MPS in a Bromine Spa?

[heykerrdog]

I'm trying to understand the use of MPS in my bromine spa versus using bleach. I am hoping that by using MPS instead of bleach it will eliminate some of the smell.

From the research, I can't tell if it's advisable and/or suitable to use MPS instead of bleach for daily maintenance. I only see statements about shocking with MPS.

From some of the posts, it seems like some people use MPS maybe once a week to shock their spa, but I'm not sure if they are using MPS after each soak.

The Pool Math Calculator doesn't show MPS in the FC calculation so I can't figure out how much MPS to use to get the Br- target I want.

Can I use MPS instead of bleach after each soak?

So far, this is what I've found regarding MPS:

1. It is not a sanitizer.
2. It adds sulfates.
3. It does not have any CYA.
4. It is net acidic.
5. It will lower pH and TA.
6. 7 teaspoons MPS per person/hour of soaking.
7. It activates bromine.
8. It reactivates used-up bromine.

I've read that by using MPS it allows you to use the spa sooner than if you use bleach to activate the bromine. I don't understand why.

Can somebody tell me the MPS story?

As always, thanks for all your help.

Happy 4th of July, too!

 

[chem geek]

You can use any oxidizer to make more bromine in a bromine spa, assuming you have a bromide bank either by initially adding sodium bromide to the spa or by continued use of bromine tabs.

You can use MPS instead of bleach after each soak, but it probably won't do anything for the smell. You probably just don't like the smell of bromine or possibly bromamines. Usually people using MPS after each soak need to shock with chlorine once in a while because bromine and MPS won't oxidize all the same bather waste that chlorine will.

It is not correct that MPS lets you use the spa sooner than chlorine. First of all, you don't use the spa right away when you dose with any oxidizer after your soak because the bromine level will be quite high if you've been soaking for a while (or with more than one person). The difference in chlorine vs. MPS for creating more bromine is that chlorine reacts with bromide very quickly to produce bromine while MPS takes longer so the MPS can react with some of the bather waste to oxidize it instead of having bromine do so. In theory this might result in fewer bromamines so less smell, but in your case that doesn't seem to be happening.

If you are soaking with more than 2-4 ppm Total Bromine, then you should try targeting less bromine for the start of your soak. That should reduce some of the smell during the soak if it's due to bromamine formed from your sweat and urine (yes, there's urine even if not intentional).

 

[heykerrdog]

I started out last night at 8:00 pm with 2.5 ppm Br-. The spa party ended at 11:00 pm. 4 adults in and out at different intervals. We calculated 5.7 person hours.

7 tsp./person/hr = 40 tsp. MPS

At 06:30 this morning my Br- is through the roof--too high for the drop test to measure. The drop test turned from red to orange above 30 ppm Br- and won't turn clear.

The MPS bottle has different dosage recommendations. It says 1 1/2 - 2 oz. per 500 gallons every week for heavy bather loads. For lighter bather loads 1 1/2 - 2 oz. per 500 gallons every 2 weeks.

Ugh. 4th of July and my spa is unusable.

 

[chem geek]

40 teaspoons of MPS in 450 gallons would create the equivalent of 30 ppm FC or 68 ppm bromine.

Does your spa have an ozonator? Was the spa hot at 104ºF (people can't generally stay in that hot a spa for more than around 20 minutes)? It takes 24 hours for the oxidation of bather waste to nearly complete though most should be in the first 8 hours, but chlorine is a faster oxidizer than bromine.

The rough rule-of-thumb only applies to spas without an ozonator (with an ozonator less than half the amount is needed and for bromine with an ozonator even less than that) and where the person-hour calculation is with the water hot (i.e. more sweating) and it was also based on chlorine spas though it should take the same amount for bromine but the bromine may take longer to oxidize the bather waste.

Leave your spa uncovered and the bromine level will come down. If you want to lower it more quickly, you can add a reducing agent (like ascorbic acid or citric acid) or dechlorinator (sodium thiosulfate). Though hydrogen peroxide can be used to reduce chlorine, I don't think that will work with bromine (since it could oxidize bromide to bromine).

The MPS bottle recommendation doesn't define "heavy bather loads" and 2 ounces would be 12 teaspoons so only a little more than one person-hour of soaking. What you should do is determine specifically what is needed for your spa. If you've been using it before, you should have had some idea of how much oxidizer is needed to still have a residual of bromine 24 hours later -- that's the real rule to follow.

 

[heykerrdog]

Thanks again, chem geek!

We run the spa at 99 degrees.

Well, I jumped in it with my wife at 0630, knowing we were "feeding" the beast as sacrificial lambs. I briefed her on the high Br- level and we were making it a brief experimental try. It destroyed her swimsuit top. Let that be a lesson to her to wear clothes in the hot tub. I immediately peed in it, (I didn't brief her on that part). The whole spa turned yellow green, I started laughing and jumped out. Fastest I've ever seen her exit the spa. We jumped in the shower. It's 12:30 and we're still alive

I left the cover off. Ran the pumps and jets. Left it open. Rode the bicycle to the Huntington Beach 4th of July parade.

6 hrs. later, readings now that it's been properly fed and rested:

Water is crystal clear
Br- = .5
pH = below 7.0. Taylor Kit R-0006 base demand reagent took 7 drops to bump the sample up to 7.4.

Getting ready to tweak it back to normal.

I might be the worlds shortest user of MPS.

Happy holidays!

 

[chem geek]

Wow. Well it just goes to show you what intentional bather load can do. So sorry about your wife's top. Unlike chlorine that is moderated in its strength by CYA, bromine is not so high bromine levels are, well, actually high even though bromine is a weaker oxidizer than chlorine.

Do you know if your spa has an ozonator?

 

[heykerrdog]

Do you know if your spa has an ozonator?[/QUOTE]

The owner's manual says "optional". I'm pretty sure I don't, but I'll look it over again. Need to pull the panels and chase down a small leak anyways.

Won't that be an "oh sh*!" moment if I find that I do have one