Bromine to the rescue

[SteveOL]

Howdy all. So after 10 months of purging, cleaning, testing for bacterium at a lab, avoiding the hot tub and suffering from itching when I did hop in, last night I went to a friend’s place and tried his bromine sanitised hot tub.

 

NO ITCHING!!

 

I’m so relieved but disappointed I have barely been able to use our 14 month old tub for the past 10.

 

So I have a new bromine floater and am going to get the other chemicals I need.

 

a) Do I need to empty the spa? It is well balanced and I used the dichlor/bleach method. Cleaned and purged very recently.

 

b) I believe I need granular bromine to establish a bromine bank. My store has a product with 

1-bromo-3-chloro-5,5-dimethylhydantoin. Not strictly sodium bromide. Is that ok?

 

c) I need bromine tablets for the floater. The store’s tablets are the same chemical. Ok?

 

d) Can I use 13% liquid chlorine to shock it weekly? Also have 37.2% dichlor and some 60% dichlor. Although I’m s*** scared of chlorine now, I believe it converts the bromide to bromine and the chlorine is gone almost straight away. (1650L or 436 gal tub). Prefer not to waste it if I can use it.

 

e) Am I able to use my liquid test kit and multiply the FC result by 2.25 to get the bromine reading?

 

f) Not sure if it matters but I have an ozone generator. I’ve read that may reduce the amount of bromine I need to add.

 

g) Should I be concerned about any residual chloramines in the tub water when I introduce bromine?

 

 Thank you all. 

[waterbear]

11 hours ago, SteveOL said:

Do I need to empty the spa? It is well balanced and I used the dichlor/bleach method

No.

11 hours ago, SteveOL said:

My store has a product with 

1-bromo-3-chloro-5,5-dimethylhydantoin. Not strictly sodium bromide. Is that ok?

No, it is a one step bromine product that contains both bromine and chlorine bound to a dimethylhydantoin (DMHD). It only contains a small amount of bromine and is mostly chlorine and is not really practical for establishing a bromide reserve.

11 hours ago, SteveOL said:

The store’s tablets are the same chemical.

All bromine tablets are this chemical. It is mostly chlorine to oxidized the bromide bank and to help replenish the bromide reserve. It can takes weeks of use for either tablets or the one step product you mentioned above to establish a bromide bank and until that happens you have a chlorine spa. It's not an I issue as long as you are maintaining adequate sanitizer levels of 4 to 6 ppm total bromine. Even if the only sanitizer present is chlorine you are fine as long as you are at 5 to 6 ppm  for bromine.

11 hours ago, SteveOL said:

Can I use 13% liquid chlorine to shock it weekly? Also have 37.2% dichlor and some 60% dichlor.

The liquid is fine as is the 60% dichlor.  37.2 is a strange percentage for dichlor. What else is in there? Chlorine is a necessary part of bromine chemistry and as long as you have established your bromide bank you will have bromine and not chlorinevin the tub.

11 hours ago, SteveOL said:

Am I able to use my liquid test kit and multiply the FC result by 2.25 to get the bromine reading?

Yes

11 hours ago, SteveOL said:

Not sure if it matters but I have an ozone generator. I’ve read that may reduce the amount of bromine I need to add.

No you still need 4 to 6 pom bromine. Ozone is not residual and only sanitizes the water where it is injected. It can also deplete the bromide bank by oxidizing the bromide to bromate, which is not reversable. 

11 hours ago, SteveOL said:

Should I be concerned about any residual chloramines in the tub water when I introduce bromine?

No

[SteveOL]

No doubt about you, @waterbear. You’re a champion. Thank you. 

[waterbear]

Borax is a good additive but it seems to be used as a filler in this product since borax is cheaperctgsn dichlor.

[SteveOL]

Ok @waterbear. So I measured my bromine levels this morning with just tablets in there. About 2ppm. Thought I'd give the crushed tablets a go to get the bromine bank up as I can't get sodium bromide granules. 100g of 65% bromine in the tablets. Measured this evening and bromine is through the roof. Is that sodium bromide it's measuring? If I shock it with liquid chlorine would that bring it down? As in turn it to bromine? I'm trying so hard and am over this tub. I wouldn't be that unhappy if a tree fell on it.

[waterbear]

12 hours ago, SteveOL said:

So I measured my bromine levels this morning with just tablets in there. About 2ppm

You should have ooened the floater more and retested in 24 hours.

12 hours ago, SteveOL said:

easured this evening and bromine is through the roof. Is that sodium bromide it's measuring?

NO, you don't measure sodium bromine, you measure hypobromous acid (bromine sanitizer) when testing. You have not added any sodium bormide to the tub but have added bromide ions as the tablets dissolve. What you have done is shocked the tub. Leave the tub uncovered and let it circulate until the bromine level drops below 10 ppm and you can use the tub.

12 hours ago, SteveOL said:

If I shock it with liquid chlorine would that bring it down?

NO, it will raise your bromine level even more! Chlorine source doesn't matter and realize that that your crushed bromine tabs are mostly chlorine!

Read (or reread) this:

https://www.poolspaforum.com/forum/index.php?/topic/53410-how-to-use-bromine-3-step-method/

 

[SteveOL]

1 hour ago, waterbear said:

NO, it will raise your bromine level even more! Chlorine source doesn't matter and realize that that your crushed bromine tabs are mostly chlorine!

Thanks for that. I’ve read it alot. I’ve been working hard to understand the tub, chlorine and now bromine. 
 

So even when the tablets are 65% sodium bromide and 28% chlorine, chemically there’s more chlorine than bromide?

[waterbear]

they are not 65% sodium bromide. Bromine tablets are (depending on the brand) either a combination of 1-bromo-3-chloro-5, 5-dimethythydantoin 60%, 1,3-dichlor-5, 5-dimethythydantoin 27.4%,  and 1,3-dichlor-5-ethyl-5-methythydantoin 10.6% or they are 1-Bromo-3-chloro-5,5-dimethylhydantoin 98%

They are organic forms of bromine and chlorine and a slower to release bromide ions than the inorganic sodium bromide, which dissociates completely as soon as it dissolves into sodum and bromide ions. Bromide ions need to be oxidized into hypobromous acid (your bromine sanitizer by either hypochlorous acid (which all chlorine sources form once dissolved into water) or another oxidizer such as Potassium Monopersulfate (MPS) aka non chlorine shock. The chlorine bound to the dymethylhydantion molecure is also released more slowly than inorganic chlorine (bleach or cal hypo) much in the same way that the organic chlorinated isocyanurates dichlor and trichlor are also not 100 available, depending on the amount of CYA present.

The combination tabs have almost 63% of the available halogen as chlorine and, IMHO, are more effective since the bromide bank, once established, stays fairly constant and it is the oxidizer (chlorine) that gets consumed activating it.

The single chemical formulations provide about 65% bromine and 29% chlorine and, IMHO, require shocking more often but, also IMHO, might be useful in conjunction with ozone since ozone has a tendency to over oxidize the bromide into bromate which cannot be regenerated and is therefore essentially lost as a useful component of the sanitizer system. (This is conjecture on my part based on my understanding of chemistry of bromine in a hot tub).

Realize that the halogens are chemically bound to the DMHD molecule and are not 100% available to react chemically so those percentages are a bit misleading.

The purpose of the bromine is to create bromide ions which are then oxidized into hypobromous acid by an oxidizer, usually chlorine. IF there is more bromine than chlorine it just means that there are more bromide ions that can be oxidized but how many are oxidized is a function of the amount of oxidizer present.

 

[SteveOL]

1 hour ago, waterbear said:

 

they are not 65% sodium bromide

 

Well there you go.

 

You understand my confusion then when the label reads “650g/kg available bromine and 280g/kg available chlorine present as bromochlorodimethylhydantoin”.

 

 My tub has ozone. 

 

This is going to be a wild ride. 
 

[waterbear]

47 minutes ago, SteveOL said:

present as bromochlorodimethylhydantoin

says nothing about sodium bromide.

[SteveOL]

Mate. I’m a geologist. Not a chemist. I’m just trying to understand. I realise my questions are probably annoying but if you could try to not make me feel like a complete idiot I’d really appreciate it. 

[waterbear]

Not trying to make you feel like an idiot. Just trying to explain things in simple terms. Since you are a geologist think of it as explaining to someone how calcite, vaterite, and aragonite are all calcium carbonate crystals yet have different crystalline structures and form under different geologic conditions.  

[waterbear]

Just take a deep breath. It's not that hard, I promise! Once you get over the learning curve you'll wonder why you ever found it confusing.

Bottom line, if you don't have sodium bromide then just use your granular product for the first two weeks daily after a  new fill and maintain 4 to 6 ppm bromine then put the floater and tabs in and adjust the floater to maintain the bromine level at 4 to 6 ppm. When adjusting the floater give it 24 hours to stabilizer. Shock weekly with chlorine (diclor  or bleach) and let the bromine drop below 10 ppm before entering tub.

Don't test pH or TA when bromine is 10 ppm or higher, it won't be correct

https://www.poolspaforum.com/forum/index.php?/topic/58991-false-high-ph-readings-when-shocking-some-truths/

and TA between 50 to 70 ppm for best pH stability.

https://www.poolspaforum.com/forum/index.php?/topic/52522-some-truths-about-ph-and-ta/Keep pH around 7.8 to 8.0

CH 130 to 200 is fine. If your fill water is over 400 ppm CH then consider adding a sequestrant to help prevent scale formation.

drain and refill every 3 to 4 months.

[SteveOL]

That's outstanding. Thank you very much. I do appreciate you going to the trouble to explain.