2 quick questions... (yeah right)

[pitguy3]

1. My Father has just purchased a new Hot Tub(HT) and was told that using Chlorine in it would not be cost effective since the chlorine will decrease quicker in hot water. Is this a true statement??

2. He is currently using Bromine (sp?). He states that the Pool Calculator does not calculate Bromine. Where can he find the calculations to increase the amount of bromine in his HT since he also states that the container does not provide any help??

Trying to make it where he does not fall into the Pool/HT store trap and spend too much $$$!!

Thanks in advance!

 

[chem geek]

Chlorine only gets depleted faster from it outgassing faster if there is no Cyanuric Acid (CYA) in the water. For the FC/CYA levels we recommend for spas, which is roughly an average 2-4 ppm FC with 30-40 ppm CYA, the daily chlorine demand without an ozonator and no bather load is around 25% and chlorine loss rates are roughly the same if not lower than bromine. If you have an ozonator, then chlorine demand without bather load can double to 50% or more. Also, with chlorine one doesn't have "tabs" as with bromine so one needs to add chlorine every day or two. These are reasons why for those who don't soak every day or two that bromine is less maintenance than chlorine.

How often is your father using the spa and does the spa have an ozonator?

To calculate bromine from chlorine, just multiply by 2.25. Likewise, to convert from bromine to chlorine, divide by 2.25. So if he wants to increase bromine by 4 ppm, for example, then he can just use The Pool Calculator with an FC of 4/2.25 = 1.8 to figure out how much bleach to add to oxidize bromide to bromine (assuming he has already set up a bromide bank by initially adding sodium bromide).

 

[GuinnessPhish]

So if he wants to increase bromine by 4 ppm, for example, then he can just use The Pool Calculator with an FC of 4/2.25 = 1.8 to figure out how much bleach to add to oxidize bromide to bromine (assuming he has already set up a bromide bank by initially adding sodium bromide).

If you haven't set up a bromide bank by initially adding sodium bromide, it can also eventually develop by using about 6 tabs over a period of time?


Just making sure I understand completely: If your bromine reading was about 2.25, you'd want to get it up a little to around 4 - 6? And you could accomplish this simply by adding a certain amount of bleach? You don't need to add another tablet to the floater?

 

[chem geek]

Yes, using bromine tabs will eventually build up a bromide bank. The usual sodium bromide dosing is 1/2 ounce per 100 gallons which comes to roughly [EDIT] 30 [END-EDIT] ppm (in bromine units). Typical bromine tabs are 1" BCDMH, but I don't know their weight. If they were 1/2 ounce, then being 66% available bromine one tab in 350 gallons would be 10.7 ppm bromine. So you are right that for a typical sized tub 6 tabs should build up a decent bromide bank.

As for the appropriate background level of bromine, figure that a minimum chlorine level is 1-2 ppm so this corresponds roughly to 2-4 ppm bromine. 6 ppm is probably higher than you'd want for a background level since people often don't like the smell of bromine or bromamine (it smells different than chlorine or chloramine). And yes, you just add an oxidizer (bleach, Dichlor, MPS, etc.) to reactivate bromide to bromine. The reason for adding tabs is to provide a background level of bromine, but it usually isn't enough to handle bather waste from bather load unless you infrequently use the spa and don't soak for very long. You generally have the tabs in to maintain bromine in between soaks, but add an oxidizer after a soak to oxidize the bather waste.