Circulation Pump - are they truly a cost saver?

[Wisoki]

Incorrect, the exact same mazi injector is used.

That's where the misconception comes in. Even though you're getting more flow with the 2-speed pump than the circ pump you're not getting more ozone and you really don't want more as all you'll do is have a big off-gas problem. A spa with a circ pump uses a different injector than one with a 2-speed pump as the orifice size has to change to compensate for flow.
Bottom line, you get much more ozone mixed with the water in a spa with a 24/7 circ pump.  

[Spatech_tuo]

Incorrect, the exact same mazi injector is used.

Actually it is correct, as there are different colored Mazzi injectors out there. The colors denote the orifice size at the intake as the flow difference between a circ pump and a 2-speed pump creates varying venturis therefore requiring a different orifice size to control he amount of ozone being drawn in. If you're only dealing with 2-speed pumps you probably only use one type but a circ pump does require a different mazzi than a 2-speed pump if you want to match the systems properly.

[empolgation]

Well the 24 hour circulation pump moves water through the chamber more slowly. If a 24/7 pump moves the contents of the tub 10 times a day and intermitent jet pumps move the contents of the tub 60 times a day, then:
 
1) If the contact chambers are equal
2) If the ozone output is equal
 
then the water in the contact chamber of a tub with 24/7 pump gets 6 times the contact time than another tub.

I think you meant to say 6 times less, no?

If the water is shooting through the chamber 6 times faster it will be in the contact chamber 1/6 of the time of a slower pump.

The big assumption with this analysis is that all of the water moved through the jet pump moves through the ozonator chamber. This is wrong. For example, with one system I am familiar (through obsevation of equipment), water coming from the filters through the pump gets diverted into 2 directions, ~ 1 1/2 inch pipe to the heater and ~ 1/2 inch tube to the contact chamber, so somewhere around 1/8 of the water flows through the contact chamber.

The question/consideration of volume and water movement with respect to ozonation effectiveness would mostly apply to the off-gas coming out of the ozonator jet. The greater the water movement in the tub the greater the chance of putting it to use before it reaches the surface.

As I've said before with the legal concentration of ozone allowed in any spa the differences between the two methods are probably insignificant. As Zz concurred, no specs, no data... only time will tell.

[Starlight]

The question/consideration of volume and water movement with respect to ozonation effectiveness would mostly apply to the off-gas coming out of the ozonator jet. The greater the water movement in the tub the greater the chance of putting it to use before it reaches the surface.

As I've said before with the legal concentration of ozone allowed in any spa the differences between the two methods are probably insignificant. As Zz concurred, no specs, no data... only time will tell.

First off, I know of NO hard data on ozone performance in spas, so we're all really guessing at this point.  Let me correct one misconception-- bubbles are NOT dissolved (aqueous) ozone and are therefore irrelevant to discussions about oxidizing/sanitizing. My take, as someone who has done a fair amount of lab chemistry work: you'd want a continuous injection of ozone with a flow rate slow enough to ensure:good contact chamber time and minimization of turbulance and high-speed impacts with nucleating material that would cause the ozone to outgas from solution.  Think of pouring a soda quickly over ice and how much foam is created.  Even if the ozone stays in solution when you move the water quickly, you would effectively be diluting the ozone in a greater volume of water.  You won't find many pathogens in a teaspoon of straight bleach, but dilute that tablespoon in a spa and its sanitizing power is lost. Because the half-life of ozone is so short and the rate of ozone production relatively low compared to water volume, any dissolved ozone would rapidly be depleted from the water and therefore the water will continuously be capable of accepting more ozone.   If additional ozone is not continuously supplied, you aren't taking full advantage of the ozonator. Some assumptions I've made:
1.  Ozone is actually oxidizing and/or sanitizing in meaningful amounts
2.  Demand for ozone always exceeds supply
3.  Ozone is produced at a fixed rate

Until someone does some good studies on use of ozone in spas, how an ozonator is best used will come down to personal belief.

Starlight

[Mendocino101]

Starlite,

I appreciate your comments. Are you saying that for example that if you are using a high flow system.( 2 speed pump) and moving more water but doing so with an adequate contact chamber say 20 ft or greater than it is effective ? or are you saying that for spa use the slower moving circ pumps does offer better ozone zanitation....or that both are truly still up for debate as to which is significantly more effective.

[empolgation]

First off, I know of NO hard data on ozone performance in spas, so we're all really guessing at this point....
 
Until someone does some good studies on use of ozone in spas, how an ozonator is best used will come down to personal belief.

Thank you for your input Starlight!!

[empolgation]

... for example that if you are using a high flow system.( 2 speed pump) and moving more water but doing so with an adequate contact chamber say 20 ft or greater than it is effective ? or are you saying that for spa use the slower moving circ pumps does offer better ozone zanitation....

Mendo keep in mind that the flow through the chamber in a 2 speed pump system is not such "high flow" because only a portion of the flow gets diverted to the chamber.

[Mendocino101]

Mendo keep in mind that the flow through the chamber in a 2 speed pump system is not such "high flow" because only a portion of the flow gets diverted to the chamber.

Are you saying this is true of all makers, using the "hi flow" system....I do not know the answer...just wondered...I just spoke with a friend of mine who shared with me that in his opinion Ozone works great for the single guy or couple that travels or uses the tub more lightly....and does offer some real benefits in the aid of zanatioan.....but for a family who uses the tub alot...its effectiveness is much less benifical...

[empolgation]

Are you saying this is true of all makers, using the "hi flow" system....

Nope - I sure ain't, but considering all the great insight gleaned from this thread I sure wouldn't consider one that doesn't.

Whether that's the case or not for a particular tub is a critical question for those who care about what they are paying for.

[ebirrane]

I think you meant to say 6 times less, no?

No. That was the point. It's 6 times more because it is moving 6 times slower. The slower you move past something, the longer you are in contact with it.

[ebirrane]

Mendo keep in mind that the flow through the chamber in a 2 speed pump system is not such "high flow" because only a portion of the flow gets diverted to the chamber.

I think he meant compared to a less powerful 24/7 pump.  Or are you saying that a 24/7 dedicated circulation pump actually moves more water through a contact chamber than tubs which use the jet pump?

[ebirrane]

On tubs with a 24/7  circulation pump is it guaranteed that all water being pulled from that pump is going through the contact chamber?

Empolgation stated that in at least one brand of tub only 1/8 of the water pulled from the pump on clean cycle is going through the contact chamber.

On the assumption that:

1) a spa has x gallons of water
2) a 24/7 pump moves 10X a day
3) a 24/7 pump has all of its water going through the contact chamber.
4) a jet pump on clean cycle moved 60X a day
5) 1/8 of the water on a jet pump clean cycle goes through the contact chamber

then a tub with a 24/7 pump moves 10X of water through the contact chamber

And a tub with a jet pump moves 60X / 8 of water through the contact chamber, or 7.5X.

Even though the jet pump method moves less water past, I am assuming it still moves the water at a faster speed than the 24/7 pump water. Is that correct?

Can some actual hot tub techs chime in on some other brands of tubs and how they feed the contact chamber?

Also, I think that we assume that ozone is somehow evenly distributed throughout the chamber. It that true? Is ozone injected across the whole 20'?  It seems like the shorter the contact chamber the easier it is to get a more uniform distribution of ozone.

[Starlight]

Starlite,

I appreciate your comments. Are you saying that for example that if you are using a high flow system.( 2 speed pump) and moving more water but doing so with an adequate contact chamber say 20 ft or greater than it is effective ? or are you saying that for spa use the slower moving circ pumps does offer better ozone zanitation....or that both are truly still up for debate as to which is significantly more effective.

As I said earlier, we really don't know.  But, my a.s.s.umption (software altering word unless I added periods) is that the actual amount of ozone produced is the real limiting factor.  If true, it really wouldn't matter how that ozone was dissolved into the water(hi/low speed, large/small contact chamber) as long as both methods dissolved equal amounts into the water.  The actual effects of the ozone (because of its short lifetime) would probably only be observed in a small "slug" of water that is in the contact tube and near where ozone is introduced into the tub.  As emplogation points out, just because your pumps move more water doesn't mean that you are moving that water through the ozone system.  If you *could* move that water through the contact chamber AND if it resulted in a higher percentage of gaseous ozone dissolving into the water, then there could be advantages to that type of setup.  The other thing we don't know is if ozone from this generation of systems is effective as a sanitizer.  If it is, then you'd want ozone 24/7 to help kill the reproducing bacteria; if it isn't, then all ozone does is burn up other organic matter and as long as your "slow & continuous" and "fast & concentrated" systems both delivered and made effective use of the same quantities of ozone, they'd be equivalent.

Your friend's point about the effectiveness of ozone suggests that the amount of ozone generated--or at least the ammount able to be dissolved into the water--is the limiting factor.  If the current ozone systems can oxidize the equivalent of "4 user-hours" per day of body oils, etc., one would find the most dramatic reduction of spa sanitizer demand in a spa where the spa usage fell at or below "4 user-hours"--one person for four hours, two people for 2 hours, etc.  If the whole family uses the tub, then the ozone is still taking care of its "four user-hours" of stuff, it just isn't as apparent when the demand is for a much higher "user-hours" of stuff introduced into the spa.

Starlight

[Spatech_tuo]

On tubs with a 24/7  circulation pump is it guaranteed that all water being pulled from that pump is going through the contact chamber?

Yes.

[soon2float]

Wow, I cannot believe the controversy this topic created. It seems the only agreeable conclusion here, by so many of you who I would feel are experts on tubs, is that there does not seem to be any documentable proof as to the actual effectiveness of Ozone in hot tubs.

Logically, one would assume that Ozone has some beneficial effect in hot tubs or companies would not want to increase their cost of a tub, so studies must be available some where. Are there any chemical engineers out there who are aware of any research papers written on the subject that might help us resolve these questions here?