How important is FC levels in a Jacuzzi with ozonator?

[Fungi]

Hi folks!

Yes, while I add chlorine before use, it's been to zero over and over yet there has been no observed problems. Lucky or science?

Why are there so few post in the hot tub section?

Thanks!

 

[Azgirl71]

I honestly don't know, Jim. I would guess it is just as important as it is in a pool. It may have just been dumb luck nothing has happened.

 

[Fungi]

haha Hi Lisa, well you are all over the place here. The ozonator is a very powerful sanitizer in itself. Just wondering if there are others who have had the same experience as I have.

 

[Azgirl71]

Hopefully someone else will chime in soon.

 

[chem geek]

It depends on how powerful the ozonator and especially how long it runs. If it's on nearly all the time then it may be leaving some residual ozone in the bulk water and that would disinfect it, but generally most spas do not run the ozonator all the time or specifically when the spa appears to be in use (jets on, for example), because ozone will outgas and is an EPA-regulated air pollutant that can damage the lungs. It also will wear on hot tub covers more so than chlorine.

We've definitely seen spas with ozonators go south so they aren't a guarantee. Unless the ozonator was on nearly all the time and putting out excess ozone getting into the tub, then it wouldn't do anything to pathogens growing on spa surfaces that since they don't get circulated. The half-life of ozone is on the order of 15-30 minutes so it won't last very long after it is turned off.

Also, normally one adds chlorine AFTER one uses the spa and does so in sufficient amount so that there is a measurable residual the next time one uses the spa (or the next time one doses if one doses in between soaks). The good news with an ozonator is that the ozone can oxidize bather waste so that it takes less chlorine to do so after a soak. The bad news is that ozone reacts with chlorine increasing chlorine demand so if you don't use the spa every day or two then you end up needing to use more chlorine in between soaks and to add it more frequently. Roughly speaking, an ozonator cuts down the amount of chlorine needed after a soak by roughly half, but it also roughly doubles the rate of chlorine loss in between soaks. In your case, the numbers may be even higher if the ozonator is on all the time.

A more ideal situation would be to have the spa disinfected by low amounts of chlorine and then to have the ozonator come on right after a soak to help oxidize bather waste and to have chlorine dosed just subsequent to that and in between soaks but have the ozonator turned off at that point. Unfortunately, spa ozonators don't work that way.

 

[Fungi]

Hi CG, I appreciate the feedback.

Ozonator runs 24-7 on the smaller filter pump. I know if it's working when I open it and smell those wonderful green apples. lol And yep the inside of the cover is pretty distressed.

I put in a little over 2 oz. of bleach before use, and a little over 3 oz. after use, and we use it pretty regularly every other day. I used to test everything every day, then got accustomed to what it needed. With my new TF-100 I decided to review my methods which prompted the question.

I will say this about the ozonator. I believe it causes the PH to raise because that has been a problem since day one. :/

I agree with you about the fact that it's only treating the water and can't affect pathogens on the surface, and in that case it must be that they can never get a foothold. Thank you for your informative post on this subject.

 

[cowboycasey]

so I went through exactly what you are going through and this is what I found out... If I am wrong anyone please correct me

My ozonater runs 24/7 also, what I have read and confirmed like you is when I use bleach or any king of chlorine the ozone kills it... When I first got my hot tub they stated to put 1 inch bromine tabs in the filter ( there is an opening it gets loaded into) it was suppose to be used as a "backup" if the ozone ever went out... ozone does nothing to bromine and will last...

I started using bromine as the primary and the ozone as the backup by putting 4 bromine tabs in and checking with the TF100 for FC, i can get it to about 3PPM FC on 2 holes showing in the filter..

this is kind of what the inside of my filter looks like, yours should be close to the same... the bromine is placed inside the tube
http://www.amazon.com/Pentair-R172540-Dispenser-Replacement-Cartridge/dp/B004VU981W

 

[chem geek]

The ozonator causes a rise in pH not from the ozone itself but from the aeration it produces since the ozonator puts out mostly air into the spa. Having your TA be lower (closer to 50 ppm) and using 50 ppm Borates would help if you aren't doing that already.

As for chlorine before a soak, people usually start off with a low 1-2 ppm FC so that they don't notice much chlorine during their soak. It sounds like in your case the chlorine is getting to zero between soaks (mostly likely because of the large amount of ozone) so you're adding some chlorine beforehand to be on the safe side during the soak when presumably the ozone if off at least when jets are running. Technically you should add enough chlorine after each soak to still have a small residual for the next soak, but with your powerful ozonator that may need a lot of chlorine. Given the ozone on all the time, what you really have is more of an ozone spa where chlorine is mostly for during the soak. It's too bad you can't regulate the ozone on-time better.

If the ozonator is running all the time, then there is probably residual ozone in the bulk spa water and that would kill pathogens on surfaces, but as I noted it will also outgas and oxidize the spa cover faster. It hopefully shuts off when you use the spa; otherwise your breathing ozone is not good for you long-term. If your spa cover were not degrading and you were getting growth on spa surfaces, then I would have said that your ozonator had a de-gasser to prevent any ozone from getting into the bulk spa water, but that doesn't seem to be this situation.

As for ozone and bromine, they DO interact just as with chlorine, but ozone also produces more bromine from bromide. The net result when you have some bromide bank (either added initially from sodium bromide or created over time from spent bromine tabs) is that ozone produces bromine. However, it also uses the bromide bank up over time by converting some bromine to bromate (the same happens with chlorine where most becomes chloride but some becomes chlorate).

 

[cowboycasey]

@chem geek, you said what I wish I could have

That makes complete sense, thanks for the explanation