Help with Hot Tub Chemistry

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Chad628

Chad628

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Jul 30, 2013
101
San Francisco Bay Area
Split by moderator from HERE. Please start a new thread for your specific questions. Thanks, jblizzle

Hello. I am new to this forum and am very impressed with the collective knowledge of all the contributors. I have been doing a lot of reading on this site and have been learning about all the mistakes I have made in maintaining my pool and spa. I have a 400 gallon Artesian Island spa and had the following water chemistry readings this morning.

FC 1.5
CC .5 (most likely less as I used a 10 ml water sample for the Taylor FAS-DPD test)
TA 70
PH 7.8
CH 130
CYA 60
Borates 50 (this is an assumed number as I have some borate test strips on order and have not received them yet. I added 20 Mule Team Borax to the water in quantities based on the pool calculator this weekend).

My hot tub came with a Nature 2 mineral sanitizer which currently lives inside one of my 2 spa filters. I had also been sanitizing with dichlor and recently switched to 8.25% chlorox bleach after reading a thread about dichlor and CYA levels. I have decided to maintain the recommended FC levels based on the Chlorine/CYA chart (5 - 7 ppm based on my current CYA readings) and not trust the Nature 2 mineral sanitizer with lower levels of chlorine to sanitize my hot tub. Last night i added enough bleach to raise my FC levels to 5 ppm. based on the pool calculator.

My questions are as follows:

1. Am I on the right track with my chemistry?
2. Should I be concerned that my CYA level of 60 is much higher than the recommended 20 - 30 levels? Is this reason enough to drain my spa and start over or am I fine with just using bleach to keep my FC levels at 5 - 7 ppm? I plan on draining the spa every 4 months which would put the next scheduled draining in late November.
3. Should I ditch the Nature 2 mineral sanitizer? I have 3 more of the cartridges and planned on putting a new one in every time I drain the spa. Is there any downside to using them and maintaining Chlorine/CYA chart recommended FC levels?
4. Why would my FC levels go from 5 to 1.5 overnight when I have a CC level of less than .5? There were no bathers in the spa last night. This seems very mysterious to me.

Thank you for your help.
 
How often do you use your tub?

Have you read?: http://www.troublefreepool.com/how-do-i-use-chlorine-in-my-spa-or-pool-t10095.html

Chad628 said:
Should I ditch the Nature 2 mineral sanitizer? I have 3 more of the cartridges and planned on putting a new one in every time I drain the spa. Is there any downside to using them and maintaining FC/CYA chartl recommended FC levels?
Click to expand...
Chem geek summarized it well here: http://www.troublefreepool.com/swg-vs-nature2-question-t9168.html#p73922

Chad628 said:
Why would my FC levels go from 5 to 1.5 overnight when I have a CC level of less than .5? There were no bathers in the spa last night. This seems very mysterious to me.
Click to expand...
How "old" is your water? Typically when the 24 hour FC drop approaches 50% it is time to change the water out in a tub. Your high FC drop could also indicate a need to decontaminate the tub...there is a link to that process in the link above.
 
:wave: Welcome to TFP!!!

1. Looks like you are on the right track ... at least you have one of the good test kits ;)
2. Does not really matter as long as you maintain the correct FC level for your CYA.
3. YES. They are adding metal to your water and are just not needed if you are maintaining adequate FC. If the metal gets too high, staining and green hair can result. Now since you drain, maybe that is not going to happen, but why the added expense? Try to sell them on craigslist or something.
4. Well there must be something in the water that is consuming the FC ... there is no other explaination. Sounds like time for the SLAM process.

*** Although linen's advice may be better. :D
 
I last drained my spa in early July. The spa is new and I started using it in February this year. I use the spa 2 to 3 times a week. Mostly it is my wife and myself. We might have friends over once a month and have 4 or 5 in the spa in those situations. Due to my learning curve the FC levels have gotten to zero on several occasions in the 7 months I have been using my spa. I have slammed it a few times using dichlor. Is it possible I could have a contamination issue even if there has always been a Nature 2 mineral cartridge in the spa?

Thank you so much for your replies and excellent information. I have always had a pool service since the year 2000 and decided to do my own maintenance this year after I remodeled my pool and bought a new spa. I wish I would have found this web site sooner. I am so impressed with how well organized it is and the quality of content and knowledge of the contributors.
 
Chad628 said:
1. Am I on the right track with my chemistry?
2. Should I be concerned that my CYA level of 60 is much higher than the recommended 20 - 30 levels? Is this reason enough to drain my spa and start over or am I fine with just using bleach to keep my FC levels at 5 - 7 ppm? I plan on draining the spa every 4 months which would put the next scheduled draining in late November.
3. Should I ditch the Nature 2 mineral sanitizer? I have 3 more of the cartridges and planned on putting a new one in every time I drain the spa. Is there any downside to using them and maintaining Chlorine/CYA chart recommended FC levels?
4. Why would my FC levels go from 5 to 1.5 overnight when I have a CC level of less than .5? There were no bathers in the spa last night. This seems very mysterious to me.
Click to expand...
With a spa, it's not so much about maintaining a constant FC level as dosing with enough chlorine after your soak to handle the bather load since chlorine usage in a spa is almost all about bather load since it is so high (since the water volume is relatively low). Then you want the FC to not get too low in between soaks, but in a covered spa at hot temps algae growth is less likely. Some people prefer to start their soak with 1-2 ppm FC to minimize noticing the chlorine (it's more noticeable in a spa than in a pool due to higher volatility from the higher temps and aeration). However, with your higher CYA level it would be better not to let the FC get quite that low, probably not lower than 3-4 ppm FC would be safer.

You don't need the Nature2 with chlorine. It would become useful if you decided to use a low-chlorine approach where you use non-chlorine shock (MPS) and only use chorine once a week or so to keep the water clear. That's a more expensive approach.

As for your chlorine loss rate, you might have gotten behind in dosing. Also, if you have an ozonator, then that will increase chlorine demand in between soaks since ozone reacts with chlorine. Does your spa have an ozonator? If your FC got to zero for too long, you can get bacterial biofilms and those are chlorine resistant. If your chlorine demand doesn't return to normal after shocking (SLAM), then you may need to use Spa System Flush or Ahh-Some after which the water is changed.
 
Thank you for your reply Chem Geek. I have read many of your posts and am amazed with your depth of knowledge. Do you think the Nature2 sanitizer would have prevented biofilms from developing during the time my free chlorine was zero? I don't even know if I have an ozonator nor would I know how to tell. I will have to call the dealer and ask them. The spa that i bought was on floor of the dealership and filled with water for sales purposes. I bought it because they gave me a discount due to the fact that it was not new out of the box. They did drain it and store it for me for a long time as I was in the process of remodeling my backyard and creating a space for it. Perhaps it got contaminated during the time it sat on the showroom floor. Would draining and storing it dry for a long time decontaminate it?

Thank you again.
 
If they didn't blow out the lines to dry them, then biofilms could certainly have formed. You probably should have done a spa flush after you first got the spa. Also as you point out, if your chlorine got to zero for too long, especially if a day or more, then biofilms could have formed at that time. It's a much bigger problem in spas because of the high bather load (more nutrients for bacteria) and hot temperatures (they reproduce much faster). You can just elevate your chlorine level just in case it was getting behind your bather load and see if things return to normal.

Note that at a higher CYA level, the active chlorine level is lower so your bather load may not get handled within 24 hours as is usually the case at 30-40 ppm.
 
I just called the dealer where I bought my hot tub and found out it does in fact have an ozonator. I noticed this morning that my overnight chlorine drop was much less than I previously experienced. I think you are right chem geek in that the combination of being behind in my dosing and the ozonator are the culprits for the large overnight chlorine drop a couple of nights ago. I will continue to monitor my chlorine drop. The dealer told me they maintain their spas on the showroom floor very well and that it is unlikely that they sold me a spa with a biofilm contamination issue. I was hoping that was not the problem.
 
Chem Geek I have a follow up question for you regarding Chlorine levels in the spa and the CYA/Chlorine Chart. When I shock my spa should I still follow the recommended chlorine levels for shocking according to the CYA/Chlorine chart or is there some other calculation more appropriate for spas?

Thanks
 
For shocking the spa, you can follow the chlorine/CYA chart, but you normally shouldn't need to shock your spa at all if you dose properly after each soak. If you didn't have an ozonator, then every person-hour of soaking in a hot (104ºF) spa typically requires 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach (3-1/2 fluid ounces of 8.25% bleach) or 7 teaspoons of non-chlorine shock (MPS) to oxidize the bather waste. With an ozonator, the required dosing may be roughly half these amounts. The downside to the ozonator is that in between soaks it increases chlorine demand from roughly a 25% FC loss per day to a 50% FC loss per day. These are all estimates and depend on how clean you are when you get into the spa and on the strength of the ozonator.
 

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Wow now I am really confused. The more I read the information here the more I realize how complicated all the hot tub variables are and the pros and cons of all the different sanitation methods available for spa owners. Now that I have discovered my spa has an ozonator that has really thrown a monkey wrench in my thinking process. I had just arrived at the point where I read and learned all about the BBB method and was completely convinced this was the way to go with my spa. I was a true believer. I should have done my homework and found this website before I bought my hot tub. I would have bought a hot tub that did not have a ozonator since I only use it 2 or 3 times a week. It seems like the more practical sanitation choices for hot tubs equipped with ozonators are Nature2 with MPS and weekly chlorine shocks or Bromine.
 
Yes, that's MPS, though not as concentrated as some others -- the highest is generally 43%.

You don't sound confused, but that you are understanding the situation better. As for the ozonator, that does make chlorine spa use more difficult unless you use the spa every day or two. It means that you would need to add chlorine to the spa in between your soaks and that the chlorine loss rate is more like 50% (or even higher) than 25% (or lower if you let the water temps drop).

Some people use bromine in the spa because in that case the ozonator makes more bromine from a bromide bank in between soaks. That would be an option for you though some people don't like the smell of bromine. Also with bromine you usually need to still shock with chlorine every week or so to keep the water clear, though with an ozonator that might not be needed as often. You can read Using Bromine in a Spa for more info on bromine if you decide to try that route. You would probably just create a bromide bank and let the ozonator create bromine (after you get things started, say by adding chlorine bleach to create some initial bromine) so would not have any need for bromine tabs. You would need to add more sodium bromide when you notice that the ozonator is not able to produce enough bromine -- some bromine gets converted to bromate by the ozonator and some outgasses which is why you'll need to replenish the bromide.

Another option would be to use chlorine but disconnect the ozonator, though I don't know how to do that so someone else can help you figure that out. You'd still need to add chlorine, but it will last longer in between soaks so if you don't go more than a few days in between soaks then you could just add chlorine after each soak. At a 25% loss rate, it would go from 4.0 to 3.0 to 2.2 to 1.7 whereas with a 50% loss rate (i.e. with an ozonator) it would go from 4 to 2 to 1 to 0.5.
 
Thank you Chem Geek I think I do understand things a bit better. Since I have two more unused Nature2 cartridges and an almost full container of MPS I will try the Nature2/ MPS method over the course of my next 2 water changes. After that I will experiment with using bromine to see if that works out better for me. I am still experiencing large overnight chlorine drops in my spa. Today I am shocking the spa with 8.25% bleach with a target of 24 ppm of FC. I will check the FC 24 hours later to see where I am at. This morning I had the following readings using my Taylor Test Kit.

PH 7.5
CC .4
FC .6
TA 60
CH 130
CYA 60
Borates 80 (Lamotte Test Strips. Still scratching my head as to why i overshot my target of 50 ppm even when I used the pool calculator)

I may have a biofilm issue and may need to decontaminate. I hoped it would not come to that because I had just perfectly balanced my water including the addition of borates. I hate to throw all my hard work down the drain.
 
Just an observation here but it seems like any manufacturer of a spa with an ozonator should include some kind of on/off switch or bypass switch for the ozonator giving the owner the greatest flexibility in choosing sanitation methods. In that case someone using the BBB approach who uses the hot tub less often can just turn on the ozonator when they are soaking and leave it off the rest of the time.
 
I agree completely, but unfortunately these manufacturers don't know diddly about spa water chemistry and are focused on the lowest cost possible so don't make an ozonator an option or have an on/off switch even though ozone's reaction with chlorine is well known and documented (see this PDF file).
 
Chem Geek your point of spa industry ignorance was illustrated to me just today. I called the spa dealer this morning to ask them if there was a way to switch off the ozonator. He asked me why I would want to do a thing like that. I went on to explain the issue of chlorine being used up by oxidation in between soaks. He said to me of course I had no chlorine because it gasses off at any temperature above 96 degrees and that the ozonator had nothing to do with it. When i told him i wanted to sanitize with dichlor and then switch to liquid bleach he was horrified that I would ever put liquid bleach in my spa water and that in all his years of being in the spa business he had never heard of such a thing. He treated me as if I was out of my mind and asked why would I want bleach on my skin? I just left his comment alone and thought what does this guy think the millions of people who swim in chlorinated swimming pools are doing? I told him about CYA build up and he said he had never heard of that either and that next to the nature2 sanitizer dichlor was the number two selling item in their store. He insisted that was absolutely all I needed to sanitize after a soak.

Also today I went to a local pool supply store (not the spa dealer) to buy MPS test strips. I got into a conversation with one of their pool maintenance guys and he had no clue about the relationship between chlorine levels and CYA saying he had never heard of such a thing. I asked him what level of chlorine does he maintain his pools at and he answered 2.5 at the most. He also said I should not want any CYA in my spa and that they sold a granular chlorine (GLB SuperSonic) that had no CYA that he suggested for spas.
 
The hotter temperature does cause chlorine to react faster and outgas faster, but not by that much. Chlorine breaks down CYA which at hot spa temperatures is around 5 ppm CYA per month which translates into around 0.4 ppm FC per day at usual FC/CYA levels so that accounts for around 40% or so of the chlorine loss. The rest is from a combination of outgassing and other chlorine reactions -- all of this assuming there is no bather waste to oxidize. Even a warm pool has these sorts of chlorine losses -- my own pool loses around 0.6 or 0.7 ppm FC if not used and the opaque cover kept on but the water temp at 88ºF. There is around 0.2 ppm FC lost from oxidation of CYA and the rest from oxidation of the pool cover and other items. So your point about the spa being only somewhat more aggressive in chlorine loss than a pool is correct.

Besides, his explanation doesn't have anything to do with the fact that hot spas without ozonators lose around 25% of the FC per day while those that have ozonators lose around 50% of the FC per day and that if the pump cycle is on longer so that the ozonator is on longer then the FC loss is even greater. We've even had people with ozonators in their spas disconnect them and see the decrease in chlorine demand, then reconnect them and see the increase in chlorine demand. As you point out, spa industry ignorance is definitely palpable.

As a general rule, you don't want to tell spa or pool store people that you are using bleach. Even pool store people often think bleach is different that chlorinating liquid or pool store liquid chlorine. As for best selling items, he may be selling more Nature2, probably because he is pushing it (it's more profitable since margins on the sticks and on MPS are usually higher than on chlorine), but overall in the U.S. the number one disinfectant is chlorine (roughly 50%) which is almost all Dichlor, number two is bromine (mostly tabs with a sodium bromide bank roughly 25%) and the rest is a combination of alternatives including Nature2/MPS. Though Dichlor is popular, there are some people that run into trouble, but the CYA buildup issue would only show up for those who don't change the water frequently compared to their bather load. With Dichlor-then-bleach, people can usually go twice as long between water changes compared to Dichlor-only and when they do change the water it's not in as bad shape (i.e. not as dull).

The GLB SuperSonic is 73% Cal-Hypo so will build up CH over time and that can lead to scaling, especially in the gas heater where it is hotter. Also, if you don't start off with any CYA in the water (or build it up using Dichlor), then the chlorine will be far too strong so will oxidize swimsuits, skin and hair faster, will outgas faster so smell more and oxidize hot tub covers faster.

I'm glad we are educating consumers directly since this has generally been far easier than trying to educate the pool/spa industry, be it the manufacturers, distributors, or pool/spa store owners and personnel. It's not so much intentional deceit when it comes to pool/spa stores, but they have been told lies or half-truths for so long and are so ingrained in their current approaches that many simply cannot budge from their beliefs. Since the problems are statistical, they can always point to many happy pool and spa owners without knowing what makes the situations different nor knowing that things could be better for many.
 
I just completed my 24 hour chlorine consumption test. The results are as follows:

Beginning FC 19.5
Ending FC 8.5
Ending CC <0.5

The chlorine consumption was 56% which seems about right according to what I should expect given that I have an ozonator. I did a little research and found out that my hot tub is equipped with a Balboa Ozone Generator, CD Chip (54449).

According to the manufacturer specs the rate of Ozone production is:

Ozone (mg/hr@2lpm) 50
Ozone (ppm) 250

The ozonator is connected to my spa's circulation pump which automatically runs 24/7. I am not mathematically inclined to know what those numbers mean or if that helps explain why I consumed 56% of my chlorine overnight. Maybe there is someone in this forum that would be able to understand this.

Since my water is clean and clear and my chlorine consumption seems to make sense I am going to assume that I don't have a biofilm issue and that there is no need for me to go through the decontamination process. Would anyone concur (Chem Geek)?

Thank you so much for all the great feedback. I never intended for this thread to get this long. I think I should have started a new topic and titled it

"To ozonate or not to ozonate?.....that is the question."
 

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