Very High Bromine and Purple pH indicator

[wayner]

I am having weird test results with my spa - it uses bromine to sanitize.

I have a Taylor K-2006 Chlorine pool test kit with the FAS-DPD chlorine test. I recently purchased refill reagents so they aren't too old. With a 10mL sample for chlorine it takes 32 drops to neutralize from red/pink to clear. This would indicate a Bromine level of 32*.5*2.25=36 (the 2.25 is the multiplier to use for bromine - or so I have been told). I have been in the spa myself and I have survived and the water doesn't seem too abnormal. My skin does smell like bromine afterwards but not excessively so.

When I try to test the pH when I first put in a couple of drops and the sample turns orangey-yellow like pH is too low. But after putting in all five drops it turns a bright purple. My understanding is that high bromine/chlorine can screw up this test and cause the purple colour.

I am not sure why the bromine is so high. I have a tube dispenser for small bromine tablets that goes in my filter and I had this at its normal setting of slightly open - just like for the last nine years since I have owned the spa. Over the last few days I have shut this off completely so that there is no bromine exposed to the water to try to lower the bromine. The only difference is that the spa has not been used very frequently over the last couple of months.

Any advice on what I should do? Should I drain and refill? Are there any other options?

 

[JVTrain]

The high bromine is causing the high pH result.

I suspect that with very little use (bather waste) combined with the tube dispenser still likely giving off some bromine even though it is shut off completely is keeping the bromine high. Remove the bromine dispenser tube entirely and then observe your bromine levels.

Just for curiosity, how long since you last changed the water?

 

[wayner]

Thanks - I did that and will keep an eye on the levels.

 

[JoyfulNoise]

What is the primary component of the tablets - DBDMH (dibromodimethylhydantoin) or BCDMH (bromochlorodimethylhydantoin)? Are any oxidizers (chlorine or MPS) being used? Do you have an ozonator?

The chlorine in the BCDMH will get into your water as hypochlorous acid which will oxidize any residual bromide in the water to bromine. The same is true for any external source of oxidation. You have a bromide bank in the water, so any oxidizer will convert that to bromine.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006

 

[wayner]

The tablet container says (this is SpaBoss Brominating Tablets):
Available Bromine: 64.0%
Available Chlorine: 28.0%
Both present as 1-Bromo-3-Chloro-5,5 Dimethylhydantoin and related hydantoins

I think I do have an ozonator but I am not 100% sure. The spa is a Jacuzzi, I think it is a J-315 from about 2006-7.

When you see any oxidizer will convert that to bromine, should I throw some spa shock in?

 

[JoyfulNoise]

The tablet container says (this is SpaBoss Brominating Tablets):
Available Bromine: 64.0%
Available Chlorine: 28.0%
Both present as 1-Bromo-3-Chloro-5,5 Dimethylhydantoin and related hydantoins

I think I do have an ozonator but I am not 100% sure. The spa is a Jacuzzi, I think it is a J-315 from about 2006-7.

When you see any oxidizer will convert that to bromine, should I throw some spa shock in?

If you throw spa shock in, it will likely raise your bromine levels further.

Joel's advice still holds - take the floater out and let the bromine levels come down. See where they land. My post was simply to make a chemical argument for how your bromine levels got so high.

Your brominating tablets contain both a source of bromine AND an oxidizer (chlorine). Therefore, they are capable of raising your water's bromine levels all on their own. Your water has bromide in it. That is what happens to bromine when it kills pathogens - bromine turns into bromide. So, when you add any kind of spa shock or oxidizer to the water (eg - dichlor, MPS or ozone) you will convert the bromide back into bromine.

So it sounds like the lack of use coupled with brominating tablets and, possibly, a continuos oxidizer source (ozone) has lead you to where you are today - high Br.

 

[wayner]

To close the loop on this - I took out the bromine dispenser on Dec 22. I measured several times and it was still fairly high for several days. I forgot to test for a few days and on Jan 2 it was down to zero and the water was slightly cloudy/yellowy. So I added a bit of shock and put the dispenser back in and a day later it is good - the reading is 6.3 or 14 drops in a 25mL sample (14*.2*2.25). The pH is still a bit low at 7/1 and the TA is only 30 so added some TA up chemicals which also tend to increase the pH.