Weekly Shock Lowers Ta

[mzimm]

I'm just getting comfortable with balancing my water and have found my perfect TA - here is my numbers TA=60, PH=7.6, CH=180, Borates=50. I'm using Brilliance for Spas Bromine system and maintain my Bromine levels at 2-2.5 ppm.

Each week I use the Brilliance Oxidizer which is potassium monopersulfate. I'm only using about .250 oz (1/2 tablespoon) for my 230 gallons of water. But the next day I check my water balance and the ph is at 7.2 and TA goes down to 50.

Question is should I do a weekly shock (spa is used my my only once each day for 20 minutes per use)? If I should shock should I be using something else that wouldn't mess up the water balance so severely?

Thanks,

Mike

[chem geek]

MPS is acidic so lowers both pH and TA, but some brands of non-chlorine shock are more pH buffered so would have less of an effect on pH. Of course, it's easy to just add some baking soda to raise the TA as needed.

As to whether you need to shock or not, that depends on your specific situation. You can try not shocking and see if your regularly maintained bromine level is sufficient to take care of your bather waste, keeping the water clear. For those using the Dichlor-then-bleach method, they rarely need to shock, but I'm not so sure whether it's needed for bromine. It probably depends on how clean you are when using the spa and whether bromine is able to handle whatever it is that you are introducing into the water during a soak.

If you don't shock with MPS, then you will likely need to increase the amount of bromine you need to add, unless you have an ozonator.

[quantumchromodynamics]

I don't think that shocking is always necessary. It would help if there was a test for bromamines, like there is for chloramines. However, bromamines are good sanitizers and oxidizers, so they are not the same issue as chloramines.

You could use regular, unscented 6 % bleach to shock instead of MPS.

You could keep the pH and Total Alkalinity higher to reduce the total number of times you have to adjust them.

If you keep the pH at 7.8 and the TA at 70, then they will still be OK after shocking. You will still need to add baking soda to compensate for the acidity of the MPS, but less often.

[mzimm]

I don't think that shocking is always necessary. It would help if there was a test for bromamines, like there is for chloramines. However, bromamines are good sanitizers and oxidizers, so they are not the same issue as chloramines.

You could use regular, unscented 6 % bleach to shock instead of MPS.

You could keep the pH and Total Alkalinity higher to reduce the total number of times you have to adjust them.

If you keep the pH at 7.8 and the TA at 70, then they will still be OK after shocking. You will still need to add baking soda to compensate for the acidity of the MPS, but less often.

Thanks for the info! If I decide to use unscented 6% bleach to shock would this have less of an impact on my water balance? Also for 230 gallons how much bleach would I want to add?

Thank you,

Mike

[quantumchromodynamics]

The bleach would have less of an impact on the water balance. It should be close to net neutral as far as its effect on pH.

The general rule of thumb is to use 5 ounces of regular, unscented 6 % bleach per person hour. However, 5 ounces would raise your bromine level by about 23.6 ppm.

You're going to have to experiment a little to find the right amount for your tub. You want to keep the bromine between 1.0 and 5.0 ppm at all times. You can go a little bit above 5.0 when shocking, but I wouldn't go too much above that.

A good indicator is how much bromine you have the next day before you use the tub again. Ideally, you want the level to be about 2.0 when you are ready to use the tub and you would add the bleach after using the tub.

The bromine tabs are going to make up part of the demand, so that will reduce the need for shocking.

Try adding 2 ounces of bleach after using the tub and then test the bromine level a few times before the next time you use the tub to see what the bromine level does over time.