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Do You Need Chlorine If You Use Mps And Silver?


navsav

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Hi all,

I was reading about the nature 2 cartidge and seems that they advertise if you use MPS with this nature cartridge then you don't need any chlorine?

Is this true, and exactly how much MPS do you add on a weekly/daily basis?

What about combination of CL and MPS?

Please let me know what any of you are doing in this regard.

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MPS does not kill bacteria. It only oxidizes some organics. Silver kills bacteria, but does so slowly. Only chlorine is fast-acting at killing bacteria. Technically, the EPA requires use of some sort of fast-acting disinfectant such as chlorine, bromine or Biguanide/Baquacil/PHMB. The use of other secondary disinfectants such as silver is optional.

Chlorine alone is sufficient, but in a hot tub organics can build up so using MPS helps with that and lowers the amount of chlorine demand since the chlorine doesn't need to oxidize as many organics. The main advantage the minerals (silver for bacteria, copper for algae) have is that they are released over time so are always around. With chlorine, you have to add it every day (except for Trichlor pucks). With bromine, you can get a floating feeder so don't need to add it as frequently.

You should look at the MPS dosage on the bottle for pools which I believe is one pound per 10,000 gallons and then scale that down accordingly to the size of your spa or hot tub.

If you use chlorine, then you can also watch the amount of CYA you add since Trichlor and Dichlor both add CYA to the water and it builds up. I'm currently in an E-mail conversation with the bacteriologist who first devised the "Vermont" method which uses Dichlor exclusively since that gets to a point after 1-2 months where the bacteria that causes hot tub itch, Pseudomonas aeruginosa, is no longer killed by the chlorine because the CYA level is so high that it lowers the chlorine effectiveness by too much. I recommend using Dichlor until you get to 20 ppm CYA, which is about when you've added 20 ppm FC so around 1-2 weeks, and then switch to using unscented chlorine bleach. That may be overly conservative, but it will keep your hot tub disinfected properly without being too strong in chlorine (some CYA is good to have, or else the chlorine is TOO strong).

Richard

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Hi Richard,

Do you mind giving me an opinion on a maintenance plan for my tub. This is what I do currently.

I have Ozone and Silver

1) I add 3 OZ leisure time renew (MPS) twice per week

2)I add about 1oz of dichlor (62% available Cl) 2 times per week

I have measure my CYA rencently and it is at 60 PPM according to my taylor kit

(my water is about 3 months old)

Please give me your suggestion as to what change I should make to my current procedure. Do you see anything completely wrong with my setup?

Thanks for your help

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Hi all,

I was reading about the nature 2 cartidge and seems that they advertise if you use MPS with this nature cartridge then you don't need any chlorine?

Is this true, and exactly how much MPS do you add on a weekly/daily basis?

What about combination of CL and MPS?

Please let me know what any of you are doing in this regard.

If I used any silver cartridge with MPS, my water would cloud up. Same thing if I used silver with MPS and shock with chlorine weekly. I found the best way to keep my water was to add chlorine after each use. The silver cartidge will allow you to use a little less chlorine and will help in between uses.

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The only issue is that chlorine usually dissipates quickly, especially when you use the hot tub. Also, ozone tends to oxidize chlorine turning it into chorates (via chlorites). So first thing I would do is test the water for chlorine before you get into the spa and see if it's low or zero due to only adding Dichlor twice a week. If it is, then you should be adding chlorine more frequently, though the silver is a safety net for that. Second, with the CYA higher, you can use unscented bleach instead of Dichlor as your source of chlorine. I am a bit surprised at how low your CYA is given that the water is 3 months old. It implies that you've cumulatively added about 0.75 ppm FC per day on average or around 2.6 ppm twice a week. That's not very much. On the other hand, 1 ounce of Dichlor in 500 gallons should add 8.3 ppm FC and 7.6 ppm CYA. So either the CYA isn't building up as fast for some reason or my 500 gallon assumption for the hot tub is wrong. Chlorine may slowly breakdown CYA and maybe the higher temps accelerate that, but this would be new info.

In any event, the CYA issue is only a problem for hot tub itch and that's somewhat rare so it's really up to you. The ozonator will kill the bacteria that causes hot tub itch so long as it is free-floating and gets circulated. Bacteria that is stuck in bio-films on surfaces will only get killed by the residual disinfectants -- fact-acting chlorine and slow-acting silver.

You probably only need to use the MPS once per week unless you use the tub frequently -- every day.

There is nothing "completely wrong" with your setup. If you wanted to save money, you could just use chlorine alone and not have the Nature 2 minerals nor the ozonator. Chlorine alone will kill the bacteria, but it's a bit of a pain since it doesn't last long. Bromine is more convenient in that regard with its slow-dissolving feeder, but some people are allergic to bromine or don't like it's "different" smell. You can certainly keep what you have and just supplement with bleach instead of Dichlor and be fine.

Richard

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Thanks Richard,

you made a correct assumption on the CYA level - I acutally didn't start adding much chlorine until recently so for the first two months chlorine was added only in minimal quantities. So thats why the number I quoted sounds low to you.

I would like to save some money - the nature 2 cartidge is 30 bucks so for a 4 month cartridge thats not very expensive. The shock on the other hand does get expensive over the long run when using it twice per week. I purchased a bulk supply of di-chlor off of some guy on craigs list so have at least a two year supply!! So maybe I should use more chlorine and less MPS?

My hot tub is used sloely by me and very rarely maybe once per month do I have a guest in it. I do however go in the tub at least 5-6 times a week for 30-45 minutes at a time. Do you think at this frequency I could add MPS just once per week?

using bleach sounds scary - how much do you add and at what frequency? Is it the same bleach you use for clothes?

Also at what ppm of cya does it begin to slow down the chlorine effectiveness?

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I'm glad my calculations were about right and it was just that you didn't use as much chlorine earlier. Last thing I need is one more mystery to figure out! :wacko:

You certainly don't need the Nature 2 system. And the shock can be done just once per week. The non-chlorine shock, MPS, is only to help oxidize organics so that chlorine doesn't have as much to do and to break down some organics that chlorine has a harder time handling. Another option for that is to use an enzyme, but that only helps speed up the breakdown of organics by chlorine -- so an enzyme won't cut down the amount of chlorine needed whereas MPS does (somewhat). So I definitely think you can just add the MPS once per week at the dose on the bottle (1 pound per 10,000 gallons for a pool) scaled down appropriately for a spa (so 0.8 ounces weight per 500 gallons?).

The Dichlor you are using produces EXACTLY the same chlorine in the water as bleach does. So it's nothing to be scared about. The only difference is that with bleach you won't be increasing the Cyanuric Acid (CYA) level. And yes, this is the same bleach as used for the laundry, but make sure it is unscented and either Clorox Regular (which says "6% Sodium Hypochlorite" as well as "5.7% Available Chlorine" because it is registered as a disinfectant for use in pools) or an off-brand Ultra product (which is a bit riskier since they are not always 6%).

CYA slows down chlorine with even very small amounts in the water. Technically, the CYA combines with chlorine to form new compounds called chlorinated cyanurates that are not effective disinfectants nor oxidizers. It's a ratio thing, but even at 1:1 CYA to FC the chlorine effectiveness is cut in half. When the ratio of CYA to FC is more than about 5 to 1, then the chlorine effectiveness (at a pH of 7.5) is reduced by a factor roughly equal to the CYA amount in ppm. So 4 ppm FC with 20 ppm CYA the chlorine effectiveness is cut down by a factor of 17 (so approximately 20) and has the same amount of disinfecting chlorine (hypochlorous acid) as 0.23 ppm FC with no CYA. 4 ppm FC with 40 ppm CYA has chlorine effectiveness cut down by a factor of 39 (about 40), etc.

You want some CYA in the water or else the chlorine will be TOO strong -- so some CYA is good, but too much isn't. The risk is small, however, since most bacteria are VERY easy to kill. It's really only hot tub itch that you have to worry about and most people don't get that. So don't stress out over this. Besides, you said you had an ozonator so that will kill hot tub itch as long as it is free-floating so makes it's way through the ozonator.

Since you've made an investment in Dichlor, you could just continue to use that and hope your ozonator handles hot tub itch or that you are not susceptible to it. That's a reasonable thing to do. Or you can use Dichlor for a short time, 1-2 weeks, certainly not more than 1 month, and then switch to bleach after that. In a 500 gallon hot tub, it takes a little under 1/2 ounce weight of Dichlor to raise the FC by 4 ppm. It takes a little more than 4 fluid ounces of 6% bleach to do the same thing. Regardless of which you use, I suggest you add it about a half hour before you use the tub and also take the cover off which will reduce any vapors or smell. This will ensure anything that grew in the tub pretty much gets killed before you use it, even if the chlorine went to 0 and the ozonator wasn't on. If you don't plan on using the tub the next day, then add another dose of chlorine after you get out; otherwise just repeat the procedure the next day.

Richard

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