UV system for a small 150 gal indoor hot tub?

tfpusername

Well-known member
Apr 23, 2017
92
Las Vegas
Looking at getting a small hydrotherapy tub (150gal), and while I know that all hot tubs require SOME chlorine, I’ve heard that a UV system can reduce the amount of chlorine required by half (which is huge if you’re sitting in/inhaling this water for hours).

I would hope that with regular water changes (another reason we want a small 150gal tub), a UV system would be enough to keep the chlorine levels ultra low (1ppm? 2ppm?).

My question is - the model we’re looking at doesn’t offer a UV option, so how hard is it to retrofit an existing tub with something like this…


I have zero plumbing experience, but follow directions well.

*or perhaps we could get away with just an ozone system (the factory will install one of those for an extra 100 bucks). Or maybe ozone + UV together? Willing to spend an extra 350 bucks if it means greatly reduced chlorine levels.

Thanks for any advice.
 

jimmythegreek

TFP Expert
Bronze Supporter
In The Industry
Aug 10, 2017
3,551
Morris Cnty NJ
The ozone will be enough on it's own. It burns off the chlorine so you just dose it after a soak and ur good. Just maintain normal levels and watch the ph closely
 

RDspaguy

In The Industry
Mar 21, 2020
1,219
Cabool, Mo
Your biggest problem with that one is the flow rate. At 2gpm, even with the smallest circ pump it will have to be plumbed on a bypass. I would look for a higher flow rate on an aftermarket install.
Both ozone and uv work best on a 24/7 circulation system. Does your tub have that? Ozone and uv both provide a "low chlorine" environment, but not by reducing the need for chlorine. They both will neutralize chlorine in the water, and thereby provide you with sanitary, low chlorine water at the time of use, but still require the addition of sufficient chlorine to destroy the pathogens in the first place. It is true that both destroy pathogens exposed to them, but since these systems take dirty water from the tub, treat it, then return it to the same dirty tub, they are not a stand-alone system. They do not provide sanitation to the entire volume of the spa. Output, run time, and flow rate all play a large role in the efficiency of these methods.
I have worked on therapy tubs in pro sports locker rooms and medical facilities, as well as normal spas, that use a uv/peroxide system. It has been pointed out to me that this is not CDC approved, which I couldn't say, but that doesn't seem to stop them from doing it anyway. The 35% hydrogen peroxide used is expensive, can be difficult to get in some places, and is nasty, dangerous stuff, so do some serious research before trying that out. It is usually set up on a peristaltic pump and injector rather than being added by hand.
All that said, a properly maintained tub should not have excessive, if any, odor or chemical fumes associated with use. A period of non-use is necessary for treatment.
Do you have some (extremely rare) chlorine sensitivity or breathing problem (copd, asthma, etc.) that causes you to need a low chlorine environment?
I should also point out that most manufacturers will void your warranty for installation of any aftermarket part. You might want to check with the dealer before going too far down that road.
 

tfpusername

Well-known member
Apr 23, 2017
92
Las Vegas
All that said, a properly maintained tub should not have excessive, if any, odor or chemical fumes associated with use. A period of non-use is necessary for treatment.

That's an interesting point... What if we have them install the ozone system ($100), and just pour in a small amount of chlorine after each use? If we run the pump for an hour or so after we get out (it is NOT a continuous circulation pump), would that clean the water AND burn off the chlorine before our next use? I guess we really only care about the chlorine levels while we're sitting in the tub, so how long does it take for the chlorine to sanitize the water, then get burned off by the ozone?

We're also willing to do a partial drain/refill on a regular basis if that would help (or is a complete drain/refill the only thing worth doing?). Either way, should be easy with a 150 gal tub (and the garden hose right outside the window).

And yes, we're both very sensitive to breathing in the steam from hot tubs. Not to mention, the tub will be in a breakfast nook right off the kitchen, so we're really concerned about the smell (but if the ozone system can keep up, I guess this won't be a problem?).
 

RDspaguy

In The Industry
Mar 21, 2020
1,219
Cabool, Mo
run the pump for an hour or so after we get out (it is NOT a continuous circulation pump), would that clean the water AND burn off the chlorine before our next use?
Depends on the ozonator, injector, spa volume, and more. To my knowledge there is no study on the subject.


the tub will be in a breakfast nook right off the kitchen,
One word: ventilation. Unless you like mold and mildew.
 

tfpusername

Well-known member
Apr 23, 2017
92
Las Vegas
One word: ventilation. Unless you like mold and mildew.

Yup, we have two big windows in this corner where the tub is going, and two big fans will be blowing across the tub and out the window window. We're also pretty dry as it is here in Vegas (our bathrooms have no exhaust fans, and never had any problems with humidity).

Depends on the ozonator, injector, spa volume, and more. To my knowledge there is no study on the subject.

Well if we schedule the pumps to run their regular circulation at night (after our soak) and in the early morning, I would think that would be enough time to burn off the chlorine 'shock'? But will that be enough time for the chlorine to also 'work'?
 

RDspaguy

In The Industry
Mar 21, 2020
1,219
Cabool, Mo
The exposure time for pathogens varies with type of pathogen and fc level. Some are even chlorine resistant. But for most, at normal levels, it is a matter of hours.
 
Thread Status
Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.