Debating between chlorine and bromine...

I've had my swim spa (1500 gallon)for about 4 weeks now and realized about a week into it not to trust the advice I received at my spa dealer!

They were asking me to shock my pool each week with Dichlor, and now my CYA level is between 50-60. I do seem to need a lot of dichlor on a regular basis. (we swim in the spa almost daily).

Considering adding bleach when needed (and giving the pool guy at Leslie's a coronary) vs. switching to bromine tablets. Pool guy from Leslie's suggested Cal Hypo instead but my Ca level is perfect right now and I don't want to mess with it.

I read the bromine sticky and purchased some bromine tabs as well as bromide powder to create a bromide reserve. Questions:

1. Should I switch or not? I'm a little concerned since I travel and may not be able to check the pool for up to a week.

2. I notice the bromine tabs for the float have additional chlorine in them, I presume to oxidize the bromide to hypobromous acid. See below. Is the 1,3 dichlor-5,5-dimethylhydantoin that is mixed with the bromide the same as the "Dichlor" in my shock. Will it raise my CYA levels? Does it matter? Answered...

3. What level of free chlorine should I start this process? Wait until it's low? Does it matter?



Edited to add: I figured out the DMH is the stabilizer with bromine and is analogous to CYA, so I answered that question.



TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
You're going to want to be careful as you now have copper in your water. That copper can easily cause stains if your oxidizer levels get too high. I would suggest you drain some portion or all of the water and start over. You could drain half and have a decent CYA level and stick with chlorine.

Can you use salt in your spa? If so, there are salt water chlorine generators that are designed to be draped over the side and used to maintain FC.

I'm not a huge fan of bromine and once you do switch to bromine there's no going back unless you drain. Also, bromine is going to be no easier to maintain than chlorine. Even with a tablet floater your bromine levels will be all over the place.

Up to you of course. Do what you think is best for your personal situation.

Sent from my iPhone using Tapatalk
Feb 17, 2017
Daniel Island, SC
On another thread you suggested that I should be careful with bleach with copper in the water. Is the CYA or sodium hypochlorite that I need to worry about? If it is any of these, wouldn't bromine be a better option?


TFP Expert
Platinum Supporter
May 23, 2015
Tucson, AZ
It's any oxidizer that you have to worry about be it chlorine, bromine, ozone, etc., . Cooper in water is a complicated ionic species with two different oxidation states, multiple points of stability and instability (meaning it either stays in solution as an ion or it scales out all over your pool walls) and is affected noticeably by the overall chloride ion content in solution. So there's no easy or simplistic rule of thumb that says if you have X amount of copper at Y pH value then things are good or bad. The best that can be said is having NO copper is better than any copper at all.

With all metal ions you want to avoid spiking the FC or bromine levels too high or too quickly AND/OR allow the pH to get too high. Basically high pH, high FC and high temperature are all bad in terms of causing metal ion scale.

How easily can you keep your swim spa's pH down at or below 7.5? Do you have to add acid frequently? Knowing the full set of water parameters will help -

If you can't exchange some of the water in the spa (I realize it's a lot of water to dump), then you might consider temporarily using a metal sequestrant (look up Jack's Magic product line for copper and scale inhibitor) until such a time as when you can dump the swim spa. I'm only cautioning you because there's no easy answer here, the spa store led you down the wrong path and I don't want you to think that switching to chlorine or bromine is going to be the way to go. Metal scale is a royal PITA to get rid of (copper especially) and you want to avoid it all costs.