UV system, recall and options - what to do

[isabelo]

As part of the pool build package, the PB convinced us to get a UV system to take care of parasites that are not getting killed by chlorine. He said UV systems will also allow less chlorine requirements. A year later, PB called to unplug the UV unit because of a recall due to arching and possible fire. The Trident UV corporation was bought out by Paramount Pools and they will not be responsible for any UV unit sold before they took over. The recall made me and my wife concerned about our safety especially future troubles even when the recall's approved kit is installed. So now we are considering taking the UV system completely out thus taking a loss (PB will not refund).

I talked to the distributor that handles the recall fix kit to owners. He told me the recall fix kit only provides an aluminum shield covering the area where the arching occurs and other wiring replacements, but arching may still occur. He also mentioned another alternative, but will cost me additional whole sale cost and this will give me a new Paramount UV system with a better ballast and UV bulb configuration that will no longer cause arching.

Now the question: Will it be worth replacing the UV system (or even just taking the government approved recall fix kit) and continue using the UV system as a secondary sanitation? Or do you think I should just have it completely taken out since Chlorine is good enough to do the sanitation work and not worry about parasites that chlorine cannot handle?

 

[mas985]

Take the recall fix kit, repair the unit, then sell it on eBay. You don't need a UV system.

 

[chem geek]

The UV is not necessary when using chlorine. In practice, the only pathogen that chlorine does not effectively handle is the protozoan oocyst Cryptosporidium parvum. See the chart in this post that shows 3-log reduction (99.9% kill) times when the Free Chlorine (FC) level is roughly 10% of the Cyanuric Acid (CYA) level. There is also this table from the CDC (the protozoan oocyst Toxoplasma gondii is also not handled by chlorine but is very rare).

Protozoan oocysts are not freely in the environment and instead come from diarrhea releases from animals (including humans) who are infected and sick. So unless you throw a pool party and a sick individual with Crypo and diarrhea attends, you won't be seeing this pathogen in your pool. It's mostly seen in some public pools but even then the rate of outbreaks per pool is roughly 0.004% per year (122 outbreaks over 10 years in 300,000 treated commercial/public pools) so still pretty small though outbreaks usually involve many people since they aren't detected right away. So for commercial/public pools having a UV or ozone system to limit the size of a Crypto outbreak makes sense and is in the CDC Model Aquatic Health Code (MAHC), but for residential pools it doesn't make sense unless one is extremely paranoid and doesn't control or trust who gets into their pool or spa.

As for lowering chlorine requirements, that is absolutely not true. The UV system does nothing to prevent pathogen growth nor algae growth on pool surfaces or for any pathogens that don't get circulated so you need a residual chlorine level to handle that regardless. Also, UV breaks down chlorine though for the typically woefully undersized systems used in residential pools you'd likely not notice that effect.

 

[isabelo]

The UV is not necessary when using chlorine. In practice, the only pathogen that chlorine does not effectively handle is the protozoan oocyst Cryptosporidium parvum. See the chart in this post that shows 3-log reduction (99.9% kill) times when the Free Chlorine (FC) level is roughly 10% of the Cyanuric Acid (CYA) level. There is also this table from the CDC (the protozoan oocyst Toxoplasma gondii is also not handled by chlorine but is very rare).

Protozoan oocysts are not freely in the environment and instead come from diarrhea releases from animals (including humans) who are infected and sick. So unless you throw a pool party and a sick individual with Crypo and diarrhea attends, you won't be seeing this pathogen in your pool. It's mostly seen in some public pools but even then the rate of outbreaks per pool is roughly 0.004% per year (122 outbreaks over 10 years in 300,000 treated commercial/public pools) so still pretty small though outbreaks usually involve many people since they aren't detected right away. So for commercial/public pools having a UV or ozone system to limit the size of a Crypto outbreak makes sense and is in the CDC Model Aquatic Health Code (MAHC), but for residential pools it doesn't make sense unless one is extremely paranoid and doesn't control or trust who gets into their pool or spa.

As for lowering chlorine requirements, that is absolutely not true. The UV system does nothing to prevent pathogen growth nor algae growth on pool surfaces or for any pathogens that don't get circulated so you need a residual chlorine level to handle that regardless. Also, UV breaks down chlorine though for the typically woefully undersized systems used in residential pools you'd likely not notice that effect.

Thank you chem geek. Your inputs made our decision easier. We'll remove the UV unit completely out, besides, I'll save ~$240.00 every 18 months not buying/replacing new UV bulbs.

 

[chem geek]

I should also point out that if someone with Crypto did use your pool or spa while you were in it and had a diarrheal release, the UV system isn't going to protect you from the person-to-person transmission of disease that could result. The UV just prevents that pool from continuing to be a potential infection source over weeks or more until someone figures out that people are getting sick from the pool due to Crypto. So really, the only scenario where UV would be helpful is in the very unlikely scenario one where a person sick with Crypto uses your pool and then the next day or so you use it.

The CDC MAHC has a formula for the minimum flow rate through the UV system in order to get a reduction in Crypto oocysts from the 100 million in a single release down to a concentration of one oocyst/100 ml. The formula is Q = V x {[14.8 - ln(V)] / (60 x T)} which with your 14,000 gallon pool and using the 9 hour time they recommend (assuming the pool venue is closed for 12 hours in a 24 hour period) so 14000 x {[14.8 - ln(14000)] / (60 x 9)} = 136 GPM. I'm sure your pump flow rate isn't that high and may be roughly half that or 68 GPM which implies that it would take 18 hours of pump circulation (with UV on) time to get the Crypto oocyst concentration down to a level where getting infected is unlikely. If your flow rate is even lower (given your variable speed pump), then the time would be even longer.

The more practical purpose for using a UV system is for reduction of chloramines, but this is unnecessary in an outdoor residential pool exposed to sunlight. It's more applicable to indoor pools.

 

[isabelo]

I should also point out that if someone with Crypto did use your pool or spa while you were in it and had a diarrheal release, the UV system isn't going to protect you from the person-to-person transmission of disease that could result. The UV just prevents that pool from continuing to be a potential infection source over weeks or more until someone figures out that people are getting sick from the pool due to Crypto. So really, the only scenario where UV would be helpful is in the very unlikely scenario one where a person sick with Crypto uses your pool and then the next day or so you use it.

The CDC MAHC has a formula for the minimum flow rate through the UV system in order to get a reduction in Crypto oocysts from the 100 million in a single release down to a concentration of one oocyst/100 ml. The formula is Q = V x {[14.8 - ln(V)] / (60 x T)} which with your 14,000 gallon pool and using the 9 hour time they recommend (assuming the pool venue is closed for 12 hours in a 24 hour period) so 14000 x {[14.8 - ln(14000)] / (60 x 9)} = 136 GPM. I'm sure your pump flow rate isn't that high and may be roughly half that or 68 GPM which implies that it would take 18 hours of pump circulation (with UV on) time to get the Crypto oocyst concentration down to a level where getting infected is unlikely. If your flow rate is even lower (given your variable speed pump), then the time would be even longer.

The more practical purpose for using a UV system is for reduction of chloramines, but this is unnecessary in an outdoor residential pool exposed to sunlight. It's more applicable to indoor pools.

That is more very relevant info, chem geek, many thanks.

 

[Daf-Tekno]

Using ChemGeek's advice, I constructed a 2-tier timer solenoid so that my UV only comes on during use, thus saving on bulb life and chlorine reduction. He's a handy chap, ain't he..!
Daf Tekno