Questions regarding Spa chemistry that is not found in my manuals

[Kenneth N]

I live in Sweden/Europe - so excuse me if my English might be rusty. I have found this forum giving me better information than most professional dealers in spa-products. My experience is that information is limited and dealers sometimes just guess when they advise on different topics.

I have a few questions and I not sure if I should ask them one at the time or give them separate threads. I have searched for the answers but these questions are still unsolved for me:

1. How often should I chock with MPS (if I am not using the spa/hot tub for a period of time?)

Do I still need to shock every other week/some say every week - if the spa is not used?
Taylor Technology suggested (on an e-maild question) to shock 30 minutes before bathing (if it has not been shocked for a few weeks). But what about bromine levels? If the bromine level is 4 before shocking it rises to above 15 ppm after shocking with MPS. Is that ”real” 15 ppm or is it nothing to worry about since the MPS is giving incorrect Bromine levels? What if the spa is not used in 3 months (theoretically)? Should I still shock according to the instruction label on the package?

2. If only using Bromine (and MPS for shock), do I still need to have the cover open for 15 minutes after bathing (as needed for Chlorine)?
The winter can be pretty cold in Sweden so I would prefer to close the cover if it is not necessary to keep it open.

3. Is it really the right instruction to try to keep the Alkalinity at 80-120 ppm in a spa?

I never use the pumps/jets while bathing but the pumps goes on and off according to a maintenance schedule 24/7. I have read that the pumps will rise the Ph if the Alkalinity is too high. My experience is that PH rise if my Alkalinity is at 50 or more. If the Alkalinity is 40 ppm the PH can stay stable over weeks. That is far from what all production leaflets is instructing. Is it me that is stupid, - or everyone else ;-) ? The manufacturers of the spa, the manufactures of the chemistry I buy, and the professional people selling the products all advise me to keep the Alkalinity at 80-120 and the Ph 7,0-7,4 (some advice 7,2-7,6). The first months I tried to follow the advice and set the goal to Ph 7,2 and Alkalinity at 100 (CH 210). It was only possible with a huge amount of chemistry in the spa. The Ph constantly got higher each day and I needed to compensate Ph- and Alka+ more or less every second day. I was unhappy but the dealer was happy since it was a never ending story of buying more and more chemistry to compensate. I have found Alka 40 to be the ideal level - but why is no professional instruction mention that Alka 100 is way too much for a Spa? For Pools many it is correct but for Spa?

4. CSI Help me understand - Is Ph 8,7 not building scale?

I really love the Trouble Free Pool Calculator! But I need to be assure I understand it correctly.
On a normal day I have 37 degree C (99F), PH 7,5, Alka 40, Cya 50 (Chlorine only used on the first day) CH 210.
This gives me a CSI at -0,48. It is low but not yet corrosive. Sometimes during the freezing winter, I would prefer to lower the temperature to 88 F (to save energy). But I can’t do that with the other levels listed above since the CSI drops to -0,63, correct?
On the other hand, I could let the Ph rise up to 8,7 without building scale. (PH 8,7 Alka 40, Cya 50, D88F CH 210) = CSI +0,51 (and therefore not building scale? Correct?.
I haven’t done that but I am struggling to keep my nose above -0,6 since my ideal Alkalinity is around 40.
Is CSI level of -0,48 also bad (but not as bad as -0,60)? Or is it still safe as long as it is not less than -0,80?


I have had my spa (Viskan Ekerö) for 18 months now. My Spa (Acrylic) is on 1715 liters (453 Gallons) and have a UV-C lamp. I use a floating Bromine dispenser that gives about 3 g/day (20gr/week) which gives me a bromine level of about 4-6 ppm in the water. Bathing about 1-2 times a week 1 hour and after bath adding 5 ml bromine granulate/person. Shocking with MPS 45 ml every second week. Clean filters on a regular basis and switch water 4 times a year and use pipe clean each time. TDS never goes over 1000 OSU before changing water. I test the water with Taylor Kit K-2106 and/or K-2006 2-3 times a week. I use tap water with very good quality in the spa. The Ch is at level 210 ppm. The water in the spa is always crisp clear.

 

[pooldv]

Welcome to TFP!

You are doing a nice job of learning about and managing your water despite the lack of info and incorrect info from the pros in the industry. Impressive.

This article should answer most of your questions on sanitation with bromine
How do I use Bromine in my spa (or pool)?

I prefer to use chlorine/bleach over bromine. This article explains that. Also, this article does a nice job of explaining how to manage your pH and TA.
How do I use Chlorine in my Spa (or pool)?

Now, for your questions
1. See bromine article
2. Ditto
3. No, our recommended TA level in a hot tub is 50 ppm, if 40 works better that is fine. As long as PH is stable and doesn't bounce around too much. More in the chlorine article above.
4. Yes, 8.7 pH will very likely cause scaling. Negative CSI, aka aggressive water or corrosive water, is primarily only a problem with plaster pools/Spas. Any CSI between -0.6 and 0 is completely fine in your tub. And lower to -0.8 or -0.9 will likely be fine also. I would not let CSI go above 0.3. So an ideal range for you would be between -0.6 and 0.3. See how TA at 40-50 and pH at 7.6-7.8 works.

More about scale here, Pool School - Calcium Scaling

 

[Kenneth N]

Thank you so much pooldv!

I read the links you posted but I did not get a grip on 1 and 2.

1 How often should I chock with MPS (if I am not using the spa/hot tub for a period of time?)

Both links recommended once a week (but did not differ if 10 people been in the spa or if no one been in the spa). Is the answer that it should be done once a week no matter how if it is used a lot - or not at all?

2. If only using Bromine (and MPS for shock), do I still need to have the cover open for 15 minutes after bathing (as needed for Chlorine)?

I couldn't find the answer.

Thank you so much for bringing my attention on nr 4. I missed the information that CSI below -0,60 is only a problem for plaster. I have Acrylic spa and now I can stop worrying about lowering the temperature if the spa is not used.

Thanks also for the TA recommendation on 50 for spa. Since I used Bromine I had not read the recommendation on Chlorine (the Bromine link did not mention this).

 

[pooldv]

I am not familiar enough with bromine and how it actually sanitizes to answer those questions. I tend to think yes to both based on how chlorine works and assuming bromine is similar. Chlorine tubs need some air exchange to off gas CCs which is oxidized waste. I don't shock my tub or my pool ever. Maintaining sufficient sanitizer levels on a daily/regular basis eliminates the need. But, Bromine needs MPS or chlorine to convert bromide/oxidized waste back to bromine/sanitizer. I don't know if there is out gassing involved in that process and therefore a need to leave the cover open.

We'll see if some bromine people can better help.

 

[Kenneth N]

Regarding the (in my opinion) misleading recommendation of too high levels av TA (80-120 ppm) in spa.

I hope I am not stepping on anyones toes here. I am just a beginner in this field and try to figure out why the recommendations does not apply with my experience.

As I wrote in my original post, the suppliers of chemicals and spas in Sweden all recommend to have a TA of 80-120 ppm. I appreciate Pooldv:s comforting post that I could stick with levels of 40 (which is when my water is balanced and does not force ph to rise).

But when I look around in US recommendations they are simliar to the ones in Sweden.
Taylor Technologies refer to APSP (The Association of Pool & Spa Professionals) and NSPF (National Swimming Pool Foundation). The names indicate that they should know what they are talking about but (if not Taylor in their guide book has compleatly misunderstood their recommendations - or I misunderstood). APSP and NSPF both recommend 80-100 ppm and state that one should never go below a minimum of 60 ppm.

The pool calculator in TFPS state different options between 60-120 ppm. As I understand the recommendation for my case is 60-80. So all official recommendations recommends me to try to keep the TA at around slightly below 100 (and never ever go below 60).

Well, at my age it feels nice to be a rebel breaking conventions ;-)

My theses is that the recommendation for SPA should be:
If CSI are in line with recommendations, right TA is when PH does no longer rise or decline over time. Don't try to follow the recommendation of 80-120 ppm, it is more likely the right levels are around 40-50 ppm.
Disclamer: I am a beginner in this field

 

[pooldv]

The pool industry in the US, and apparently globally, uses old, overly conservative "industry standards" that have not been updated for decades despite the science showing that those standards need to be updated. We stopped using leaches as a medical intervention a long time ago because science proved they weren't effective. They also try to have a one size fits all standard and we all know that just isn't possible, even pools right next door to each other sometimes behave differently. It is even worse that they then try to use the same industry standards for a pool in spa applications. Of course, it is obvious that spas are nothing like pools once you get past the people in water part of it.

Your recommendation is excellent. Much better informed than the industry standard. And, as you have observed, works much better in practice than their recommendation. Nice work!

 

[Kenneth N]

How far down can I go on CSI on Acrylic spa?
Poolcalculator only say minimim -0,6 on if Plaster (but I don't have plaster).
I want to lower the temperature for a period of time while not using the spa but aren't sure if that is such a good idea since I am getting closer to -1 in CSI. Or is that noting to worry about in an Acrylic spa? If no danger, how far down can I go?

pH 7,4
TA 40
CH 200
CYA 60
Borate 50
Temperature: 68 F (if not using the spa for a while)
Gives a CSI on -1.01 (is that to low?)

 

[pooldv]

There is no low limit for CSI in your tub. The caution at -0.6 is only applicable to plaster or mortar or grout in a pool. The aggressive water will dissolve calcium out of cement based products.

Are you actively lowering your pH to 7.4? If so, there is no need to do that. Let your pH hang out up to 7.8 and don't lower it until it gets to 8.0. When it hits 8.0 lower it to 7.6. This will reduce the amount of TA drop in the tub. TA at 40 can result in erratic pH. If your pH fluctuates with TA at 40 then raise it to 50 with baking soda.