Filtration for a new indoor swim spa

[codybear]

Installed an indoor fiberglass swim spa and I'm finally getting around to plumbing the thing. Pool manufacturer provided the 1 hp pump, 75 sq. ft. cartridge filter and the optional 0.35 g/hr ozonator (0.70 g/hr if I use a dryer). After getting everything, I researched ozone and see that you still need chlorine and the ozone is only effective on the filtered water. Of course, with the oversized pump, it will only need 30 minutes for one turnover, so it became clear that I was being guided by a pool manufacturer that knows nothing about filtration systems.

I do have some experience with an indoor pool this size, but I always had trouble with CC with a very low use pool. But this is a future thread and only explains the logic of buying the ozonator.

Anyway, the pool has no jets, no water feature, no vacuum requirements and just needs a filtration system. My current thought is to ditch the 1 hp pump and replace it with a 1/8 hp Waterway Iron Might, which would cost about 40 cents a day to run 24/7 and plenty of turnovers. My first thought was a dual speed 3/4 hp, but I started to doubt I would ever run it at full speed. The only downside I can come up with using the small pump is the effectiveness of the skimmer. Again, this is a low use pool to be used almost exclusively by myself so that may not be as important.

Does anyone see anything wrong with using a 1/8 hp pump on a 2,600 gal. pool?

My next concern is the ozonator. I'm not sure if I should bother installing it or not. I know I would need an air dryer and contact chamber to have any effect at all. I'm concerned about CC with the indoor pool from past experience, but maybe having some CYA (yes, I have been reading this site) will help. I thought about using a SWG with the ozonator, because of possible benefits after reading someone's patent, but Richard (chem geek) pointed out the flaws with the equations. And I also see that salt can cause corrosion in some cases. So, here I am sitting with this paper weight (ozonator) trying to figure out is it worth it or not to install.

Other info: pool temp will be 79-80 degrees and most likely be using a floating cover to reduce evaporation. It also has a titanium heat exchanger.

Any suggestions about pump size, ozinator and/or SWG would be appreciated.

Jamie

 

[chem geek]

My next concern is the ozonator. I'm not sure if I should bother installing it or not. I know I would need an air dryer and contact chamber to have any effect at all. I'm concerned about CC with the indoor pool from past experience, but maybe having some CYA (yes, I have been reading this site) will help. I thought about using a SWG with the ozonator, because of possible benefits after reading someone's patent, but Richard (chem geek) pointed out the flaws with the equations. And I also see that salt can cause corrosion in some cases. So, here I am sitting with this paper weight (ozonator) trying to figure out is it worth it or not to install.

Welcome to TFP!

The corrosion concerns for the SWG could be mitigated just as they can for an outdoor SWG pool so I wouldn't have that as a particular concern. Having some form of supplemental oxidation will likely be required to keep down CC unless your ventilation system is exceptional, but since you will be having your pool covered a lot of the time that really wouldn't help that much anyway because you will be limiting outgassing. So you really need something to get rid of organics in the pool and there are several options: ozone, non-chlorine shock (MPS), enzymes, UV. Technically, UV isn't an oxidizer but it does break down some organics and chloramines as well. I know of at least a couple of people reporting on this site who had indoor pools where a UV system helped keep CC and odors down.

If the ozonator was known to be an effective one, then that would be a reasonable choice, but it sounds a bit iffy. They can certainly be effective when they are designed and sized correctly. Can you point me to the post you saw where I saw a flaw in equations for SWG and ozone? I don't recall that.

 

[codybear]

The post I'm referring to is here

Your reply is regarding patents by Joseph Gargas, who is well respected in the aquarium industry.

 

[chem geek]

Thanks. I just updated that post with information I received in the interim regarding this paper (that refers to this paper) that shows that ozone reacts with hypochlorite ion to produce 77% chloride ion and 23% chlorate ion, but no chlorine dioxide.

 

[codybear]

Ok, my chemistry is a little rusty. Is liquid bleach added to the pool just as good as adding a SWCG? I have a DIY liquid dispenser (old aquarium equipment) that can add bleach. It will drip in bleach over a given period.

Assuming the ozone added is going to be lower than the recommendation by the paper you had linked, any suggestions on level of FC and CYA? I suspect I will get some benefits with the ozone added, but if it just oxidizes the CC, I would be happy.

Jamie

 

[iPhone]

Ok, my chemistry is a little rusty. Is liquid bleach added to the pool just as good as adding a SWCG? I have a DIY liquid dispenser (old aquarium equipment) that can add bleach. It will drip in bleach over a given period.

Assuming the ozone added is going to be lower than the recommendation by the paper you had linked, any suggestions on level of FC and CYA? I suspect I will get some benefits with the ozone added, but if it just oxidizes the CC, I would be happy.

Jamie

Sounds great to swim indoors. Have you thought about getting rid of the Chlorine issue completely? You could install a Water Doctor and then only need a few of gallons of Clorox a year.

My pool is 33K gallons and I only use a little over 3 quarts of Clorox a week (one quart treats 10,000 gallons when using a Water Doctor). The Clorox is only being used as an Oxidizer.

 

[chem geek]

Ok, my chemistry is a little rusty. Is liquid bleach added to the pool just as good as adding a SWCG? I have a DIY liquid dispenser (old aquarium equipment) that can add bleach. It will drip in bleach over a given period.

Assuming the ozone added is going to be lower than the recommendation by the paper you had linked, any suggestions on level of FC and CYA? I suspect I will get some benefits with the ozone added, but if it just oxidizes the CC, I would be happy.

Jamie

Yes, an SWCG produces identical chlorine as using bleach or chlorinating liquid. Some people use The Liquidator (with a 3/8" upgrade) or a peristaltic pump so sure, you should be able to use your liquid dispenser if it is designed to handle high chlorine levels.

The ozone will be a supplemental oxidizer and while it has use in residential spas used every day, most residential pool ozone systems are woefully undersized and poorly designed. Nevertheless, for a small indoor pool it might be OK -- make sure it doesn't produce too much ozone getting into the bulk water and then outgassing -- you don't want to breathe it (it's like smog). It's more common for people to use UV systems indoors and these do control CC.

As for the FC/CYA level, there is no residual from either ozone nor UV in the bulk pool water so you still need enough chlorine to kill pathogens and prevent algae growth even on pool surfaces where there may be little water circulation. Since your pool is indoors, it might be able to use the SWCG level of an FC that is around 5% of the CYA level, but mostly because your chlorine loss should be low so you should be able to maintain it more consistently. If you wanted to lower the chlorine level a little more, then there are supplemental products you could use to prevent algae growth, but these are extra cost or have side effects (PolyQuat algaecide, phosphate remover, copper ions, 50 ppm Borates). Of these, on this forum we only recommend either weekly PolyQuat or 50 ppm Borates, though chlorine by itself can prevent algae growth.

 

[chem geek]

Have you thought about getting rid of the Chlorine issue completely? You could install a Water Doctor and then only need a few of gallons of Clorox a year.

My pool is 33K gallons and I only use a little over 3 quarts of Clorox a week (one quart treats 10,000 gallons when using a Water Doctor). The Clorox is only being used as an Oxidizer.

The Water Doctor by Intex is a copper ionizer system. It is NOT a sanitation system. Copper ions not only kill too slowly, but they do not kill nor even inhibit any fecal bacteria AT ALL. This is because pathogenic fecal bacteria live in your gut (controlled by more numerous "friendly" bacteria) and the copper ion level in normal blood serum is 0.7 to 1.5 mg/L (ppm) so such bacteria have mechanisms for living in such an environment that has a higher concentration of copper ions than your pool. Also, copper ions kill other bacteria slowly and are not very effective against viruses, protozoa, oocysts, etc. See this post for more details about metal ion kill times with references to peer-reviewed papers in respected scientific journals.

Copper ions are not EPA-approved as sanitizers or disinfectants, only as algaecides. This is because metal ions do not kill quickly enough (or at all, in the case of copper against fecal and blood-borne bacteria) to pass EPA DIS/TSS-12. Also, all NSF Standard 50 approved ionizer products require at least 0.4 ppm chlorine (or 0.8 ppm bromine).

Copper ions at sufficiently high levels will kill algae, but there is the risk of metal staining especially of plaster surfaces and of blond hair turning greenish if the pH gets up too high or the copper ion concentrations get too high. One quart of 6% bleach in 10,000 gallons is only 1.5 ppm Free Chlorine (FC) so will not be nearly enough for sanitation for a week -- more like one day if the pool is exposed to sunlight. So while the water may remain free of algae due to the copper, it is most certainly not sanitary. Of course, its just a probabilistic risk, not a certain one.

 

[codybear]

Sorry for the lapse, for some reason, I didn't get the email notification to the replies.

My fish tank pump is like the a peristaltic pump. I use a tube that is somewhat resistant to chlorine and replace it every so often. I'll need to find one that is more resistant or at least have the non-compressible part be chlorine resistant.

A question about the liquidator, is it a problem of feeding the chlorine before the ozinator? Will the ozinator destroy the newly introduced chlorine?

 

[chem geek]

You should put The Liquidator feed after the ozonator. Ozone will react with chlorine to produce chloride salt and chlorate ion. It may not get rid of all the chlorine, but why waste any? Even putting it after will still lose some chlorine since there will still be some ozone, but it will be better.