If I am using bleach to re-activate the bromide in my spa, could some of the chlorine oxidize waste and form chloramines? Also, should I ensure I have some CYA in my bromine spa when shocking with chlorine? I was wondering if adding bleach without some CYA in a bromine spa might be a little harsh.
Chloramines in a Bromine Spa?
- Thread starter Tibo
- Start date
The chlorine will very quickly react with bromide in the spa to form bromine, likely nearly all of it before the chlorine reacts with organics (bather waste). You will have some chloramine production if there is bather waste present, but fairly minimal. This assumes that you have enough of a bromide bank to fully consume all the chlorine added, converting bromide to bromine. For example if you only had 20 ppm bromide bank and decided to add 30 ppm of chlorine, you'd end up with 20 ppm bromine, 10 ppm chlorine in the spa. A bromide bank of about 30 ppm is recommended so that even if you accidentally added 30 ppm chlorine, you'd have enough bromide to convert to bromine. Bromine can actually outgas a bit over time as well so your bromide bank may decay slightly between water changes, hence the 30 ppm recommendation. If you ever use a bromine tablet, that will also add some residual bromide to the spa as well.
Long story short, you do not need CYA in your bromine spa.
Long story short, you do not need CYA in your bromine spa.
Wow, fast reply! Thanks. I am trying bromine for the first time. I was using dichlor then bleach previously. I've poured through many of these threads so I feel I've got a good handle on most of it but I've got one more question for you if you don't mind. What you said makes sense to me. I put in 2 oz. of pure sodium bromide on start up which was supposed to give 30ppm bromide for 400 gal. My tub is 450. I have a floater in there as well. On start up, I put in 1.5 cups of 6% bleach and got a reading of bromine that exceeded my test kit. After 16 hours it fell to 7ppm and we hopped in. It fell to 3 ppm after our soak and I left it to see what the floater would do. 24 hours later, it was at 2ppm and some friends were coming over so I put in 1/4 cup chlorine but didn't test it. There was 5 of us in the tub for about 30 minutes. After we got out, I put in 1.5 cups of bleach, and left the lid open with the water circulating for 30 minutes. I re-tested and got a zero reading for bromine. I was surprised at that so I put in another cup of bleach and after 20 minutes, I got a reading of 4 ppm so I left it. This morning, I was at 2 ppm so I added a quarter cup of bleach and after 20 minutes I got a reading of 3ppm.
My question: When I added the 1.5 cups of bleach after the group got out, would that bleach have converted the bromide to bromine and then the bromine was completely used up oxidizing waste within the 30 minutes? If so, that is fast! When I was using chlorine, I know that adding bleach would cause a spike in chlorine readings and it would gradually be used up over several hours. I never added 1.5 cups of chlorine, retested 30 minutes later and got a reading of zero. Can you comment on what I witnessed? I am assuming that if I would have added 2.5 cups of bleach after the party, I would have tested 4ppm after the 30 minutes. Thanks for any feedback.
That level of bromine demand is not unheard of. I'm assuming 8.25% bleach. I would say it depends on many factors (such as did folks shower or rinse before going in spa, how hot was the spa, did anyone *ahem* relieve themselves in the spa?) but a general guideline is each bather will consume 7 ppm per hour in a 350 gallon spa. 5 X 7 X 0.5 = 17.5 ppm average demand. You did the right thing by adding what you assumed would cover the bather load, then retesting after 30 minutes. Make sure you can bring the sanitizer level up to 4-6 ppm bromine and get it to stick for 30 minutes before assuming the bather waste has been handled. You could add a bit more bleach than that next time on the initial post-soak treatment after a similar bather load, say 2 cups and check from there.
Thanks so much for your help. I have one more on the topic of CYA in a bromine spa. Lets say I use dichlor instead of bleach to reactivate the bromide and I get my CYA up to 200+ over a couple of months. Won't that high CYA amount inhibit the chlorine from reacting with the bromide? My understanding is that a high CYA reading in a chlorine spa makes the chlorine less effective. Why wouldn't it be the same in a bromine spa?
I don't have enough knowledge of the equilibrium between how fast FC will be bound to CYA versus FC oxidizing bromide. You have two reactions going on when you have both bromide and CYA in the spa and add hypochlorite. Simplistically:
CYA + Chlorine <=> Chloramides (Chlorine bound to CYA)
Bromide + Chlorine <=> Bromine + Chloride
There is also the possibility that Bromide may be able to "pull" bound chlorine off of CYA, but I don't know enough about these equilibria to give you a great answer. My suspicion is that the bromide would be oxidized faster than the chlorine would become bound to CYA and you would be fine using dichlor to shock your bromine spa for some time. However, once you get to higher CYA levels (>100 ppm) it may become less effective at oxidizing your bromide back to bromine. Unless you have a lot of dichlor already laying around, bleach is cheaper anyway.
CYA + Chlorine <=> Chloramides (Chlorine bound to CYA)
Bromide + Chlorine <=> Bromine + Chloride
There is also the possibility that Bromide may be able to "pull" bound chlorine off of CYA, but I don't know enough about these equilibria to give you a great answer. My suspicion is that the bromide would be oxidized faster than the chlorine would become bound to CYA and you would be fine using dichlor to shock your bromine spa for some time. However, once you get to higher CYA levels (>100 ppm) it may become less effective at oxidizing your bromide back to bromine. Unless you have a lot of dichlor already laying around, bleach is cheaper anyway.
I'm guessing his dichlor is coming from the tabs in the floater. Probably not enough coming from them to get the CYA to excessive level.
Dichlor is only sold in powder form. Trichlor comes in tablets of various sizes. Small trichlor tablets can sometimes be used in a spa, but not generally recommended here.
I have a powder product that mixes dichlor and sodium bromide that I was sold at a pool shop that I was too lazy to return. I won't buy it again, but I have it so I use it on occasion. The tabs I have are from Rendezvous. They do have chlorine in them. 1-bromo-3-chloro-5,5-dimethylhydantoin, 1,3-dichloro-5,5 dimethylhydantoin, 1,3-dichloro-5-ethyl-5 methylhydantoin. They list it as 39% available bromine and 44% available chlorine.
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