Aquarium guy wondering about mystery spa that never gets treated...

[davemill]

I'm a long time aquarist, kept large planted aquariums with added CO2 and macronutrients, etc. Not relevant here except I'm accustomed to measuring and adjusting water chemistry. Everything I know about spas I learned from this forum during the last few weeks.

So a couple of years ago I moved into my new wife's home with a 1997-vintage Hot Springs Prodigy spa. She told me her maintenance routine was to throw in some chlorine, and to clean the filters and run the cleaning cycle "when it needed it." She also changed the water 1-2 times per year. The spa remained on her chore list.

About that time we replaced the ancient spa cover with one of the bi-fold, solid covers. Works great, and as an aquarist I noticed that it created a positive pressure, wet, airtight seal over the spa. If you do that on an aquarium into which you are diffusing CO2, all your fish will die overnight because the CO2 displaces the all the Oxygen above the surface of the water. No Oxygen available to diffuse into the water, fish die. The solution is to allow air to circulate above the water. I'm speaking from experience on that one.

In February 2017 ago the spa quit working. I replaced the circulation pump (it is supposed to run 24/7 but had frozen). The ozone generator was a dozen years old, so I replaced that with a new CD ozone generator. I replaced the filter on the circ pump and bleached and cleaned the other two that were in great condition. Spa "worked" again, and we briefly smelled ozone every time we flipped open the cover. I figured that the ozone was filling the airspace over the water because of the positive-pressure seal from the new cover. I changed the water and lightly cleaned the spa (scrub sponge and salt, the way you clean an aquarium). It did not appear to need any further cleaning.

Recently my wife told me that she had quit adding any chlorine to the spa since I replaced the ozone generator, because it no longer "needed it." She has not even run the cleaning cycle. The only maintenance in a whole year has been cleaning the filter. Water is crystal clear, and has no odor or slimy feel or algae or surface film or color tint or condensed granules or any of the other symptoms I read about in this forum. (I know that none of those observations are actual data.) Our water is quite hard here, but because there's no evaporation, there's no calcium deposits around the edges.

I came to this forum to see if I could figure out what's going on. In one of the many valuable threads here, I discovered this paper:
https://www.absoluteozone.com/assets/ozone_for_municipal_spa_and_pool_treatment.pdf

I'm reading it for the third time now, it's full of great data. Among the most interesting statements are:

FACT #3: Application of ozone generated in proper concentrations, by corona discharge, in proper dosages, and with sufficient reaction times, will provide adequate disinfection as well as chemical oxidation.
FALLACY #3 Ozone will oxidize all pool and spa organic materials totally to carbon dioxide and water.
FALLACY #4: Ozone alone can remove all contaminants from pool and spa waters.
​

Adding all this together, here's what I think is happening in our spa:

• With the cover on 23 hours per day, the CD-generated Ozone concentration is sufficient to "provide adequate disinfection as well as chemical oxidation." (Fact #3)
• The ozone is NOT completely oxidizing all contaminants, nor removing all contaminants. (Fallacies #3 & 4)

So (finally) my question: While I usually follow the credo, "Don't fix what ain't broke," I can't help but wonder what's still dissolved in our spa water, and what steps to take. Having done some research, I feel like we should be following the chlorine or bromine disinfection routines in the stickies on this forum. But the water is crystal clear!!

All opinions welcome!

 

[JoyfulNoise]

Do you know what size your ozone system is or how much ozone it generates (usually listed as mg/day or some such unit).

Ozone is both an oxidizer and a sanitizer. The way you are using it is like the way water treatment plants use it - contact tank method. Your spa water is essentially having ozone bubbles through it continuously and the spa is staying tightly closed so there is a residual ozone level in the water and in the air space above it. In that scenario, ozone can work.

Problem is, what happens when the ozone generator fails without warning (they do that all the time)? Now you’ll have a completely unsanitized body of water that is ripe for bacterial growth. As an aquarist you know full well that a spa sits right in the “Goldilocks Zone” for biological growth. So, without a residual sanitizer in the water your spa will turn into a 350 gallon used bathtub in no time.

If you are going to use the ozone system, then I would suggest you use bromine in the tub as ozone will oxidize bromide into sanitizing bromine and that residual will last a lot longer than ozone.

- - - Updated - - -

Oh, and I also suggest you use Ahh-some next time you exchange the water - there may be a good deal if biofilms in the pipes that needs to be cleaned out.

 

[davemill]

Do you know what size your ozone system is or how much ozone it generates (usually listed as mg/day or some such unit).

DelOzone Spa Eclipse Corona Discharge, 50-70 mg/hr, about $92 now on Amazon
https://www.delozone.com

If you are going to use the ozone system, then I would suggest you use bromine in the tub as ozone will oxidize bromide into sanitizing bromine and that residual will last a lot longer than ozone.

Oh, and I also suggest you use Ahh-some next time you exchange the water - there may be a good deal if biofilms in the pipes that needs to be cleaned out.

@JoyfulNoise, Thank you for your advice!

 

[Arobbert]

The main problem I see with an ozone only system is that there is no way to test for adequate ozone levels. It sounds like davemill got really lucky. Most users I read about (myself included) have not had that experience with ozone. There is a very cumbersome test for unit functionality but it looks like a one shot deal that is expensive and labor intensive. You won't know there is a problem until your water goes south. It would be nice if there was a unit that would self detect failure and an easy way to detect levels in the water.

 

[JoyfulNoise]

The main problem I see with an ozone only system is that there is no way to test for adequate ozone levels. It sounds like davemill got really lucky. Most users I read about (myself included) have not had that experience with ozone. There is a very cumbersome test for unit functionality but it looks like a one shot deal that is expensive and labor intensive. You won't know there is a problem until your water goes south. It would be nice if there was a unit that would self detect failure and an easy way to detect levels in the water.

I completely agree. The primary goal of TFP is teach people how to care for their recreational water toys by educating them on what chemicals do and to only add the exact chemicals to the water that are needed. This requires testing, dosing and then retesting.

Ozone is one of those things that looks great on paper (strong oxidizer, powerful disinfectant, simple method of generating) but in practice has huge downsides (no residual, no direct testing method, fragile equipment that fails without warning). This is one reason why the EPA does not allow it to be used as a primary sanitation system - it’s too easy for it to fail and leave the water in a dangerous state.

One could try to measure total oxidizer levels in the water by first adding the R-0003 iodide drops to see if the ozone oxidizes it to triiodide which would then be reactive to the DPD indicator. [EDIT] I was wrong about the sequence and the chemistry - one would add the DPD powder first and then the iodide. At that point, any residual O3 would oxidize the iodide into iodine/hypoiodous acid which would then react with the DPD indicator. Thanks to JamesW for clarifying that.[END-EDIT] However, I doubt much would be detected as that particular ozone unit only puts out about 40ppb/hr ozone in a 350gal tub which is a fairly small amount of O3.

Again, it’s best to run a tub with a residual sanitizer and bromine isn’t a bad choice when ozone is available.

 

[davemill]

It sounds like davemill got really lucky. Most users I read about (myself included) have not had that experience with ozone. There is a very cumbersome test for unit functionality but it looks like a one shot deal that is expensive and labor intensive. You won't know there is a problem until your water goes south. It would be nice if there was a unit that would self detect failure and an easy way to detect levels in the water.

Yes, it's certainly a lucky circumstance that the airtight seal, plus the continuously generated positive pressure of Ozone, is displacing the oxygen. There is also some regular qualitative testing going on:

1. Test 1: We can smell the ozone. Ozone is present. No further test necessary.
2. Test 2: The water is crystal clear (I took water from the spa in a clear jar and held it up to the sun). Ozone is having the desired effect.
3. We know from the paper quoted previously that the Ozone is NOT removing all contaminants. New mitigation: Quarterly 100% water changes.
4. We know from the paper quoted previously that the Ozone is NOT oxidizing the contaminants completely. New mitigation: Bromine dosing.
5. We know that ozone generators will fail with no warning. New mitigation: buy replacement ozone generator for when (not if) current generator fails.

Am I being naive, or will this new "Water changes + bromine + backup ozone" regimen work without further testing being necessary?

Thank you.

 

[JoyfulNoise]

Testing is absolutely key to everything that is taught here. If you say that “I have a hot tub but I don’t test it regularly because I’ve got all these layers of safety going for me...” then most folks here are going to laugh at that and call you crazy. Without testing, you simply have no idea what’s in your water.

Simple question - when you ran reef and fish tanks, did you ever think you could do a good job and get away without testing the water? Come on, you know that testing is key.

Also, a good quality test kit will set you back what, maybe $100 if you go with all the bells and whistles?? That’s a small investment to make in your own personal health and safety.

Read the forum sticky on running a bromine tub (with testing) - How do I use Bromine in my spa (or pool)?

It’s really not all that hard...you can even establish the bromide bank using sodium bromide and then run your tub as usual and see how good your ozonator is at bringing up the sanitizing bromine levels (total bromine). If your tub is truly as clean as you think it is, then the bromine will come up right away. If there are contaminants in the water or plumbing, then even using chlorine to activate the bromine will not work to create a measurable sanitizer level.

 

[davemill]

Matt,

Please understand that I'm really grateful for you engaging with me on this. I've read dozens of your posts and learned from them all!

Without testing, you simply have no idea what’s in your water.

You are correct.

Simple question - when you ran reef and fish tanks, did you ever think you could do a good job and get away without testing the water? Come on, you know that testing is key.

It's funny you should ask that. About 15 years ago, Tom Barr, an experienced aquarist who later earned a late-career PhD in aquaculture, proposed a testing-free way to succeed with planted freshwater tanks. The technique is called the Estimative Index (EI), you can read about it here:

https://barrreport.com/articles/the-estimative-index-of-dosing-or-no-need-for-test-kits.38/

Prior to EI, we tested pH, KH, Nitrate constantly. With EI, I tossed my test kits. It's completely off-topic here, but fascinating if you are interested.

Read the forum sticky on running a bromine tub (with testing) - How do I use Bromine in my spa (or pool)?

It was one of the first things I read here.

It’s really not all that hard...you can even establish the bromide bank using sodium bromide and then run your tub as usual and see how good your ozonator is at bringing up the sanitizing bromine levels (total bromine). If your tub is truly as clean as you think it is, then the bromine will come up right away. If there are contaminants in the water or plumbing, then even using chlorine to activate the bromine will not work to create a measurable sanitizer level.

Challenge accepted. I'll report back on this thread with quantitative test results.

 

[cfherrman]

You cannot see pathogens in your water, clear water does not mean safe water

 

[davemill]

You cannot see pathogens in your water, clear water does not mean safe water

Thank you for pointing out my error. Clear water means only that nothing is tinting the water brown, yellow or green or creating a film, to the limits of my vision. It's another coarse qualitative indicator like sniffing ozone. Thank you.

 

[Arobbert]

Would a CC test provide an indication of a problem? Or wouldn't that work because there is no chlorine or bromine?

I've noticed that my water gets cloudy the second there is a problem.