Bromine chemistry & bleach

[PoolDiver]

After reading the advice here, I attempted switching to bleach as a shocking agent for my 19,000 gal indoor gunite pool which uses bromine for sanitation. I used http://www.thepoolcalculator.com/ with TFP suggestions and 15 FC goal from a base of 0 (I'd used Oxone-based shocks before so there was no measurable FC). That required 6 jugs of 6% bleach.

After the shock, there was intense chlorine odor in the pool room for days, something I haven't experienced with Ca-hypo or Li-hypo shocks. I'm wondering whether this is normal or a sign that something didn't go according to plan.

 

[JamesW]

The intense chlorine odor suggests that there were organic compounds that were not being effectively oxidized.

If you have been on bromine tabs for a while, there might be excessive levels of DMH (the carrier compound for the bromine, which is analogous to the cyanuric acid in trichlor tabs). High levels of DMH can reduce the effectiveness of the bromine.

How many total pounds of bromine tabs have been used?

Bromine chemistry problems can be complicated. What other information can you tell us about the pool? Things such as usage, filtration, pH etc.

 

[PoolDiver]

The intense chlorine odor suggests that there were organic compounds that were not being effectively oxidized.

I had not experienced the same smells with Ca-hypo, Li-hypo or Oxone-based shocks, which why I was surprised.

If you have been on bromine tabs for a while, there might be excessive levels of DMH (the carrier compound for the bromine, which is analogous to the cyanuric acid in trichlor tabs). High levels of DMH can reduce the effectiveness of the bromine.

Pool's been in operation for over a decade using Br tabs.

How many total pounds of bromine tabs have been used?

Right before I tried the bleach shock the pool hadn't been actively used for 2+ months. It stayed covered much of that time. Several pounds of tablets much have been used since the previous shock which was with Oxone.

Bromine chemistry problems can be complicated. What other information can you tell us about the pool? Things such as usage, filtration, pH etc.

Very light use. Pool remains covered most of the time for moisture control. Diatomaceous earth filter. Pump runs 8hrs/day. Well water so there is some copper & iron.

It is possible that TA got low around that time. I got a new Taylor K-2006 kit from Amazon about then. It told me that TA was high (140) so I used an alkalinity reducer to get it in range. About 4 weeks later I did a computerized water test. It said the alkalinity was 82. I checked with Taylor. It said 120ish. I did a second computerized test and got 85 TA. I added soda to compensate and contacted Taylor to ask about the test results. They maintain their test kit should be accurate. 50% diff between computer & Taylor is a bit scary, though. I'm double-checking with Bioguard strips now and they say TA is around 120.

Let me know what water metrics you'd like to get: I have pretty much everything from the computer test.

Thanks!

 

[JamesW]

Regular bleach should not react any differently than cal-hypo or lithium hypochlorite. Some bleach is scented, and might create an unusual smell. Scented bleach should not be used, but I doubt that that is the issue.

Oxone is not a chlorine based shock, and would not create any chlorine byproducts or any chlorine related smells.

Some well water contains hydrogen sulfide, which can create a "sulfur" smell, but I doubt that that is the issue.

The long period of time using bromine tabs has likely caused an excess buildup of DMH, which might be reducing the ability of the bromine to be reasonably effective.

You might need to drain and refill to get rid of the DMH. You would probably do better using chlorine than bromine. If you do drain and refill, I would suggest that you consider switching to chlorine. A salt system would probably give you good results.

What are your FAS-DPD results for FC and CC?

Note that draining a pool can be risky if not done properly. If you're not sure that you can do it safely, then it would be best to consult with a professional before deciding whether or not to do a drain and refill.

 

[y_not]

It is possible that TA got low around that time. I got a new Taylor K-2006 kit from Amazon about then. It told me that TA was high (140) so I used an alkalinity reducer to get it in range. About 4 weeks later I did a computerized water test. It said the alkalinity was 82. I checked with Taylor. It said 120ish. I did a second computerized test and got 85 TA. I added soda to compensate and contacted Taylor to ask about the test results. They maintain their test kit should be accurate. 50% diff between computer & Taylor is a bit scary, though. I'm double-checking with Bioguard strips now and they say TA is around 120.

Trust the Taylor kit, DO NOT trust the electronic test, they're horribly off. Test strips, they're in between, don't trust them either.

Do review your testing procedure(s) in the 'Extended Test Kit Directions' post in the 'Testing & Balancing Your Water' forum (category).
Also read the parts that tell you how to tell if your reagent(s) has/have gone bad. Yes, I know it's new, but some vendors will let these sit on the shelf a long time. Or FedUPS freezes it or something.