Welcome to our forum.
Heat is a big enemy of ozone half-life ...In my HotSpring Grandee (2001), the ozone is "injected" on the heater line - meaning that, if the heater is on, the ozone is being injected into water that is about 120'F - not good at all for efficient introduction of ozone.
can we accurately determine the "pay back" period based on any accurate data?
I know this is very frustrating to folks who like to have a demonstrable ozone level, because you simply won't get one.Didn't you test your water once? I know that you talked about testing your spa water for dissolved or aqueous phase ozone, and I know you have the lab and equipment to do so, and if I recall correctly you either got NO reading, or your equipment wouldn't go that low or something like that. Refresh my memeory please?Chas,Yes, it is frustrating. Do I take it (from your comment) that this means that the industry is still unable to document a sustained ozone residual in a hot tub? Regarding my testing, you are correct - actually, there were two facets to my tesing. Keep in mind, that the information I'll be giving here is for my own tub; and may not be representative for the "universe" of tubs.1) Ozone residual: I modified my ozonator loop (contact chamber) to give a sample port immediately downstream of the Mazzei injector. I also rigged a sampling device to sample water coming out of the end of the contact chamber. I turned off the heater so that the water temp being injected into was my normal tub temp at the time (about 102'F). Using an accurate digital colorimeter and indigo trisfulfonate (a test specific for "dissolved" ozone - the form of ozone you want), I collected a "blank" sample to zero the colorimeter as well as replicate samples from each of the sample points. No ozone was detected at either point - my particular detection level was 0.03 ppm, so, if any dissolved ozone was present, it would be below that level. I also collectd random samples from various points in the tub - as you would expect, no dissolved ozone in any sample.2) Ozone and Nature 2 only - another test involved my operating my tub for a brief period of time without use of dichlor. The tub was "seeded" by normal use - but then, instead of adding dichlor, I left the tub with only the HS ozone (24/7) and the Nature2 (silver ions - principally). Within 48 - 72 hours, heterotrophic plate count bacteria levels went from my normal "0" or single count per mL to, as I recall (I can check rhtubs.com archived posts and find this) to counts of more than 1,000,000 per mL. There are approximately 5 mLs per teaspoon and nearly 2,000,000 mLs in a 500 gallon hot tub. So, if each mL had 1,000,000 bacteria in it, then you are taling of approximately 2 x 10 to the 12th power. That's a lot of bugs. The water was cloudy (although that isn't a good measure by itself). I added a shock dose of chlorine (dichlor), took samples after one hour (or so) and levels were back down to detection levels.Keep in mind, that heterotrophic plate count bacteria may not contain a single pathogenic bacteria - or it may contain a lot. It is simply a very general grouping of bacteria that is used by some organizations (such as WHO) as a rough measure of microbiologicaly quality of drinking water. Regardless of whether pathogens were involved or not, however, who (not I) wants to sit in water in which you have to wonder whether the bacteria you know to be present are harmful or not.Perhaps subject of another post - use of ions and ozone as a secondary sanitizer, or perhaps as a bacteriostatic vs. bactericidal treatment...Vermonter
I don't think an ozone system would ever pay itself back. First: you most likely will substitute MPS for daily use, which costs more than Dichlor. Second: you will most likely add a Nature2 cartridge, which is an additional cost. Third: some ozone units require a 'chip' replacement about every year - that is extra money.
Understanding it's not 100% needed nor is there a direct payback in value, Steve