- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
You should by muriatic acid next time. Sodium bisulphate adds sulphates to your water which can cause scale & corrosion
Hello from Florida. New Hot Tub Owner
- Thread starter WaldenTW5
- Start date
Sodium Bisulfate is "dry acid". I would be leery of using it in liquid format, unless you know the strength that you are using. Dry acid is 93% sodium bisulfate.
The problem with Sodium Bisulfate is that the sulfates build up pretty quickly in the water, and once you hit about 300 ppm of sulfates, you can cause damage to metal parts (your heat exchanger)
The good news is that not only is MA better, it is cheaper too. You do have to be careful with it. As in taking care, not scared of it.
Thanks!! Just added 2 oz of muriatic acid a few hours ago. TA is at 130ppm now. It was 140 before adding. pH is still at least 8. I have read conflicting advice on whether or not to have the jets running when trying to lower TA and pH. Yea or Nay?
- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
1st off, You want the acid to get mixed well so 5 minutes is good enough for that.
Adding acid lowers ph & ta.
Aeration (running the jets) for an extended time increases ph without raising ta thus allowing you to lower them both again with acid. You can repeat this cycle as many times as you wish to achieve the ta you desire.
Thanks! Just tested this morning and logged in PoolMath. FC 3.2, TA 110, pH 7.4, and CH 190. I just added about 2.5 oz of MA to lower the TA and I’ll test that and the pH again and may need to run the jets at full speed with all the air opened up to raise that pH. One shocker, as I was looking at the PoolMath info, it showed CH Recommended range: 250-650 and Ideal range: 350-550 with a target of 450! That is way off from everything I’ve read about CH. I’ve seen that CH for a hot tub should be between 175ppm and 250ppm. Mine is at 190 right now. Is there something I’m missing here? Thanks so much for your help. I am going to go in and make a donation because the information I’ve received here has been invaluable!
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- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
It is because you selected fiberglass, if you change it to vinyl it won’t say that.
Also when lowering ta you never want the ph to drop below 7.
Allow ph to rise to 8 (naturally or via aeration) then lower to 7.2, repeat if necessary.
Ahhh! I believe it is acrylic…but I’ll change it to vinyl. Thanks! Gotcha about the pH. I currently have everything opened up and aerating. The TA was 90 after the last dose and the pH was 7. Thanks again!!
They all look like $. I'm just wondering if there is a visible difference between the results. Heaters have a variety of looks when they go bad, but I can only account for some. I recognize dry-fire/boil-out, scale insulation, tube contact, and corrosion, but I have no idea the difference between ph corrosion, oxidation, and now sulfates. But I know not all heaters corrode the same. Some get rusty streaks or spots, while others get big bubbly corrosion, like car battery terminals, of varying color. Never can tell, maybe @phonedave knows, or someone else here. Lots of knowledge among the members of this forum on a variety of subjects. I've been surprised on numerous occassions at the info that pops out randomly in some of these threads.@JamesW and @JoyfulNoise come to mind on effects of chemistry vs. heater failure pathology (did I choose the right word). Might be more of a "deep end" discussion?
I was thinking an answer is all that's needed. Put me in the deep end I might never find my way out!
That is outside my area unfortunately. I do know they attack metal in heat exchangers. I believe it is scaling, in the form of Calcium Sulfate, as opposed to pitting or erosion.
It is also not good for concrete or rebar either
Ok, so I think I’m getting this mostly down pretty well. I’ve been using the Pool Math app to log tests and chemicals and things are pretty clear to me. One question I have though, is how much FC do most people like to keep in their hot tub on a daily basis? We like to go in daily…just my husband and me…sometimes just me. I’ve read repeatedly that you should not go in if the FC is above 3…but I see in the Pool Math calculator that it is recommending that with my CYA level of 45, I should be targeting 4-8 FC. Does that just mean the shock level? I know that in the thread from Nitro about how to use chlorine in a hot tub, he recommends what seem like pretty high levels of FC :
“We'll go with the easy one first, two people, showered, no suits etc. (Note: Some people prefer to use the tub with very little FC. That's your choice. I'm just telling you how to determine how much FC you're using in a safe manner). Test your FC and add Chlorine to get to 5 ppm FC. After one hour of soaking test FC again. If you find you have no FC after an hour, next time start with 6 or 7. If you find you still have 3 ppm FC, next time it's safe to start with 3-4 ppm FC. Get it? The trick is to have the lowest amount of FC without ever dropping to zero. If you plan on staying in the tub longer than an hour, either start out with more FC, or add some during the soak. However, you don't want to get into the tub with the FC much above 8, unless of course you like a strong smell of chlorine. I got in once with FC at 10, and it was a little too much for me, and I like the smell of Chlorine.”
I’m thinking I should be shocking my hot tub about once a week. If I turn the toggle on for SLAM, it says my FC target is 8…when the toggle is off, it says my target is 6. Again, that seems really high to me.
Thanks again for all the wonderful guidance here!
“We'll go with the easy one first, two people, showered, no suits etc. (Note: Some people prefer to use the tub with very little FC. That's your choice. I'm just telling you how to determine how much FC you're using in a safe manner). Test your FC and add Chlorine to get to 5 ppm FC. After one hour of soaking test FC again. If you find you have no FC after an hour, next time start with 6 or 7. If you find you still have 3 ppm FC, next time it's safe to start with 3-4 ppm FC. Get it? The trick is to have the lowest amount of FC without ever dropping to zero. If you plan on staying in the tub longer than an hour, either start out with more FC, or add some during the soak. However, you don't want to get into the tub with the FC much above 8, unless of course you like a strong smell of chlorine. I got in once with FC at 10, and it was a little too much for me, and I like the smell of Chlorine.”
I’m thinking I should be shocking my hot tub about once a week. If I turn the toggle on for SLAM, it says my FC target is 8…when the toggle is off, it says my target is 6. Again, that seems really high to me.
Thanks again for all the wonderful guidance here!
- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
You didn’t read that here. Proper Fc level is based on cya level.
You never want the fc to fall below minimum for your cya lest nasties WILL grow.
It is safe for swimmers & equipment with fc anywhere between minimum & slam level for your cya.
FC/CYA Levels
Thanks! You’re correct, I didn’t read that here. I’ve read it in other places on the internet and on my bottle of Dichlor granules it says “Re-entry into treated spas is prohibited above levels of 3 ppm.”
- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
That is a prime example of “old” practices which do not take the fc/cya relationship into account. The industry is slowly changing but it’s got a long way to go. I bet the bottle also probably tells you to blindly add it weekly whether you need it or not & it may even say to put it in the skimmer/filter area which is a big no no.
CYA Chlorine Relationship - Further Reading
www.troublefreepool.com
No, it doesn’t give a set timing to add or shock, but it does say to not allow CYA level to exceed 150ppm…that seems really high since I know it’s recommended to maintain it between 30 and 60 according to the calculator.
- Jun 1, 2018
- 16,099
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Some pool stores go by that train of thought too sadly. Then next they tell you that you have “chlorine lock” (not a thing) & $ell you something to “fix” it.
While 60ppm of cya is doable, Any cya over 50 makes a hot tub a bit hard to maintain specifically because of the need to often raise fc higher than target fc levels to ensure minimum is never broached due to the nature of high bather loads.
At 50 or 60 cya this could often mean 10ppm or higher which then makes accurately testing & maintaining ph complicated as fc above 10ppm makes the ph test inaccurate.
The
PoolMath calculator was designed well, for pools, that’s why there’s no choice for acrylic for instance. Don’t just blindly follow it’s target suggestions. Cross check them with the suggestions in the sticky which are laid out to keep the spa sanitary & easy to maintain as it’s a different environment than a pool.
Higher concentration of fc DOESN'T cause a strong smell of chlorine. What you smell is chlorimines because you didn't have enough fc.
Too, what I find is testing right after getting out does not work - no, can't say why but only guess. I test regularly and know what my daily loss will be. When it gets used, testing right after will not reflect the demand until the next morning. Knowing that, I anticipate the demand and dose for it, and the following night CHL test is pretty much right where expected.
If you have to shock the tub, the preceding may be why ... you will have sanitation issues any time you don't have the necessary fc, and that doesn't mean just when you check it.
Higher concentration of fc DOESN'T cause a strong smell of chlorine. What you smell is chlorimines because you didn't have enough fc. (really)