dipotassium peroxodisulphate vs potassium peroxymonosulfate (MPS)


Well-known member
Oct 4, 2018
I'm wondering if someone here can help me with something. I believe I read somewhere on another forum that Beachcomber's Care-Free product is MPS but if you look at the MSDS sheet for it here, it's actually comprised of:

Dipotassium Peroxodisulphate 30 - 60% by weight
Sodium Sulphate (Glauber's salt) 10 - 30% by weight
Sodium hydrogen sulphate (Anhydrous Glauber's salt?) 10 - 30% by weight

I'm guessing that dipotassium peroxodisulphate and MPS are farly similar chemicals but what are the differences between them in terms of how they act or in the water or their effectiveness? Does one have advantages over the other? Does dipotassium peroxodisulphate just break down/dissociate into MPS in the water?

What function/purpose, if any, would the Glauber's salt and Anhydrous Glauber's salt have in the product?

I have used Beachcomber's Care-Free system in the past and like how the water doesn't have a chlorine odor to speak of but Care-Free is a REALLY expensive product. I'm planning to use the Bleach/Dichlor system supplemented by either Care-Free or MPS with the next tub I'm getting soon (1995 Hot Springs Grandee). I can get generic/department store brand MPS for about 1/6th the cost of Care-Free. Am I going to notice anything much different by switching to plain old MPS from Care-Free other than the extra cash in my wallet? ;)


TFP Expert
Mar 2, 2011
Potassium persulfate (potassium peroxydisulfate) can cause an allergic reaction in a significant number of people.

I would recommend avoiding it. Monopersulfate is less likely to cause an adverse reaction. But, I don't think that it's very useful, either.


Well-known member
Oct 4, 2018
I used Care-Free for several years and never had a reaction to it and neither did anyone else who used the tub. Likewise, friends of mine have used it for years in their tub and have had lots of guests use it and no one has had any sort of allergic reaction to it. I'm surprised to hear it said that dipotassium peroxodisulphate causes allergic reactions in significant numbers of people given that Beachcomber sells a lot of that product to a lot of people. I'm not sure what the explanation could be but that's not what I posted to find out about.

The allergy issue and opinions on the usefulness of MPS aside, my original questions still stand. Thanks.

EDIT: I've found the answers to a couple of my questions. Sodium Hydrogen Sulphate is Sodium Bisulfate which, of course, is used to lower alkalinity and pH. The Glauber's salt, sodium sulphate, is an impurity that comes with the sodium bisulfate. Most pH down products are something like 90 sodium bisulfate and 10% sodium sulphate so my guess the actual ratio of sodium bisulfate to sulfate in the Care-Free is also about 9:1. So that just leaves the questions about the dipotassium peroxodisulphate and MPS to discuss... Can anybody help out on this?


Silver Supporter
Bronze Supporter
TFP Guide
Oct 20, 2017
Southern WI
Pool Size
Liquid Chlorine
I have used Beachcomber's Care-Free system in the past and like how the water doesn't have a chlorine odor to speak of but Care-Free is a REALLY expensive product.
Chlorine odor is from CCs, not chlorine. A properly managed chlorine pool or spa should not have a strong chlorine odor. Don't believe me? How much chlorine smell does a bottle of bleach have? Next to nothing.

Though I don't know anything about DPS, I'd say there's no reason to use it over MPS. Please do note that MPS cannot replace chlorine, and can't break down CCs. It's only useful to oxidize waste before it can turn into CCs. It will also falsely show up as CCs on the FAS-DPD test, so you'll have to purchase an extra Taylor reagent to get a valid test.

I also wouldn't like that it adds sodium bisulfate. With TFP you'll get your pH Rock solid, and adding that will only screw up the Rock solid pH you'll have.

Oh, and like James noted, you don't need MPS either. It's optional. It may provide some benefits in some situations but it's 100% not needed. That will keep the most cash in your wallet. ;)