Helping to understand my Nature2 + Dichlor + MPS Sanatizing Routine

[contentedPilgrim]

I developed the below sanitizing routine over the past 16 years with my Marquis 450 gallon spa and it worked well. I am purchasing a new Sundance 980 Lisbon (370 gallon) and am planning to use the same routine (scaled down by 20% for less water) but want to corroborate with others the science behind what I've been doing. Aside from water health, my goal is to have the minimum amount of chlorine in my water.

My routine:

• Nature 2 plus changed every 4 months

• Initial Fill Only: 2 tsp of sodium dichlor (3ppm) - wait an hour then add 1/2 cup of MPS

• Shock weekly with MPS (3/8 cup = 3oz)

• Add 2 tbsp of MPS mid week if heavy use.

• Ozonator

This is my understanding of how it works and what I'd like clarification on:

With the initial water fill, the chlorine binds to contaminants and is turned into chloramines. The weekly MPS shock pulls the contaminants from the chloramines and frees up the chlorine to be active again - but in a minimal amount. The Nature 2 does the rest of the job of sanitizing along with the Ozonator. The new Sundance will also have UV.

As I understand it, this method is difficult to detect the level of chlorine (free or combined), so I'm going by the seat of my pants - and water clarity. I also don't understand what the MPS turns into after added to the water and what accumulates over time because of it.

Other tidbits that probably have something to do with the balance, and I'm including just to make sure I've given all relevant info:

• My water is naturally soft (10 ppm Calcium) and I have to add a fair degree of Calcium at startup.
• My water was frequently basic and I had to add a small amount (1 tbsp) of dry acid to balance.
• Alkalinity was always low. If I tried to get above 60 ppm (using baking soda), the tub would get too basic. I chose keeping the pH balanced and occasionally added baking soda to increase alkalinity to 60 ppm.

Thanks in advance for any insights.

[RDspaguy]

Ozone is not effective as a sanitizer because it does not establish a residual, meaning it only sanitizes what is in the pipe, then returns that to a dirty tub. What it is effective at is oxidizing chloramines and chlorine as well. It's like a shock machine. With 24/7 ozone you will find your FC as well as CC are mostly gone the next day with no chemical odor, irritation, or high chemical residual.

I am a fan of nature2, but not mps. Nature2 is slow acting and not effective against bather-to-bather contamination, hence the need for mps or a sanitizer. I prefer chlorine over mps, especially with 24/7 ozone, but if works for you then keep doing it.

[contentedPilgrim]

Thanks for the reply. I completed my purchase and have spent the last 3 days doing research and read through Chem Geek and Nitro's posts. I've adjusted my initially posted routine as below. I'm still trying to figure out how the ozonator will impact how much MPS I need to add (half?). I am also unsure on borates due to health concerns (banned in the EU).

370 Gallon Sundance Spa with built In ozonator & UV

Nature2 Mineral Stick – changed every 4 months

Initial Fill: This should give me a balanced tub with a Saturation Index of -0.04 (without borates)

• Calcium Hardness - 130 ppm (mine is very low and I have to add calcium)
• pH – 7.6 (stabilized with jets)
• Total Alkalinity - 80 ppm (my well water is low and I add baking soda)
• Borates (undecided) - 50 ppm = 13.5 oz of Boric Acid / 370 gal
• Dichlor – 10 ppm FC (9 ppm CYA) - 1.7 tbsp / 370 gallons
• (Nature2 says 1.5 tbsp / 250 gallons which is 13 ppm FC)

The first week: (to get CYA to between 20-30

• Dichlor - 7 ppm FC (6.3 ppm CYA) – 3.5 tsp / 370 gallons per person hour - 3 doses adds 19 ppm CYA for a total of 28 ppm

Maintenance:

• MPS - 7 ppm CC registered - 2.5 tbsp / 370 gallons per person hour - OR HALF because of ozonator?
• Bleach - (weekly or bi-weekly) – 4 ppm - 2.4 oz / 370 gallons (7.5% bleach)

When Needed

• Bleach - shock – 10 ppm? - 7.7 oz / 370 gallons (7.5% bleach) - w/ added acid first

[RDspaguy]

Overthinker, I see. After use, add enough chlorine to establish 3-5 ppm and walk away. By morning, 0.0 CC, 0.5 FC. If worried about it, add some before use as well.

I have no knowledge of ozone affecting mps since I don't use or recommend mps. Ozone is such a strong oxidizer it destroys other oxidizers, like chlorine. This CAUSES a low chlorine level but many people think, and manufacturers used to advertise, that it REQUIRES a low chlorine level. And in 99.9% of the time it will be fine, but it carries a small risk of contamination. Who wants to be the 1 in a million that gets a flesh-eating bacteria? Statistics don't matter to you then.

[contentedPilgrim]

On 7/10/2022 at 8:51 AM, RDspaguy said:

Overthinker, I see. After use, add enough chlorine to establish 3-5 ppm and walk away. By morning, 0.0 CC, 0.5 FC. If worried about it, add some before use as well.

I have no knowledge of ozone affecting mps since I don't use or recommend mps. Ozone is such a strong oxidizer it destroys other oxidizers, like chlorine. This CAUSES a low chlorine level but many people think, and manufacturers used to advertise, that it REQUIRES a low chlorine level. And in 99.9% of the time it will be fine, but it carries a small risk of contamination. Who wants to be the 1 in a million that gets a flesh-eating bacteria? Statistics don't matter to you then.

Definitely a thinker and certainly don't skimp in my efforts to understand how something works scientifically. From what I can tell, the ozone plus UV should allow me to reduce MPS usage significantly. As far as the 1 in a million for a flesh eating bacteria - way less than that - especially for a private hot-tub. The dangers of chloroform inhalation and absorption (by-products of chlorine usage) are higher on my list of things to avoid. Hence my plan to only use chlorine as a shock once a week and not have residual chlorine in my spa while soaking. The Nature2 + MPS + ozone and UV will take care of sanitation for me.

[RDspaguy]

The point is that ozone gets rid of chlorine, so you can use it to sanitize after you use the spa and have no chloramines, or chloroform, when you use it the next day. Not sure if it will burn off mps as well, but I know alot more people have bad reactions to mps than chlorine, myself included. For these reasons, I recommend chlorine use with 24/7 ozone. 

As it is a private spa, you can do whatever you want. CDC and local health department regulations do not apply to private spas. 

[contentedPilgrim]

6 hours ago, RDspaguy said:

The point is that ozone gets rid of chlorine,

I appreciate your reply. My understanding is that ozone oxidizes chloramines and this creates more FC. Does the FC then off-gas? Or is the chlorine level reduced some other way? If indeed I can work it so that there isn't residual FC, I am open to rethink.  When the ozone oxidizes the chloramines, what are the resulting compounds?

[RDspaguy]

Not a chemist, just a repair man, so I wouldn't know. All I can tell you is ozone eliminates CC, most of FC (all but about .5ppm), and leaves no chemical odor when you open your cover. 

As far as ANYTHING converting CC to FC, I've heard the theory but have never actually seen it happen in a testable manner. CC gets burned off through oxidation as far as I'm concerned. 

Maybe @waterbearcan tell you.

[waterbear]

In a chlorine system you cannot create FC from chloramines. Chloramines are oxidized and either gas off or are converted to salt, which cannot be regenerated into chlorine unless you have a SWCG. (In a bromine system sodium bromide CAN be converted back to bromine sanitizer by an oxidizer such as chlorine, MPS, or ozone.)

If the spa is indoors then the buildup of volatile oxidation byproducts in the air might present a problem much the same as with an indoor pool  but in an outside spa just take off the cover and run it for about 15 min before going in to allow them to gas off.

On 7/10/2022 at 11:51 AM, RDspaguy said:

Overthinker, I see.

Have to agree with @RDspaguy.

[ecstatic]

On 7/7/2022 at 7:39 PM, RDspaguy said:

Ozone is not effective as a sanitizer because it does not establish a residual, meaning it only sanitizes what is in the pipe, then returns that to a dirty tub. What it is effective at is oxidizing chloramines and chlorine as well. It's like a shock machine. With 24/7 ozone you will find your FC as well as CC are mostly gone the next day with no chemical odor, irritation, or high chemical residual.

I am a fan of nature2, but not mps. Nature2 is slow acting and not effective against bather-to-bather contamination, hence the need for mps or a sanitizer. I prefer chlorine over mps, especially with 24/7 ozone, but if works for you then keep doing it.

I'm trying to understand my new ozone/uvc system, do you run ozone and pump round the clock? how about when soaking?

[RDspaguy]

On 11/28/2022 at 2:14 PM, ecstatic said:

I'm trying to understand my new ozone/uvc system, do you run ozone and pump round the clock? how about when soaking?

A system with 24/7 circulation is best, but if your tub does not have a circulation pump and relies on the main pump for flow you do not want to run it continuously. The damage to the pump and your electric bill would outweigh the benefits of running it continuously. 24/7 circulation pumps are fractional hp and made to run non-stop, where your main pumps are much higher hp and can overheat the spa if left on too long.

[ecstatic]

RDspaguy thanks for the response. Yes, I run only one pump a vsp intelliflo. I have been running it on 1250rpm 24/7, roughly 225 watts. Just had to replace motor (5yr old) maybe due to long cycle times. Now have it on 2 6hr cycles. Water quality with uvc/ ozone has been fantastic. Thanks for steering me towards this system.