Bromine System - looking for corrections/advice

Osric

Member
Jan 29, 2018
7
Muskoka
This is derived in large part from TFP’s “How do I use Bromine in my Spa (or pool)?” and “How do I use Chlorine in my Spa (or pool)?”.

It is written custom for my own Marquis Epic spa (450 gallons = 1700 liters) for the 3-step system since this spa often goes for weeks unattended.

I’m looking for feedback on mistakes I’ve made, recommendations for changes to my plan, links to products that people prefer to use. I’d like this to come out as an easy to follow and understand reference document. Thanks.
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Sodium Bromide is used to create a bromide reserve in the water. Bromide itself doesn’t have any direct positive or negative effect on the spa, but it is turned into bromine by shocking the spa, and bromine then sanitizes the pool by oxidizing dissolved waste.

Sodium bromide seems to be a bit hard to find by that name. Try looking for the following products:

Two ounces (55g) of 100% pure sodium bromide should be good to set up the initial bromine bank for 1700 liters, and/or follow the manufacturer’s directions for the product you bought. I have not found a way to measure/ensure that the bank is at the right level, but the goal is about 30ppm and if you are adding pure or known concentration sodium bromide you can calculate it based on your spa volume (e.g. 0.000030 * 1700000 = 51g).

Sodium bromide converts into bromine each time you shock the spa, and is also activated by your ozonator if you have one. The cheapest way to shock the spa is with unscented chlorine bleach, whose active ingredient is sodium hyperchlorite. Approximately 25ml of pure sodium hyperchlorite should be good for a 500 gallon spa, or let’s say 20-23ml of pure sodium hyperchlorite for my particular 450 gallon spa. It looks like 1 cup of Chlorox (8.25%) should be sufficient to shock my spa. After shocking, bromine levels should spike to above 10ppm. Target level for bromine in my spa is 4ppm, and the spa can be used from 4-8ppm. I typically shock the spa upon arrival. If the spa is seeing extremely heavy usage (10+ bathers in a day), I do a smaller shock at the end of each day.

The Taylor K-2106 test kit is the recommended test kit. Test and correct water chemistry levels every morning that the spa might get some use (target bromine: 4ppm, pH 7.5, TA 50ppm, CH 150ppm). In my area, CH starts at close to zero so it is the first parameter to be adjusted on water changes. Then TA, and then bromine. pH normally comes out at an acceptable level without being directly adjusted (7.3-7.7). I plan to refill the tub every 4 months.
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Thanks again for help/recommendations
 

MPurcell

Well-known member
Feb 17, 2017
105
Dahlonega, Georgia
Seems like you have a pretty good grasp of the chemistry. I would make a couple of observations based on your write-up.

You say you are following the three step method, but don't mention using a floater. I would assume that you are using BCDMH tablets in a floater to keep the bromine level up during periods of no usage. First, I would emphasize the importance of never ever letting the bromine level fall to zero. If you go long periods without checking the chemistry, then you should be sure of the amount of bromine that your floater is adding daily. Ideally, it should be enough to keep the bromine at the same level from day to day. I found it somewhat difficult to get the floater to keep up with the bromine demand of the tub.

BCDMH bromine tablets are quite acidic. When you use enough tablets in the floater to keep the bromine level up over several weeks in a 450 gallon tub with no bathers, the pH may drop significantly. It is best if you can keep pH in the proper range continuously, but if you have to bring it up frequently, then you might consider using borax to prevent raising TA too much.

You mention having a heavy bather load when the tub is in use. Bromine level can go down very quickly with a high bather load, especially if the water is very hot, so I would suggest that you be sure to understand the correlation between bather load and the amount of bleach you must add to neutralize bather waste. Also, with a high bather load, you should be extra careful not to let the bromine level fall to zero while the tub is in use, especially since the floater should be removed when bathers are present.

The recommended period for changing the water is three months. You might push it to four months depending on overall number of days of usage. If the total number of days is fairly small, then you should be okay with four months, but I personally wouldn't go longer than that.

I would also recommend that you maintain about 50 ppm of borates in the water. You may have read about this, but the best way to add borates is with granular boric acid which you can obtain from Duda Diesel, Florida Laboratories, Inc, or similar company.
 

Osric

Member
Jan 29, 2018
7
Muskoka
You say you are following the three step method, but don't mention using a floater. I would assume that you are using BCDMH tablets in a floater to keep the bromine level up during periods of no usage. First, I would emphasize the importance of never ever letting the bromine level fall to zero. If you go long periods without checking the chemistry, then you should be sure of the amount of bromine that your floater is adding daily. Ideally, it should be enough to keep the bromine at the same level from day to day. I found it somewhat difficult to get the floater to keep up with the bromine demand of the tub.

Thanks for your informative reply! I haven't added the floater to the procedure yet because I don't know how much bromine will get activated by the ozone on my spa and how many tablets need to be in the floater to have the combined effect of keeping the bromine @ 4ppm. I don't know how to determine the right amounts except for experimentally: if you have suggestions that'd be great.

BCDMH bromine tablets are quite acidic. When you use enough tablets in the floater to keep the bromine level up over several weeks in a 450 gallon tub with no bathers, the pH may drop significantly. It is best if you can keep pH in the proper range continuously, but if you have to bring it up frequently, then you might consider using borax to prevent raising TA too much.

I probably have not been doing it right up to now, because my pH never drops too low. However bromine does drop too low, possibly even to 0 as you've said never to allow.

You mention having a heavy bather load when the tub is in use. Bromine level can go down very quickly with a high bather load, especially if the water is very hot, so I would suggest that you be sure to understand the correlation between bather load and the amount of bleach you must add to neutralize bather waste. Also, with a high bather load, you should be extra careful not to let the bromine level fall to zero while the tub is in use, especially since the floater should be removed when bathers are present.

Heavy load is a 1-3 time/year occurrance. Most of the time the tub has just me and my wife using it, or perhaps two couples, once or twice in a weekend. For occasions like thanksgiving, there is a crazy influx as the whole family is over and the tub could see 15 bathers in a single evening. The tub is normally @ 100F or 99F, so it isn't super hot.

The recommended period for changing the water is three months. You might push it to four months depending on overall number of days of usage. If the total number of days is fairly small, then you should be okay with four months, but I personally wouldn't go longer than that.

OK I'll have to keep this in mind. In a typical four month period, the tub might get used by 2-4 people perhaps 6 times. The summer's another story, so probably a water change just before summer begins and perhaps also late-summer would be optimal (e.g. June + end of August).

I would also recommend that you maintain about 50 ppm of borates in the water. You may have read about this, but the best way to add borates is with granular boric acid which you can obtain from Duda Diesel, Florida Laboratories, Inc, or similar company.

I haven't read about borates. I'll do some searching.

Thanks again for your helpful reply!
 
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