“MPS is not recognized by the EPA as a sanitizer for recreational water (hot tubs and pools). The only way the EPA recognizes MPS as a sanitizer is if it is used in conjunction with silver ions .”
I did not know this . Our hot tub manufacturer and retailer indicated we could use MPS . This tub did come with something called a Spa Frog that had a silver ion cartridge but we chose not to use it because the cartridge had to be replaced frequently and was not inexpensive. I didn’t think it was required . It is supposed to enable you to use fewer chemicals.
Precisely. The "Frog" system cartridges adds the silver ions (silver nitrate embedded in a slowly dissolving matrix) and the MPS acts mainly as the oxidizer for bather waste. Silver ions are known to be anti-viral and anti-bacterial when in solution and at higher temperatures (104F). The MPS enhances the ability of the silver ions to kill pathogens and somewhat stabilizes the silver ion in solution (silver will readily form insoluble oxides and chlorides when in aqueous solution). The down side to these systems is that there is no way to know what the silver concentration is nor is it easy to figure out how much MPS is in the water, so reliable testing and accurate dosing are out the door and you have to rely on trial and error. Not the best way to manage a body of water.
Yes , most everything you read says bromine is superior for hot tubs . I thought it was more stable , and easier on your skin.
So if we wanted to switch from a bromine spa to a chlorine one, what is the procedure? And what products do you need?
One factor I hadn’t mentioned though, is that this is in a vacation rental and that might make a difference.
I am not sure but I think in a chlorine spa, it is critical to add chlorine every day or after use ? And renters are not going to be good about doing that . We can’t afford to pay someone to come in every day to do it and we are 75 miles away.
The devil is in the details with bromine. The upside of bromine is that, because of it's chemistry in water, sanitizing bromine is almost 99% in the form of hypobromous acid (HOBr) as opposed to hypobromite ion (OBr-). Chlorine, on the other hand, is about 50/50 hypochlorous acid/hypochlorite at a pH of 7.5. So one can make the argument that you have more active sanitizer available with bromine. However, why should that matter? As long as the sanitizing compound is at concentration high enough to kill pathogens at a reasonable rate, it doesn't much matter which one creates more as any excess sanitizer is going to oxidize organics, bathing suits, skin, etc. In fact, some of the oxidation reactions with organic compounds, especially nitrogen containing compounds, are sensitive to the concentration of the oxidizer and, if high enough, you can create more of the nastier smelling stuff. The beauty of chlorine and cyanuric acid is that the CYA acts as a very good buffer for the chlorine concentration and so it greatly reduces the harshness of chlorine in water. The similar analogue of CYA for bromine is DMH but it takes A LOT more DMH to have the same buffering effect on bromine as it does compared to CYA & Chlorine.
As well, both bromine and it's combined nitrogen compound, monobromamine, are effective sanitizers while the corresponding combined chlorine compound, monochloramine, is not an effective sanitizer. However, no one really wants combined bromine compounds around because they tend to smell harsh and irritate mucous membranes. One advantage of chlorine is that you can measure free chlorine separately from combined chlorine and so you can have an easy indicator (the CC concentration) for when it's time to dump the tub. For bromine, the test kit only measured Total Bromine (TB = sanitizing bromine + combined bromines) and so you have no idea if the water contains 100% sanitizing bromine, 100% combined bromine or some fractional split. Thus, aside form a bad smell, you have no good way to know when you should dump the tub.
As for being "easier on the skin" that's totally subjective. There are some people that can't smell bromine compounds nor are sensitive to them and there are others who gag at the smell of bromine and get skin rashes from brominated water. It all depends on the person.
If you can't be there daily or even every few days to manage a tub, then any sanitizer is going to have it's drawbacks. There are salt-water chlorine generators for hot tubs that you can hang over the side of the tub when not in use and it will generate small amounts of chlorine automatically. Some people on the forum here use them and like them a lot. The only downside is that you do have to add salt to your tub water and, if the manufacturer doesn't allow for that, you will void your warranty (if you have any warranty left). Again, I personally think it's a load of baloney to void a warranty for that but the manufacturers don't really listen to reason. Usually when converting a tub to use salt water, one has to have the heater replaced with a higher-end model (typically a titanium heater as opposed to Incoloy or teflon coated steel) to avoid chloride corrosion.
You can stick with bromine in a floater as this is a rental, but I don't think any system is all that reliable in a remote application and, for sure, renters are not going to bother themselves with proper hot tub use and care. There would seem to me to be much more liability on you, the landlord, having a hot tub at a rental that could be potentially dangerous to people (from a health/disease perspective), then to simply shut it down when you are not there and lock the top of it. Then again, a rental with a pool can be equally or more dangerous and so I hope you have good general liability insurance for such matters
