Shocking with bleach instead of MPS - Have a few questions!

Jump to latest Follow Reply
M

michy

0
Sep 26, 2009
19
N.B. Using 3 step bromine system. 370 gal tub. Testing with K-2106 test kit.

First question, for those that use MPS to shock/oxydize your tub, how much are you using and how often and how long before it is safe to go in the tub? The instructions on my container say 125g/fresh fill per 1000L. 30g per day. It has always taken a couple days before bromine levels are in safe range.

That being said, I have decided to try shocking my bromine tub with bleach instead of MPS, since there are a lot of clear instructions on this forum. I am following waterbear's procedure and using the pool calc.

Second question
I balanced the water - TA 80, PH 7.2, CH 170 and then added the liquid sodium bromide and then shocked with 150ml 10% bleach. The next day, the pH was through the roof - 8+ and burned and dried my skin, when I dunked my hand in to test, which I know it is because the pH is high but the water never felt that way after I shocked with MPS. I've gotten the pH down to 7.6 and the TA to 70 but based on what I've read in similar posts, I'm going to try to lower it to 50 (50 has always been my water's sweet spot) and get the pH down to 7.0 and aerate. At 7.6, I still feel the water leaves a dry feeling (it used to feel silky) but it's not burning any more. If I get the pH and TA down more, do you think the water will feel less drying to the skin? I really hate the feeling.

Third question
Once I get the pH and TA where I want it, should I add boric acid to help lock in the pH? Can you use it with a bromine system?


Fourth question
Anyone notice a difference with bleach shock when testing the bromine using the Taylor kit? With MPS, the water goes from pink to completely clear, but with the bleach, the water goes from pink to light light orange. I tried adding tons more drops to see if it would go clear but it never does.
 
Re: Shocking with bleach instead of MPS - Have a few questio

I don't have a spa, but the general rule-of-thumb for how much oxidizer it takes to handle bather waste in a hot (104ºF) spa is that every person-hour requires around 3-1/2 teaspoons Dichlor or 5 [EDIT] fluid ounces [END-EDIT] of 6% bleach (or 3-1/2 [EDIT] fluid ounces [END-EDIT] of 8.25% bleach) or 7 teaspoons of non-chlorine shock (43% MPS). This is when there is no ozonator. With an ozonator the amount needed may be around half as much though depends on the strength (runtime) of the ozonator.

The initial MPS dosing you described on a fresh fill is equivalent to 25 ppm FC (56 ppm bromine) while the daily dose is equivalent to 6 ppm FC (13.5 ppm bromine). This does seem pretty high. I don't think you need to shock on a fresh fill and can just add enough for a bromine level of 4-8 ppm. Then, the amount of oxidizer you add after a soak is whatever it takes to maintain a bromine level and still have some for the start of your next soak.

MPS is net acidic while bleach will raise the pH when added. Normally the pH would drop back down as the bromine gets used/consumed, but with the TA at 80 ppm, carbon dioxide outgassing causes the pH to rise. If you want to use bleach instead of MPS, then you should get your TA down much lower, probably down to around 50 ppm. As an additional pH buffer that doesn't cause the pH to rise, you can use 50 ppm Borates (from boric acid) and yes, you can use that in a bromine system. This is similar to what is done with the Dichlor-then-bleach method, but also applies to bromine. If you are using bromine tabs, then those are also net acidic so perhaps the TA may not need to be lowered to 50 and instead 60 ppm might work, but you'll just have to see what TA has the pH be more stable.

As for feeling drying to the skin, I don't know. It's most likely the pH since that's the main difference, so your plan sounds reasonable.

As for the Taylor kit going from pink to light light orange instead of clear, I'm not aware of why that would be the case. That's a good question for Taylor so if you find out the answer, please let us know. The bromine should be the same from MPS and from chlorine. What bleach are you using? Perhaps there is some additive causing this small interference.
 
Re: Shocking with bleach instead of MPS - Have a few questio

Thanks Chem Geek. I added baking soda to get the pH and TA down. The latest numbers are: pH 7.6, TA 50. The water feels much better, so I'd consider that problem solved. The bromine test now goes completely colorless, so I'm going to guess the high pH had something to do with it. It's the only thing I can think of. (FYI though - the bleach I'm using it UltrAqua (Made in Canada). 10.8% sodium hypchlorite.. Available chlorine content is 10.3%.)

A few follow up questions. I bought a box of borax. I couldn't find boric acid at the hardware store. I was looking for it in liquid or powder form alongside the insecticides. According to the pool calc, I would add 618 g of borax + 307 ml of muriatic acid (1400 Litre spa). Would I add it now? I guess I would check my TA and pH after and adjust if necessary?

And now that my TA is lower, if i continue to use bleach instead of MPS, should I see the pH go higher than 7.8 after adding it? If you say it will go down as the bromine gets used, it still needs to be at a safe level before getting in the hot tub, so I would need to use acid to bring it down? What's a normal jump in pH after adding bleach? With borates? Without borates?

My last question is can I use bleach and MPS interchangeably to oxidize, on the same fill? The reason I ask is that if I decide to switch completely to bleach, I will lose out on soaking days with my kids, while I figure what I'm doing and get the water balanced after adding bleach.

Thank you in advance for your patience and great help on this forum.

Michy
 
Re: Shocking with bleach instead of MPS - Have a few questio

Yes, you could add the Borax and acid now -- split up the dosing in part so some Borax, some acid, mix, repeat. That will lessen the swing in pH in the spa. If you end up with the pH near 7.5, then you'll probably find that the TA measures either 55 or 60 ppm and that is fine and no need to lower it.

The pH won't go up as much when adding bleach due to the borates in the water. Adding 5 ppm FC of bleach (for 11.2 ppm bromine) would only raise the pH from 7.5 to 7.64 (that's with CYA in the water; with no CYA it would rise to 7.59) so you shouldn't see much pH swing from using the bleach. Without the borates, the pH jump (with CYA) would be to 7.91 so quite a bit higher.

You can use bleach and MPS interchangeably, BUT realize that MPS is acidic so will lower both pH and TA. So if you use it regularly, you'll need to watch both pH and TA to make sure they don't get too low. Technically you'd want to compensate by adding a pure base, but we don't have that (people don't add lye to their pools or spas). You could add Borax, but if you use MPS regularly that would raise the borates too much. So you probably would need to use pH Up (sodium carbonate) if you need to raise both the pH and TA or use baking soda if only the TA needs to be raised. It's hard to know what you'll need because it depends on aeration and outgassing. Just watch the pH and TA since you don't want the TA to get wiped out since it's the main buffer preventing the pH from crashing downward from MPS (or any other acid).
 
Re: Shocking with bleach instead of MPS - Have a few questio

I didn't know you could get a PH jump by adding chlorine to our bromine spa. I add 1-2 teaspoons of granular chlorine when we use the tub to give it a bump. but i'm always fighting PH and TA drop because of the bromine tabs. I use granular chlorine 90% of the time. I may switch to liquid bleach when I run out of granular but that may take another year or two lol. we throw it in before we get in and then just let it air out for 20 minutes after we get out.

I haven't tried boric acid yet but i'm thinking about it.

if you shocked to 56 ppm bromine on a fresh fill it will take a while for that to come down, like a few days. you can shorten the time by leaving the spa open and letting the sunlight destroy the bromine for a few hours. I went from 60ppm to around 10ppm, but I don't remember how many hours it took. maybe about 4-6 but i'm also in florida. I like to shock to 25ppm but messed up and shocked it to 40-60ppm a few times.

I have the taylor 2106 too and when bromine is threw the roof it doesn't want to go clear.
 
Re: Shocking with bleach instead of MPS - Have a few questio

michy said:
I added baking soda to get the pH and TA down.
Click to expand...
Note that baking soda raises pH and TA when the pH is less than 8.3. If the pH is over 8.3, then the pH will be lowered by baking soda.
 
Re: Shocking with bleach instead of MPS - Have a few questio

Yes, baking soda is sodium bicarbonate and the bicarbonate is both an acid (as it can release a hydrogen to become carbonate) and a base (as it can accept a hydrogen to become carbonic acid). The halfway point between being an acid and a base is at a pH of 8.2 (8.3 if one ignores ionic strength though in water with 300 ppm CH it's 8.0 due to a calcium carbonate ion pair).

Of course, using baking soda to either raise or lower pH is foolish since it mostly raises the TA and that is its primary purpose.
 
Re: Shocking with bleach instead of MPS - Have a few questio

pooladdict said:
Baking Soda can lower PH once its over 8.3???? really Richard?
Click to expand...
Just to be clear, I was mainly correcting the poster's claim that they used baking soda to lower pH. I included a technical exception where pH would be lowered by baking soda.

In any case, baking soda would never be used to lower pH in a pool.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Re: Shocking with bleach instead of MPS - Have a few questio

In any case, baking soda would never be used to lower pH in a pool.
Click to expand...
+1 what JamesW (and chemgeek) just said.

Borax (up) and muriatic acid(down) are all you need to adjust pH. Baking soda's sole purpose in the TFPC method we teach is to adjust TA upward without affecting pH.

(Uh, I think there is a clause in the TFPC method that allows folks to also use baking soda to make a REALLY nice cake and send us Mods all a large slice so I may have misspoke :roll: :roll: )
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply