New indoor swim spa and hot tub..best water treatment method

[Kdot]

Ok...we are having a swim spa and a hot tub installed in a not-yet-constructed sunroom which will be attached to the house. Of course, the windows will be operable for ventilation and we are planning on having an in-wall dehumidifier installed. The sunroom will be heated and air conditioned.
I have been struggling with deciding upon a water treatment method. Both units are self-contained and will come equipped with their own ozonators. I am aware of the risks with using ozonators especially in an indoor application such as ours. Furthermore, my young son has some history of asthmatic issues. So, we are planning on not using the ozonators except for instances in which we want to run in them temporarily to address any issues ( a cold in the house, a pool/spa party yielding increased usage, etc). In these events, we will run the ozonators with the windows open.
But, for daily on-going treatment, without the ozonator, I am struggling with finding a manageable yet effective method while avoiding "that smell" with our indoor application.
I have read about enzyme methods, but I am not completely sold on their sanitation efficiency. I know bromine is effective, but I am a little concerned about the odor. The same goes for chlorine. I am also aware of the mineral methods (Nature2), but I understand that they aren't really suitable for larger pool of water at higher temps, such as the swim spa. I have heard of ionizers but don't know much about them.
So, with the two units (swim spa and hot tub), our indoor application, and the potential sensitivity of my son to ozone...I really don't know which way to go.
Any advice would be really appreciated.
Kathleen

 

[JohnN]

Re: New indoor swim spa and hot tub..best water treatment me

Chlorine is by far the best bet. If you properly maintain the pool, you won't get any irritation or get "that chlorine smell". I don't have an indoor pool or spa, so I will let someone who does have one give you more detailed advice.

 

[chem geek]

Re: New indoor swim spa and hot tub..best water treatment me

One of the main reasons many indoor commercial/public pools smell of chlorine is that they do not use Cyanuric Acid (CYA) in the water so the chlorine outgasses faster and reacts with the ammonia and organics from higher bather-load to form more volatile and irritating nitrogen trichloride that is the worst of "bad pool smell". I suggest you add CYA to your indoor swim spa at least at a low level of 20 ppm (not more than 30 ppm) and then see how it goes maintaining 2 ppm FC (if your CYA is 20 ppm; 3 ppm FC if it's 30 ppm CYA). You should have minimal smell that way.

If you notice CC rising or begin to notice a "bad" smell, then you can see if the ozonator will clear that out. Your approach sounds reasonable. Keep us posted.

 

[Donldson]

Re: New indoor swim spa and hot tub..best water treatment me

Chem geek is right on as to the best way, especially saving the ozone only if you have CC problems. With just a little CYA you can keep the chlorine buffered while still only keeping 2-3 ppm of free chlorine. I think this method will help keep everything in check, especially for your son.

I will mention that any ionizers or mineral systems will introduce metals in to your water and could cause staining. The cons of these far outweigh the minor benefits so they are generally frowned upon around these parts. I'm not a fan of ozone either, but in your case this could occasionally help burn off some CC that would normally be burnt off by the sun in an outdoor pool.

 

[Kdot]

Re: New indoor swim spa and hot tub..best water treatment me

Ok...so I probably need to get over my negativity towards chlorine, yes?
If we can control the chlorine smell and it is effective then it may be the best approach.
Now, for another newbie question, would chlorine be better, given my indoor application, than bromine?

 

[harleysilo]

Re: New indoor swim spa and hot tub..best water treatment me

What type of maintenance will you be able to give your pool and spa? You won't have debris to net out, and their won't be anything to vacuum up. Will you be able to add chemicals daily to it? Every other day? Do you travel a-lot?

I would suggest starting with liquid Chlorine. Also known as bleach. Regular old bleach, nothing scented or super concentrated. You will be dosing manually, most likely daily. This will allow you to get a feel for how much your particular pool and spa use. At some point you could potential automate this process.

When you say your equipment is self contained you mean there will be no "pump room", no runs of pipe to and fro, all equipment will be hidden underneath the pool/spa and enclosed, right? I don't know how you would automate in that circumstance.

 

[chem geek]

Re: New indoor swim spa and hot tub..best water treatment me

Now, for another newbie question, would chlorine be better, given my indoor application, than bromine?

Yes, chlorine would still be better for an indoor application. It's a better disinfectant and oxidizer, can be moderated in its strength by CYA, is less expensive, and the disinfection by-products are less harmful (in general, the brominated organics are more mutagenic/genotoxic than the chlorinated ones) though at the levels in a low bather-load pool the risks are very low for either.

 

[Isaac-1]

Re: New indoor swim spa and hot tub..best water treatment me

You would be surprised how much stuff has to be vacuumed out of an indoor pool

 

[Kdot]

Re: New indoor swim spa and hot tub..best water treatment me

So, chlorine would be a preferred method over bromine for both indoor swim spa and hot tub?
As far as maintenance, anything that would require daily maintenance would be tough for me to manage consistently on a long-term basis...with a 3 yr old, a full-time job, and a too-long commute. I would like to think that I could attend to spa chemistry every day, but REALISTICALLY it probably won't happen.
Does a chlorine regimen require daily maintenance?
If so, is there another effective method for both swim spa and hot tub housed indoors?

 

[chem geek]

Re: New indoor swim spa and hot tub..best water treatment me

The chlorine loss rate in an indoor pool is fairly low so that you probably could dose twice a week instead of every day. In a hot spa, however, with chlorine you'd have to dose every day or two unless you had higher chlorine swings between soaks. Ironically, if you don't use the spa every day or two, then an ozonator results in a higher chlorine loss since ozone reacts with chlorine. So for a spa, using bromine tabs can be less maintenance, but there are other alternatives for a spa such as a saltwater chlorine generator, the ControlOMatic TechniChlor (in a spa with its smaller water volume it uses around 2000 ppm salt). You can, of course, have a saltwater chlorine generator for your indoor pool as well (those usually require around 3000 ppm salt). Another alternative for your indoor pool would be The Liquidator.

 

[Kdot]

Re: New indoor swim spa and hot tub..best water treatment me

In conducting some additional research, I have learned that the use of chlorine as a water treatment method for indoor spas can be corrosive to the actual building envelop...the hardware, nails, screws, and joist hangers and electrical wiring, outlets, and fixtures, all due to chlorine off-gassing. Even with installing active ventilation, this is a bit scary!
I understand that bromine does not off-gas such as chlorine...so, why would chlorine be a better choice for an indoor environment?
I did find recommendations on a site for contractors (building not pool/spa) recommendations for non-chlorine treatments, such as: Pristine Blue, Baquacil, and EcoSmartePool for indoor environments. What are the thoughts on these issues and these alternative methods.

 

[JohnN]

Re: New indoor swim spa and hot tub..best water treatment me

I'll let someone with more indoor pool experience comment on the off gassing. I will comment on the alternatives. Pristine Blue and EcoSmarte add metals (specifically copper) which will cause staining and can turn hair green. Just search for copper staining to see why we don't recommend them. Baquacil is expensive, and from what I understand it seems almost impossible to keep a pool clear. Take a look in the Baquacil Use and Conversion forum to see all of the problems people have with that.

 

[Donldson]

Re: New indoor swim spa and hot tub..best water treatment me

I don't know for sure about the potential for corrosion, especially in a properly maintained pool, but I would bet that what you read are exaggerations at the least. Much of these statements are often made by people who have a financial interest in these "chlorine alternatives." Any system must use either chlorine, bromine, or baquacil anyway, you cannot sanitize a pool by putting copper in it. You can definitely cause problems by putting copper in it though.

Bromine is an acceptable alternative overall, not as good as chlorine in almost all respects but can still be a decent sanitizer. Baquacil is... not a very good alternative.

In the end, why is chlorine recommended for virtually every pool? Because it is the least expensive and the most effective. When used properly it has the least problems. Bromine is more expensive and slightly less effective. Baquacil is most expensive and least effective. All of the alternatives you listed require chlorine to be used, are more expensive than chlorine and offer no improvement in performance. Every alternative to chlorine costs more for inferior performance. That is why it is universally recommended.

 

[chem geek]

Re: New indoor swim spa and hot tub..best water treatment me

You are comparing traditional indoor pools using chlorine with no CYA and that's not what we are talking about. Chlorine outgasses more than bromine when there is no CYA in the water to moderate chlorine's strength. When one uses CYA in the water and maintains an appropriate FC/CYA ratio, the outgassing rates for chlorine and bromine are fairly comparable at worst or where chlorine is far better (less outgassing) at best.

The idea that bromine outgasses less than chlorine is again one of those deceptions of the pool industry that is simply not true. Someone looked at the Henry's Law constants (see this link) for MOLECULAR bromine vs. chlorine and concluded that bromine outgasses faster. Molecular bromine (Br₂) has a Henry's Law constant of 0.76 M/atm while molecular chlorine (Cl₂) has a Henry's Law constant of 0.095 M/atm so at equal concentrations (that is, equal "M", but in ppm, bromine would be 2.25x higher), chlorine is 0.76/0.095 = 8 times more volatile (a smaller M/atm is a more volatile compound, at least in terms of equilibrium concentrations).

HOWEVER, there is very little molecular bromine or molecular chlorine in the water at pool pH and what really outgasses is hypobromous acid (HOBr) and hypochlorous acid (HOCl). The Henry's Law constant for hypobromous acid is not well determined, varying from 1.8 to 6100 M/atm (depending on source), while for hypochlorous acid it is 660 M/atm. So it is not at all clear in this situation which one definitively outgasses faster.

HOWEVER, the above has no CYA. The actual hypochlorous acid concentration in the pool with CYA is roughly the same as a pool with only 0.1 ppm FC and no CYA. So it's at least 10 times lower than the concentration of hypobromous acid and outgasses slower as a result. The net result is that in the worst case chlorine outgasses at about the same rate as bromine, but more likely it outgasses an order of magnitude or more slower.

The other issue for outgassing and corrosion is with chloramines and here again in indoor pools without CYA and with higher bather-load there can be too much very volatile and irritating nitrogen trichloride (NCl₃, 0.1 M/atm) produced. That's a particular problem in indoor commercial/public pools and most associated with "bad pool smell". Residential pools are typically low bather-load and again with CYA in the water there is very little nitrogen trichloride produced and instead there is a small amount of monochloramine (NH₂Cl, 94 M/atm) and dichloramine (NHCl₂, 29 M/atm) that is temporary and would show up as CC (which is often <= 0.2 ppm so very low in concentration). Most CC is chlorourea and is not volatile.

Some residential indoor pools use pool covers, often automatic electric safety covers, but mostly to minimize water evaporation and humidity (though obviously helps with outgassing as well), especially if the pool room is not in a separate building in terms of air circulation. Also, you normally have air circulation and venting or dehumidifiers since by far the greatest source of damage is from humidity and mold, not from chlorine corrosion of metal (again, in pools properly managed with some CYA).