I see the TFP recommendation is 30, but doesn't discuss SWG. If I'm only using the spa in the evening (no sun), I found it interesting CYA is recommended with TFP. Does it really need to be in there with using a SWG?
CYA is not strictly needed, but CYA is recommended because it buffers the harshness of FC. With a CYA of 30 and a FC of 12 there is less HOCl (the active part of chlorine) than there is with 1 ppm of FC and no CYA.

Lastly I've been battling the TA and PH, this seems to be the trickiest part of the spa balance act! I was well above 8.0 PH, and TA of 130. I had some Sodium Bisulfate that was given with the spa. I added that until I accidentally overshot to below 7.0 ph and TA @30. I then added Sodium Carbonate, and overshot the other direction! So I'm back above 8.0 PH, but my TA is at 50 (which I believe is recommended). I'm sort of confused on the balancing act between the two, and how to find the sweet spot. So questions to this:
  1. If TA is good, is Sodium Bisulfate what I should be using to bring down the PH? I get the feeling it's going to bring my TA down too low again? What should I target for PH on the way down? Is there a better chemical for bringing down the ph without bringing down the TA?
This takes a bit of getting used to. I'm assuming your tap water is 130? Use the acid/aeration method in the "How to Use Chlorine in my hot tub" thread stickied in this forum. Basically when you start out with a TA of 130, run all jets with all air valves open. Run until pH is 8+. Use PoolMath to calculate acid addition to target a pH of 7. Add, repeat jets with air valves open until pH climbs to 8+. Once the TA gets to ~70 start targeting a pH of 7.2 with the acid additions. Once it takes longer to reach 8 than your normal amount of in-use jets with air you can quit this process and just check/adjust before and after use as needed.

If/when my PH is low, but TA is good, should I be adding chemicals to bring it up, or let the aeration bring it up naturally? Is Sodium Carbonate what's best for bringing it up?
Always use aeration to raise pH. Hot tubs struggle with pH rise enough, never add anything to raise pH unless you accidentally add so much acid the TA is gone or the pH is below 7 and will not rise with aeration.

Is it okay to add/retest in both directions in the same day? I read somewhere to not increase and/or decrease with chemicals in the same day. Since I over shot it up today, should I use chemicals to bring it down today after waiting some period of time?
Not sure where you read that. With pools you want to wait a while (30+ minutes) between chemical additions or between additions and testing, but with hot tubs it takes at most minutes if you are running pumps with all jet valves open. After 2-3 minutes of running all jets everything should be mixed and you can test/add other chemicals.

I have a pH meter and it's fun to watch the pH stabilize after adding acid in real time.

When PH increases due to aeration, does it automatically bring itself down? Or it will always be necessary to use chemicals when it climbs up above 8?
Nope. Once it rises it stays at the higher pH, until something acidic is added.

I don't see a Sodium Bisulfate or Sodium Carbonate option in Pool math, what are these referred to in there? (I bought the clorox brand)
Sodium Bisulfate is referred to as "Dry Acid". Sodium Carbonate is referred to as Soda Ash/Washing Soda, however it only shows up in "Effects of Adding" and not on the pH adjustment (because adjusting pH up is only ever done in very odd tap water situations or if too much acid is added.

Hope this helps! Let me know if you have any other questions!
 
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jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
3,567
Morris Cnty NJ
Actually if the ozone works in the tub your approach is totally different where it applies to FC dosing. Ozone burns up FC and cc so you will have little residual amd when testing you will likely test 0 or close to it. With ozone its easier to slam the tub like a pool, and let the ozone eat it away. If using it daily, dosing small amounts ia fine amd is more like pool dosing. If a casual weekend or once in a while user, it's easier to slam it and them dose it again if you dont use it that week. All depends on usage. Cya is good at 30ish for tub. Once balanced the only thing I worry about is PH the rest stays put
 

Uavmx

Well-known member
Sep 5, 2016
90
Lancaster, CA
Yes, options are the same. I use a "vinyl" pool type in PoolMath.


No, doesn't change any recommendations.


You should follow the FC/CYA chart, except I follow the Liquid Chlorine chart not the SWCG chart. Hot tubs have a very high bather waste.


Because hot tubs are so small and hot, a soak adds a lot of bather waste relative to the number of gallons of water vs a pool. What I do is add liquid chlorine after getting out to take care of this waste. Then my SWCG takes it from there.

You can try the boost mode after getting out. If it works, great! But depending how long you soak and how hot it is it may not be sufficient. Just test the FC and figure it out. Be sure to test not just after getting out but the next morning too, and if low the next evening. After a few soaks you'll start getting it dialed in and some of the testing can be eased back. For example, I never test after I get out, I know with our soaks it will be low so I just add the chlorine then test the next day. I'm getting to the point that with just my wife and I don't even test the next day if it's just a regular soak. Extra long soaks (usually involving alcohol), especially said soaks with friends, are entirely different and often have chlorine demand that extends above average for several days, requiring extra testing and chlorine additions.

As an aside, if it's my wife and I I'm happy getting in if the FC is in the target range. If we have guests I take it up to the SLAM level before we all get in to help the FC last longer.


Yes, 125 is just fine.


CYA is not strictly needed, but CYA is recommended because it buffers the harshness of FC. With a CYA of 30 and a FC of 12 there is less HOCl (the active part of chlorine) than there is with 1 ppm of FC and no CYA.


This takes a bit of getting used to. I'm assuming your tap water is 130? Use the acid/aeration method in the "How to Use Chlorine in my hot tub" thread stickied in this forum. Basically when you start out with a TA of 130, run all jets with all air valves open. Run until pH is 8+. Use PoolMath to calculate acid addition to target a pH of 7. Add, repeat jets with air valves open until pH climbs to 8+. Once the TA gets to ~70 start targeting a pH of 7.2 with the acid additions. Once it takes longer to reach 8 than your normal amount of in-use jets with air you can quit this process and just check/adjust before and after use as needed.


Always use aeration to raise pH. Hot tubs struggle with pH rise enough, never add anything to raise pH unless you accidentally add so much acid the TA is gone or the pH is below 7 and will not rise with aeration.


Not sure where you read that. With pools you want to wait a while (30+ minutes) between chemical additions or between additions and testing, but with hot tubs it takes at most minutes if you are running pumps with all jet valves open. After 2-3 minutes of running all jets everything should be mixed and you can test/add other chemicals.

I have a pH meter and it's fun to watch the pH stabilize after adding acid in real time.


Nope. Once it rises it stays at the higher pH, until something acidic is added.


Sodium Bisulfate is referred to as "Dry Acid". Sodium Carbonate is referred to as Soda Ash/Washing Soda, however it only shows up in "Effects of Adding" and not on the pH adjustment (because adjusting pH up is only ever done in very odd tap water situations or if too much acid is added.

Hope this helps! Let me know if you have any other questions!
Thank you so much! Very very helpful! Running the pumps did bring up the ph to a perfect spot, so I think I'll have an easier time managing it now. Boost mode does seem to keep the water clear, I have actually turned it down from a setting of 5 to 4. I am getting a chlorine smell when opening the top, but testing still tends to show .5-1 FC, and .5-1 CC. What's the best way to get the CYA up for a salt tub? Still confused with the FC/CC levels due to the ozonator, which is what jimmythegreek is saying:
Actually if the ozone works in the tub your approach is totally different where it applies to FC dosing. Ozone burns up FC and cc so you will have little residual amd when testing you will likely test 0 or close to it. With ozone its easier to slam the tub like a pool, and let the ozone eat it away. If using it daily, dosing small amounts ia fine amd is more like pool dosing. If a casual weekend or once in a while user, it's easier to slam it and them dose it again if you dont use it that week. All depends on usage. Cya is good at 30ish for tub. Once balanced the only thing I worry about is PH the rest stays put
This is what I'm experiencing....low reading despite running the unit at setting 5, now 4, which is above what's recommended for my gallons. So what am I supposed to do, how do I know if I'm on the right setting of the SWG? Is it just a matter of having the water clear based on our bathing habits? Shock it if/when it gets cloudy on a heavy usage (partying with friends)? Not sure what do to in this area, but looking forwards to only having to be concerned about ph!
 

jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
3,567
Morris Cnty NJ
With ozone I dont really think a SWG is needed. I use tub 1 to 2x a week. I run no floater. I splash the tub heavily after long use and a small splash every 5 to 7 days of non use. No measuring, just by eye. I do the quick ph test once a week and check FC here and there. In your case I would just turn it down and splash the spa with a little liquid after using it, heavier with heavier use
 

Uavmx

Well-known member
Sep 5, 2016
90
Lancaster, CA
With ozone I dont really think a SWG is needed. I use tub 1 to 2x a week. I run no floater. I splash the tub heavily after long use and a small splash every 5 to 7 days of non use. No measuring, just by eye. I do the quick ph test once a week and check FC here and there. In your case I would just turn it down and splash the spa with a little liquid after using it, heavier with heavier use
My wife and I use it pretty much every evening, we like the feel of the salt and just want no mx. I had 4 people in the other night and the next morning it looked perfect! So I turned it down another level. But again, how do I test? Or do I just go off clarity?
 

jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
3,567
Morris Cnty NJ
Just splash a little liquid when using it heavy, otherwise keep adjusting the swg settings. The key for testing in the beginning is watching your FC and CC. As long as CC stays low or non existant then your good. Every tub is like a pool. You learn what it wants amd how it reacts to your actions amd becomes a routine sort of speak.
Does your tub have a 24/7 circulator pump or does it run on cycles off low speed pump