difference between mps/monopersulfate and sodium thiosulfate use in hot tub, spa

[Blakew81]

Hello, When we got our spa we bought some sodium thiosulfate that came in handy whenever we accidentally added too much chlorine. The cover on the spa (275 gal.) is on except when in use in evenings and when adding chemicals and sits in the shade all the time. It definitely did the trick and of course learned early on not to add too much or all the chlorine was neutralized.

I spoke with the manufacturer this week about another issue and the rep randomly mentioned using MPS to 'shock' it periodically before adding more chlorine back in. I knew I didn't want to get too high CYA levels so I only used dichlor until the cya levels were good and then stayed with liquid chlorine throughout the week. So ...

Any reason to buy and use MPS instead of the thiosulfate we've been using (rarely now)?
Any reason to use a lot as a 'shock' weekly or biweekly and then start again?
With either option will shocking it remove CYA? She seemed to suggest using dichlor regularly but that continually raises cya is my understanding.

Thanks!

 

[ajw22]

Welcome to TFP.

MPS and sodium thiosulfate are different chemicals that do different things.

Any reason to buy and use MPS instead of the thiosulfate we've been using (rarely now)?

Thiosulfate neutralizes chlorine. Read Free Chlorine - Further Reading

MPS is an oxidizing agent that breaks down organic materials without increasing chlorine.

Any reason to use a lot as a 'shock' weekly or biweekly and then start again?

MPS breaks down chloramines, which are byproducts of chlorine sanitation. Chloramines are what give a pool/spa the chlorine smell.

Chloramines can also be burned off by UV. If the spa is covered and does not have a UV system MPS can be used to eliminate the CCs that accumulate in the water.

CC - Further Reading

www.troublefreepool.com

With either option will shocking it remove CYA?

No.

CYA is only removed by draining and exchanging with fresh water.

CYA - Further Reading

www.troublefreepool.com

 

[phonedave]

1) When you say you have too much chlorine, how much are your talking about? The safe bather range for FC is quite large (it depending on CYA) and in a hot tub, FC is pretty easy to lower without chemicals. Unless something crazy happens, like you spill your bleach bottle into the hot tub, there really is no need to keep thiosulfate on hand.

2) As was said MPS is an oxidizer, it helps to get rid of CC. However chlorine is also an Oxidizer, and you are going to be adding that anyway. Also, some people are allergic to MPS (they get a rash). So given the MPS may have a down side, and that plain old bleach does the same thing, there is no need to keep MPS on hand either.

There is no reason to shock/slam your hot tub on a schedule. As long as you keep FC where it needs to be, it will be fine. If things get out of hand, then by all means it may be necessary to shock it (or just change the water)

 

[Bperry]

Hello, When we got our spa we bought some sodium thiosulfate that came in handy whenever we accidentally added too much chlorine. The cover on the spa (275 gal.) is on except when in use in evenings and when adding chemicals and sits in the shade all the time. It definitely did the trick and of course learned early on not to add too much or all the chlorine was neutralized.

I spoke with the manufacturer this week about another issue and the rep randomly mentioned using MPS to 'shock' it periodically before adding more chlorine back in. I knew I didn't want to get too high CYA levels so I only used dichlor until the cya levels were good and then stayed with liquid chlorine throughout the week. So ...

Any reason to buy and use MPS instead of the thiosulfate we've been using (rarely now)?
Any reason to use a lot as a 'shock' weekly or biweekly and then start again?
With either option will shocking it remove CYA? She seemed to suggest using dichlor regularly but that continually raises cya is my understanding.

Thanks!

Lots of people think their chorine is too high when it actually isn’t. How are you testing the water?

 

[Blakew81]

Lots of people think their chorine is too high when it actually isn’t. How are you testing the water?

through test strips: Amazon.com

When you say you have too much chlorine, how much are your talking about?

Honestly when cc/tc or fc get in the dark colored areas. using strips shared above. already bought the thiosulfate back when we get it and used it to reduce from the dark purple FC area.

there is no need to keep MPS on hand either.

we plan on using bleach once the pool chlorine bottle is gone. will just have to calculate/test different amounts as the one we had seem rather diluted given how much we end up having to use to get it in the right colors/amounts

There is no reason to shock/slam your hot tub on a schedule. As long as you keep FC where it needs to be, it will be fine. If things get out of hand, then by all means it may be necessary to shock it (or just change the water)

Do you mean add a little chlorine (or bleach in future) daily even if it's in shade and unused throughout the week to keep FC up? or just test periodically and add when needed?

MPS breaks down chloramines, which are byproducts of chlorine sanitation. Chloramines are what give a pool/spa the chlorine smell.

Chloramines can also be burned off by UV. If the spa is covered and does not have a UV system MPS can be used to eliminate the CCs that accumulate in the water.

Thiosulfate neutralizes chlorine. Read Free Chlorine - Further Reading

MPS is an oxidizing agent that breaks down organic materials without increasing chlorine.

Thanks @ajw22 - I guess I'm a little confused by the language reading that article. sodium thiosulfate 'neutralizes chlorine', vitamin C 'removes' chlorine' and hydrogen peroxide 'breaks down' chlorine.

What I want to do is to not let CYA get too high that I have to drain the water too often which is why I didn't want to use dichlor over and over but eventually transition to pool chlorine or even better now, liquid no-addins bleach. But that would be a regular add in. Now I'm learning about regularly 'shocking' the system. but if the levels are fine, why shock it? And which levels? CC/TC? FC, something else?

 

[ajw22]

Thanks @ajw22 - I guess I'm a little confused by the language reading that article. sodium thiosulfate 'neutralizes chlorine', vitamin C 'removes' chlorine' and hydrogen peroxide 'breaks down' chlorine.

Theosulfate is like dropping a nuke on the chlorine. Hydrogen Peroxide is like hitting it with a cruise missile. Vitamin C is dropping a grenade on it. They all consumer chlorine, some much more than others.

What I want to do is to not let CYA get too high that I have to drain the water too often which is why I didn't want to use dichlor over and over but eventually transition to pool chlorine or even better now, liquid no-addins bleach.

Removing chlorine has nothing to do with CYA levels. Removing chlorine will not affect CYA.

Don't use chlorine products that contain CYA.

Now I'm learning about regularly 'shocking' the system. but if the levels are fine, why shock it? And which levels? CC/TC? FC, something else?

Shocking pools is not part of TFP methods. We do not recommend shocking pools.

Depending on your spa use it may need shocking to eliminate CCs. If you have small bather loads in your spa and change water often then shocking is not needed.

 

[Bperry]

through test strips: Amazon.com

If you want to follow TFP, you’ll need to get a more reliable test kit. Those paper strips are pretty unreliable and you’re likely to goof things up trusting them. Look through many of the threads on the forum to see what I mean.

 

[A.O.]

Go read this ( How do I use Chlorine in my Spa (or pool)? ) it will make things so easy for you!

 

[Mdragger88]

Go read this ( How do I use Chlorine in my Spa (or pool)? ) it will make things so easy for you!

This
Along with
Pool Care Basics
& understand that dichlor increases cya by approximately 1ppm for every 1ppm of fc it adds.
To keep the tub sanitary you must keep fc (free chlorine) above minimum for your cya at all times or nasties will grow


As mentioned- the strips are about useless, they have wide ranges, can bleach out, are quite subjective & in general aren’t very accurate.
You need an accurate drop based test kit to properly manage your water
See—> Test Kits Compared


Also, just so you’re understanding:
Fc is free chlorine (good stuff/free to sanitize) - you want this to be in target range as listed on the chart
Cc is combined chlorine (bad stuff/spent chlorine) - you ideally want this to be 0.5ppm or less
TC is Total Chlorine Fc+cc= TC
You need to know what your fc & cc are separately so you know how much good stuff or bad stuff you have.
The TC number alone is not helpful nor is it an indicator of sanitary water.

 

[phonedave]

through test strips: Amazon.com


Honestly when cc/tc or fc get in the dark colored areas. using strips shared above. already bought the thiosulfate back when we get it and used it to reduce from the dark purple FC area.

we plan on using bleach once the pool chlorine bottle is gone. will just have to calculate/test different amounts as the one we had seem rather diluted given how much we end up having to use to get it in the right colors/amounts


Do you mean add a little chlorine (or bleach in future) daily even if it's in shade and unused throughout the week to keep FC up? or just test periodically and add when needed?





Thanks @ajw22 - I guess I'm a little confused by the language reading that article. sodium thiosulfate 'neutralizes chlorine', vitamin C 'removes' chlorine' and hydrogen peroxide 'breaks down' chlorine.

What I want to do is to not let CYA get too high that I have to drain the water too often which is why I didn't want to use dichlor over and over but eventually transition to pool chlorine or even better now, liquid no-addins bleach. But that would be a regular add in. Now I'm learning about regularly 'shocking' the system. but if the levels are fine, why shock it? And which levels? CC/TC? FC, something else?

1. Test strips are horrendously inaccurate and unrealizable. At the least, for a hot tub, you should have a a FAS/DPD drop based kit for Free Chlorine and Combined Chlorine (and by extension - total chlorine) as well as drops for Total Alkalinity and pH. To round out the mix, it would be good to have Calcium Hardness as well as CYA tests too. All drop based, no strips

2. "Dark colored area" means nothing. Numbers are what counts, parts per million. The amount of chlorine you should have is dependent on your CYA level, not some arbitrary color on a strip

3. Just a though, are you using the Frog system in your tub? The Frog system totally screws up tests, if you are using it.

4. You will get to know your tub over time. All are slightly different. With my particular tub, I know that if I get my free chlorine around 4.0 to 5.0, I can go two (maybe three) days without adding chlorine if there is no use. I have been using this tub long enough that once I have it dialed in, I can go 4-5 days without testing. I just "know" what it needs. 2 oz after my wife and I use it, and 1.5 to 2 oz every few days. However I test roughly 2x a week, just to be sure of where I am at. I also test if there are any sort of anomalies such as having a party, or my kids using the tub, or anything that is outside of the routine I am used to.
For you, you should be testing frequently (daily even) to get used to how your tub behaves. Once you know that, then you can go a few days between testing.

You don't list the specifics of your tub in your signature (please do), but having ozone makes a difference as well as your filter schedule.

Ozone removes chlorine. Ozone generators only run during filter cycles (usually). So if you have ozone, and depending on how much you filter, your tub will loose chlorine.