Wait Time After Shock

[Flagstone]

We have a new 500 gallon above-ground spa, and after lurking here for awhile I think I'm starting to get a handle on the chemistry. I'm still a little confused, however, about weekly shocking.

We started the spa on bromine with a kit by "Brilliance." It consisted of some pH/alk adjustment chemicals, a pouch of metals reducing chemicals, bromine, and an oxidizer to activate the bromine. For the first couple days I had a little trouble keeping the bromine above zero for very long, but now it seems to be doing well. I'm using brominating tablets (1-bromo-3-chloro-5, 5-gobbledygook)in a floater and add 1 to 2 ounces of 6% bleach after every use. The spa also has an ozone generator that runs with the continuous filter cycle.

The vitals:

br=3

alk=80+

pH=7.5

ch=250-

The water is clear, but has a very slight blue-green tint and a touch of a musty odor. I'm about a week into it, so I figure it's time for a weekly shock. But with what? The local spa store recommended potassium peroxymonosulfate because I shouldn't use chlorine products with bromine (yes, I know this is not true ) and because we would only have to wait a few minutes before getting back in the spa. I'm leary that either the product is not strong enough to do the job or maybe we shouldn't get back in so soon. So...

1) Should I use this product?

2) or should I just use bleach (but more of it)?

3) how high should I expect my bromine level to go when I shock correctly?

4) after adding bleach (a small amount just to keep the bromine up) how long do we need to wait before getting in?

Thanks for your help!

[waterbear]

It is not true that you can reenter a bromine tub right after shocking with MPS. MPS (and chlorine) will cause the bromine sanitizer levels to rise by oxidizing the bromide ions into hypobromous acid, your active bromine sanitizer. You need to wait for the bromine levels to drop below 10 ppm before entering the tub no matte what kind of oxidizer you use.

If MPS is used with a chlorine system then you CAN enter the water about 15 minutes after using it because chlorine chemistry is different than bromine chemistry. This confuses a lot of people that really don't understand bromine chemistry.

To shock with bleach you need about 1 to 1 1/2 cup of ultra bleach or 1 1/3 to 1 3/4 cups of regular strenth bleach for a 500 gallon spa. You should shock weekly and leave the cover off and the filtration running until the bromne levels drop, usually a few hours to a day.

You want your bromine levels to go above 10 ppm up to as high as 20 ppm when shocking. Usually just above 10 ppm is sufficient.

[Flagstone]

It is not true that you can reenter a bromine tub right after shocking with MPS. MPS (and chlorine) will cause the bromine sanitizer levels to rise by oxidizing the bromide ions into hypobromous acid, your active bromine sanitizer. You need to wait for the bromine levels to drop below 10 ppm before entering the tub no matte what kind of oxidizer you use.

If MPS is used with a chlorine system then you CAN enter the water about 15 minutes after using it because chlorine chemistry is different than bromine chemistry. This confuses a lot of people that really don't understand bromine chemistry.

To shock with bleach you need about 1 to 1 1/2 cup of ultra bleach or 1 1/3 to 1 3/4 cups of regular strenth bleach for a 500 gallon spa. You should shock weekly and leave the cover off and the filtration running until the bromne levels drop, usually a few hours to a day.

You want your bromine levels to go above 10 ppm up to as high as 20 ppm when shocking. Usually just above 10 ppm is sufficient.

Thanks for the help, Waterbear! Just a couple more questions:

1) So the main thing to watch before getting back in after a shock treatment is the bromine level? That is, we can get in soon after doing a small shock with bleach or MPS as long as the bromine level doesn't go above 8 to 10 ppm, right?

2) When shocking with MPS (potassium peroxymonosulfate) do I still need to drive the bromine to >10 ppm or does the MPS provide enough additional shock/sanitizing on its own that the bromine can stay lower? I guess it's a question of whether the MPS is immediately consumed by the bromine conversion or whether some stays in the water as a sanitizing agent. I added 4 ounces (the instructions recommend 2 to 4 oz.) last night after we got out and the bromine went from 2 to 8 ppm.

Again, thanks for you help. I've been to at least four local pool/spa stores and so far all of them have been wrong on at least one (but usually more) aspect of using bromine. It's a wonder anyone around here can maintain a healthy spa.

[waterbear]

MPS is an oxidizer only. It is NOT a sanitizer. It's purpose in a bromine system is to oxidize the bromide ions into hypobromous acid. Shocking meand raising the bromine levels high enough to burn of organics in the water by raising the bromine levels above 10 ppm. This is done by adding enough oxidizer, whether MPS or chlorine, to convert the bromide ions into hypobromous acid.

In a chlorine system MPS works differently. It stays as a residual in the water to oxidize organics before they form choramines. It does not break down chloramines that are already in the water. It also cannot oxidize chloride ions into hypochlorous acid, the active chlorine sanitizer.

It's a case of comparing apples and oranges to try and compare how MPS works with chlorine vs. bromine.

If you are using a 2 step bromine system (no tablets) then you would add your oxidizer on a regular basis to maintain the 4-6 ppm bromine level and shock it weekly with a larger amount of oxidizer to burn off the organics with the higher bromine levels created.

In a 3 step bromine system (with tabs in a floater) the tabs are what keeps the bromine levels at the 4-6 ppm range (they contain both bromine and chlorine) and you still need to shock weekly with additional oxidizer to burn off organics.

The three step bromine system is much easier to maintain, IMHO.

[Flagstone]

Ok Waterbear, thank you very much for your help!