Safe Free Chlorine Levels for swimming?
- Thread starter newfool
- Start date
Depends on your CYA level. See the Chlorine / CYA chart in Pool School. Anything from the minimum to shock level is alright for swimming, assuming the water is clear and no problems elsewhere.
I've read the chart and used the calculator. I ask because I read somewhere that the recommended max safe swim levels of free chlorine was 4 - this was taken from a website regarding commercial pools. Does anyone else have an established safe max FC level with documentation?
Might want to see what they say as max levels for CYA in commercial pools, maybe that will help.
Can you provide a link to the website that has this information? I would like to see this for myself. No offense but I have read so much ******** from every huckster on the planet that thinks they are the authority on pool care. I have never read anywhere that an FC level of 4 is a limit on the maximum FC level for a safe pool. Personally, I believe a pool anywhere under 8 is a pool I would swim in. Anything higher and my only worry is bleaching out my swim trunks.
Many commercial pools do not use cya. In terms of active chlorine (HOCL) levels, a pool with 4 ppm FC and 0 ppm cya has a disinfecting (or active) chlorine level of ~ 1ppm HOCL. To get that same active chlorine level (1 ppm HOCL), you would need ~ 40 ppm FC at 50 ppm cya (the recommend cya level from troublefreepool). There is much more on disinfecting chlorine verses FC levels at varying cya levels in chem geek's excellent post here: http://www.troublefreepool.com/pool-water-chemistry-t628.html
That document is really focused on warning about FC levels being to low not high. With that said, they did say this:
So they definitely leave the door open to allowing higher FC levels, and even hint, by including cya levels, that it might be appropriate to be higher.
Agreed, I just wonder if there is a high side limit. I have always erred on the side of too low and it makes it too difficult to chase the chems with my work schedule. I don't want to be exposed to too much chlorine either...
The EPA limit is 4 ppm, but that is based on drinking water standards. Nevertheless, it carries over to FIFRA rules for chlorine product labeling so you will never see a pool chlorine product say to dose higher than 4 ppm for normal levels when a pool is in use (you can see 5 ppm for spas). However, commercial/public pools are not regulated by the EPA, but by state and county (and sometimes city) regulations. See this post for a variety of regulations showing maximum chlorine levels from 3 to 10. However, none of the regulations reflect any understanding of the chlorine/CYA relationship, though the regs that allow up to 10 are intended for outdoor pools that presumably have CYA in them.
The fact is that pools with CYA have so much lower active chlorine levels that comparing them to pools without CYA with respect to "safety" in terms of oxidation rates of swimsuits skin and hair is ludicrous. The only relevance to the FC level when there is CYA is if you were to drink voluminous quantities of water. Remember that the EPA 4 ppm limit assumes drinking 2 quarts (liters) of water every day for a lifetime for a lifetime cancer risk from regulated chlorinated disinfection by-products of less than 1 in 1 million.
The fact is that pools with CYA have so much lower active chlorine levels that comparing them to pools without CYA with respect to "safety" in terms of oxidation rates of swimsuits skin and hair is ludicrous. The only relevance to the FC level when there is CYA is if you were to drink voluminous quantities of water. Remember that the EPA 4 ppm limit assumes drinking 2 quarts (liters) of water every day for a lifetime for a lifetime cancer risk from regulated chlorinated disinfection by-products of less than 1 in 1 million.
Thanks chem, this is why I have been having some issues here and there. My target was to stay at 4-10 max, but realistically with my work schedule, it was more like raise it up to 10 and then it would come down to 0-2 before I was able to service again...
My CYA level's typically range between 25-40. I tend to keep them low so that shocking is easier, late season, say late july-august I sometimes get mustard algae or the beginnings of such. It's only may and I notice some yellowing at the bottom of the pool!
Pool temp 81, sunny high of 90, dry, cya 35, FC2, pH 7.6, alk 70, hardness 260.
The current issues I am having aside from the yellowing in areas of the bottom of the pool is clarity - this is the first time in years that I am seeing a dullness/slight opacity looking through the water. I have been thinking about using some DE. Is there something better? The cartridge filter has just been cleaned, but is 2 years old.
Sorry for the late response!
Pool temp 81, sunny high of 90, dry, cya 35, FC2, pH 7.6, alk 70, hardness 260.
The current issues I am having aside from the yellowing in areas of the bottom of the pool is clarity - this is the first time in years that I am seeing a dullness/slight opacity looking through the water. I have been thinking about using some DE. Is there something better? The cartridge filter has just been cleaned, but is 2 years old.
Sorry for the late response!
Your FC level is below the recommended minimum, and that certainly has something to do with your problem. A dull water appearance is often the first visible sign that FC has fallen too low. Keeping CYA low actually increases the odds of getting algae, and requires more total chlorine besides.
If you maintained appropriate FC levels you would not be having algae problems.
If you maintained appropriate FC levels you would not be having algae problems.
But adding more CYA will make it harder to shock, what CYA concentration do you recommend for my pool? Yesterday I took up my chlorine levels by adding 2.5g of liquid chlorine, by pool calculator's estimates that should be a FC of about 23.5
If your CYA is 35 then your FC target range is 3-7 and a slam level of 14. You should shoot for keeping the FC at 7 and never let it drop below 3.
We often advise pool owners that it's fine to swim all the way up to shock level. You could err on the side of caution regarding the margin of error on the CYA test and assume your CYA is really only 25. This would put your shock level at FC 10.
Good point gents, thanks. I often do let the chlorine run out, that has been my problem... There are some times where I wont be back home for 2-3 day stretches. I try not to use pucks because they mess up the cya balance too much.
So where ya been? It is like this thread got in a time warp and continued where it left off 14 months ago :lol:
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