UV Filter Pool Chemical Levels

[skrause]

Hello All, I have been reading posts in this forum for awhile and familiarizing myself with the rules before I posted. I created a signature with my pool specifics.
My question today is about chemical levels in my UV Filtered Pool. My understanding is that I can run my FCL as low as .5 ppm with my UV filter. This leads me to the question of CYA levels. I am currently running a CYA of 60 on an outdoor pool in Texas with full Sun all day long. I have read in this forum that under these conditions a CYA of even slightly higher levels is not unheard of, but with that high a CYA level I am worried that FCL of .5 ppm would not be adequate even with a CYA of almost zero. Does the addition of the UV filter change the math on the CYA to FCL equation? Below are my current levels. The pool is completely clear no cloudiness. I just want to make sure that no one will get sick.
FCL .05 (just added 8 fl oz of 8.25% bleach per Pool Pal to raise the level to .5 ppm after this reading)
TCL .31
PH 7.4
TA 68
CH 353
CYA 60
Thanks in advance for you assistance.

 

[JVTrain]

Welcome to TFP!

With a CYA of 60 and that low of an FC level, you're not adequately sanitizing your pool. See this chart here for the active FC level for various concentrations of CYA. Pool Water Chemistry At those levels, you don't have enough active chlorine (that which is unbound to CYA) to even kill bacteria, much less algae. Even very well designed UV systems require exposure of the pool water to the UV cell directly to kill bacteria and viruses, which does not happen often enough or fast enough even if running your pool pump 24/7 at high speed (which is also costing you money if you do). However, chlorine is everywhere in your pool, constantly battling any bacteria or viruses that might be present or introduced. Here at TFP, because the pool water must be directly exposed to the UV system for efficacy and the increased cost of installation and increased run time of pool pump to make even a minor difference in sanitation, we make no accommodations to our recommended levels for CYA/FC. UV systems do not provide enough benefit in an outdoor pool to outweigh the cost.

Your pool will develop algae unless your are using other products such as phosphate remover and algaecide very strictly and regularly. Even if you do that, you're not adequately preventing bacteria and viruses. The most cost-effective and reliable way to keep a pool properly sanitized is chlorine in the proper amounts for your CYA level.

Also... your test results appear to be pool store results, which are not recommended here either. Even if they were accurate (which many times their electronic systems are not) they are not convenient. Much easier and reliable to test at home with Taylor reagents.

 

[Chuckiechan]

What does your UV system instruction say? FC@ .05 might as well be zero.

Until you get a definitive answer, I'd suggest you get your FC up to spec's, and figure out from there how far down you can go with out having an algae bloom.

 

[tim5055]

Joel is correct. UV is registered with the EPA as a "Supplemental sanitizer", meaning you need a minimum of 1ppm residual of an EPA-registered sanitizer in the water at all times. These sanitizers include chlorine, bromine, or hexamethylene biguanide.

Pool builders sell the "dream" of less chlorine, but in practical use low chlorine levels are quickly depleted and allow algae to get a foothold and you loose control of the pool.

I see you list a ColorQ as your testing method. Please do not confuse the specificity of the results the ColorQ gives with accuracy. We have had members attempt to use the ColorQ to follow our methods and almost all have abandoned its use due to inaccuracies and inconsistencies. We even had one member test the same sample of water three times in a row and ended up with three different sets of results. Here is an example of a ColorQ post: ColorQ vs TF100

 

[skrause]

Thanks for all the great input. I will get my FCL levels up to what's recommended in the CYA chart and wait to hear from the manufacturer. I will also be ordering the TF-100 today. I do like the convenience of the ColorQ, but if it's giving me inaccurate readings then it's useless to me. I will post back once I hear from the UV Filter manufacturer.

 

[skrause]

I pushed my FCL level up to 6.5 to correspond with my 60 CYA level.
Got the following back from the UV manufacturer:
"[FONT=&quot]The CYA is to stop the sun from taking the chlorine out of the water. The minimum level of chlorine we recommend is .5 and this is adequate with Ozone because Ozone is constantly shocking the pool. However the chlorine must be check daily at these levels and things like rain, heavy winds, heavy usage, dogs stepping in and swimming in the water and other things can take chlorine out quickly. If you anticipate these conditions then you should lean toward a .8 to 1 count on the chlorine so you have a little more reserve. And don’t have to test the water as often.[/FONT]"

 

[JVTrain]

You have to decide for yourself how you want to manage the pool chemistry. The manufacturer will tell you one thing. Our methods are another. If you go to the pool store, they'll tell you another. It's your pool and you are free to manage it the way you want to as a private residential pool. If you like, you could even turn it into a frog habitat. However, trying to mix advice from TFP, manufacturer and/or pool store will only lead to confusion and frustration. TFP methods have been proven to work across thousands of pools with the best interests of the pool owner in mind. Stick with one method whatever you decide. If at a later date, you don't like how that method works, change to another but only one at a time.

 

[BuckeyeChris]

constantly shocking the pool as long as your pump runs 24/7....

 

[borjis]

holy wow! (that quote from the UV company)

It's hard to believe they'd make that statement....that's plentiful ammo for a lawsuit if someone
were to get sick possibly die from that recommendation.

 

[NeedMoreSun]

On their own site they have an article reprint:

Alternative Pool Water Sanitizers - UV & Ozone - Paramount Pool and Spas

In the section on UV it says:

"UV manufacturers and proponents point to data indicating that a properly sized system, particularly in relation to flow rate — the most important parameter in system selection — will reduce chlorine consumption by at least 50 percent, and in many situations even more."

Their own reference says "consumption" and is much different than what level is maintained. I guess in theory, if its killing off little buggers then the existing chlorine has less work. To ME this would mean less to add daily to MAINTAIN my levels. I'm saving on consumption. (I'm not saying I'd save, no clue).

However, if they are advertising "50% or better", and you take the pool store answer of a minimum of 1, you get .5. Other than their brazen advice to "count" on a reduction it sounds like it's mostly based on going back to what level should be there in the first place even without UV.

I have less consumption due to having a screen enclosure, but it doesn't mean I simply run with less

 

[skrause]

I will be sticking with the CYA to FCL ratios on this site. Especially after reading up on the Crypto Parasite... I will just look at the UV as an aid to the chlorine killing off bacteria and viruses helping to keep my water a little cleaner and clearer. I ran the frog habitat by the wife and she didn't seem interested

 

[cowboycasey]

I will be sticking with the CYA to FCL ratios on this site. Especially after reading up on the Crypto Parasite... I will just look at the UV as an aid to the chlorine killing off bacteria and viruses helping to keep my water a little cleaner and clearer. I ran the frog habitat by the wife and she didn't seem interested

That is a very good point of view and actually would agree with it, I have Ozone on my hot tub and thought the same exact way, I use the recommended levels from here and if the ozone/UV kills anything else bonus if not, its not hurting anything

My favorite saying is "knowing is half the battle"

 

[jblizzle]

But ... the UV itself is breaking down some of the FC too. Just like all the free UV from the sun does.

So having a UV system, IMO especially in the sun belt, is an added upfront cost, uses electricity which costs money, and is breaking down some of my FC (which may or may not balance with the reduced FC consumption by nasties in the water).

Just does not make sense to me in an outdoor, low use pool in areas with massive amounts of UV from the sun already.

 

[marcgr]

The UV from the UV unit is on a different wavelength than the UV from the sun. The UV from the UV unit burns very little chlorine, but it does strongly disrupt cellular matter in a way that the UV from the sun doesn't.

Over the winter I had my UV unit on for about 12 hours a day and my pool was using about 1/2 cup of bleach per day - same or less than what others report without the UV unit. So the amount of bleach that a UV unit will burn is negligible in my experience. I changed my UV program to run 4 hours a day a few weeks ago, but now that the sun is out I am up to 1/2 gallon a day...

Nevertheless, I am convinced (having looked at this a lot) that I still need to maintain an appropriate CL/CYA ratio even with the UV.

 

[trbvm]

The UV from the UV unit is on a different wavelength than the UV from the sun. The UV from the UV unit burns very little chlorine, but it does strongly disrupt cellular matter in a way that the UV from the sun doesn't.

Over the winter I had my UV unit on for about 12 hours a day and my pool was using about 1/2 cup of bleach per day - same or less than what others report without the UV unit. So the amount of bleach that a UV unit will burn is negligible in my experience. I changed my UV program to run 4 hours a day a few weeks ago, but now that the sun is out I am up to 1/2 gallon a day...

Nevertheless, I am convinced (having looked at this a lot) that I still need to maintain an appropriate CL/CYA ratio even with the UV.

This!
Even in sunny AZ, I run the pump at 'low' for 4 hours and 'high' for 3 hours at night. So, the UV is sanitizing for 7 hours approx.
Even then, I maintain TC at 5.
In my opinion, maintaining a minimum of 4 FC is required... UV may assist in bringing 'down' the amount of chlorine you need to add to maintain 4 or 5 FC.

 

[jblizzle]

Fair enough that the UV system may not breakdown the FC as much as the sun.

But, are you suggesting that the sun does not put out the same wavelength as the UV system?

I still fail to see the advantage to pay for a system and to run it and then maintain the same FC levels anyway. Even if the UV system did manage to allow you to lower the amount of FC you have to add daily by say 0.5ppm LESS ... those "savings" are never going to counter the cost of the UV system.

... Again I am only talking about outdoor, residential, low-use pools.

 

[marcgr]

The sun puts out all wavelengths of UV. We sort these different wavelengths into bands A, B, and C which have different properties.

UV-A in the 315-480nm wavelength is damaging to chlorine but not particularly damaging to cellular matter.
UV-C in the 180-280nm wavelength is not particularly damaging to chlorine but very damaging to cellular matter.

UV-A is mostly what reaches the earth and gives you a suntan and burns the chlorine in your pool. The UV-B and UV-C is very damaging to cells, UV-B is about 1000x more damaging than UV-A and gives you a sunburn; UV-C is about 5000x more damaging than UV-A. Fortunately UV-B and UV-C is mostly blocked by the ozone layer and very little of it reaches the earth. If the same amount of UV-B and UV-C reached the earth as UV-A, your maximum safe exposure to the sun in a day would be a few seconds. Hence why scientists freak out about the thinning of the ozone layer...

The UV unit puts out UV-C radiation at the 245nm wavelength. Very deadly to cellular matter, but not very harmful to chlorine.