I have read in several places online that it is important to maintain a minimum three ppm free chlorine in order to prevent algae. However, I recently typed "30 ppm of CYA" into your chlorine calculator and it recommended a minimum of 2 ppm free chlorine. Why would you guys recommend less than the minimum amount needed to prevent algae? Thanks in advance.
Contradictory Information
- Thread starter KevinL
- Start date
- Jul 17, 2019
- 3,721
- Pool Size
- 13000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
You will find several differences in TFP recommendations and conventional pool "wisdom". TFP is based on science and ignores many of the old ways of thinking. This is most evident in the Chlorine recommendations. Here at TFP we treat your Free Chlorine requirement as a variable based on CYA. Pool stores and much of the pool industry is based on the science before CYA was added to pools and will typically have a static FC recommendation (FC of 1-3, or something similar).
For the most part, TFP will recommend much more chlorine than what you get at the pool store and other publications. Read more about the FC/CYA relationship here, including why it differs from conventional numbers.
www.troublefreepool.com
For the most part, TFP will recommend much more chlorine than what you get at the pool store and other publications. Read more about the FC/CYA relationship here, including why it differs from conventional numbers.
The Free Chlorine and Cyanuric Acid Relationship
Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.
www.troublefreepool.com
Recommendations vary also based on how your oxidizer (usually chlorine) is being added. 2ppm is generally fine if you don't have a very high CYA level AND are constantly testing and adding chlorine as needed, or if you have a constant source of new chlorine to replace what is being consumed (such as a salt water generator).
However, this level of chlorine can very quickly be consumed by things such as rain, high bather load, junk getting blown into the water, etc., and if that happens it gives algae a chance to grow. After such events it's a good idea to raise the level of chlorine to the appropriate level so that it can oxidize anything that was introduced to the water before it has a chance to gain a foothold.
However, this level of chlorine can very quickly be consumed by things such as rain, high bather load, junk getting blown into the water, etc., and if that happens it gives algae a chance to grow. After such events it's a good idea to raise the level of chlorine to the appropriate level so that it can oxidize anything that was introduced to the water before it has a chance to gain a foothold.
Kevin,
There is a lot of difference between the 'Minimum' and your target FC.. You should not be trying to keep your FC between the minimum and your target. You try to always keep your FC at or above your target.
With a CYA of 30 the minimum may be 2, but your FC should be kept between 4 to 6 ppm.
Thanks,
Jim R.
There is a lot of difference between the 'Minimum' and your target FC.. You should not be trying to keep your FC between the minimum and your target. You try to always keep your FC at or above your target.
With a CYA of 30 the minimum may be 2, but your FC should be kept between 4 to 6 ppm.
Thanks,
Jim R.
The 2 is there in case you have a "oh my" situation where you forgot about the pool so if when you return it would be a sigh of relief sort-of that it's still the minimum but for the usual pool care you go by the target and the higher side of target is even better.
Thank you, Jim, that's very interesting. During the summer I find that I have to add chlorine every day because I lose about 4.5 ppm daily due to the sunshine and heat of the summer.
So this means every evening I need to get my chlorine up to 8.5 ppm to ensure I don't go below 4.0 ppm during the next 24 hours?
(PS - yes, I did the overnight chlorine loss test, and it showed I lost 0.8 ppm)
Thanks in advance, Kevin
Winner Winner Chicken Dinner !!!!!
You need to dose daily :
Minimum FC per your CYA. +
Recent daily loss +
1 or 2 ppm wiggle room
-------‐-------------------------
= Trouble Free Pool.
Lots can happen with that wiggle room. A big storm, a particularly high UV day, an impromptu get together..... it will save you again and again and you won't even know.
I like your equation, New. But it seems to contradict Jimrahbe above who said, "You should not be trying to keep your FC between the minimum and your target. You try to always keep your FC at or above your target."
It's more or less the same. If you added 2ppm wiggle room to your minimum, you'd be at low target, and low target would effectively be your 'minimum' and as close to minimum FC as you ever came.
Funny you should mention it as I'm a big fan of 'running hot'. It's extra and not necessary to add even more than that, but it affords you some leeway to not pay so close attention to it.
Also, as it's the peak season, we are all losing our most daily loss right now. As the season winds down, you can lower the daily dose accordingly. For example, when you're losing 2ppm a day in a couple months, there's simply no need to aim so high.
It's a moving target.
Okay thank you. I understand that you like to keep a slightly higher ppm of chlorine, and that's what you meant by running hot. Do you worry about swimmers being affected by too much free chlorine?
- Jul 17, 2019
- 3,721
- Pool Size
- 13000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
I like to run hot and nobody has been affected by the high chlorine yet. Heck, the high chlorine even took care of my son's extra hand he grew after the last swim season.
Seriously though, you should see no issue with swimmer comfort with FC levels up to the SLAM level. Note that if you maintain your chlorine in the recommended range (or higher) your pool is able to easily handle any contaminates.
A lot of the fear of chlorine is really Combined Chlorine (CC), which causes the chlorine smell and irritates the eyes. CC is created when your chlorine is attacking something (algae/other contaminants). If you let your chlorine get too low, then suddenly add some chlorine it will have lots of contaminants to fight and therefore a higher CC. By maintaining the chlorine at the recommended level, it can fight contaminants near real time and before those contaminants get worse/multiply, and therefore you will have a lower CC and greater swimmer comfort.
My MIL is convinced that my pool doesnt have very high chlorine since it doesnt bother her skin like her pool at home. I've stopped trying to explain that my pool has 3x the amount of chlorine in it than hers.
None whatsoever. SLAM FC (40% of your CYA level) is less harsh than tap water with 0 CYA and up to 4ppm FC. I aimed for SLAM a few weeks back expecting 25 swimmers at a blowout party. I fell a bit short and they swam for hours at 20 FC. (SLAM being 28 FC for my 70 CYA). Nobody but me had a clue.
Lifted from Pool School :
Free chlorine is an aggregate value of three distinct forms of chlorine -
FC = [HCy-Cl] + [HOCl] + [OCl-] Free chlorine = "chlorine bound to CYA" + Hypochlorous acid + Hypochlorite anion[2]
When CYA is present in pool water above 30ppm or so, almost 95% of the chlorine in the water is bound to the CYA molecule where it is not reacting with anything. The test of the chlorine splits up into hypochlorous acid (HOCl) and hypochlorite anion (OCl-). Those two chlorine species are often called "active chlorine" as they are the chemical agents responsible for oxidation and disinfection. HOCl is what kills algae & bacteria and inactivates viruses, and it is also responsible for the oxidation of organic compounds. Hypochlorite anion is a weak oxidizer and disinfectant but sit strongly reacts with UV light and is reduced to oxygen gas and chloride ion (Cl-). As the HOCl and OCl- get used up, more chlorine is released from the CYA to maintain an equilibrium balance. So chlorine bound to CYA is often referred to as "reserve chlorine". So in this way, CYA acts as a buffer for chlorine's reactive species.
Because of the chemistry involved, the DPD dye reacts to all three forms of "active chlorine" and so you are measuring an aggregate value. There is no way to measure the three species separately outside of a very sophisticated chemistry lab, so the simpler value of FC is what is used.
Active chlorine levels are different than Free Chlorine levels. As long as your FC/CYA ratio is between 5% and 40%, the water is safe to swim in from a chlorine perspective. Considering the FC/CYA ratio is important because we do not have a direct way of measuring the Active chlorine.
Free chlorine is an aggregate value of three distinct forms of chlorine -
FC = [HCy-Cl] + [HOCl] + [OCl-] Free chlorine = "chlorine bound to CYA" + Hypochlorous acid + Hypochlorite anion[2]
When CYA is present in pool water above 30ppm or so, almost 95% of the chlorine in the water is bound to the CYA molecule where it is not reacting with anything. The test of the chlorine splits up into hypochlorous acid (HOCl) and hypochlorite anion (OCl-). Those two chlorine species are often called "active chlorine" as they are the chemical agents responsible for oxidation and disinfection. HOCl is what kills algae & bacteria and inactivates viruses, and it is also responsible for the oxidation of organic compounds. Hypochlorite anion is a weak oxidizer and disinfectant but sit strongly reacts with UV light and is reduced to oxygen gas and chloride ion (Cl-). As the HOCl and OCl- get used up, more chlorine is released from the CYA to maintain an equilibrium balance. So chlorine bound to CYA is often referred to as "reserve chlorine". So in this way, CYA acts as a buffer for chlorine's reactive species.
Because of the chemistry involved, the DPD dye reacts to all three forms of "active chlorine" and so you are measuring an aggregate value. There is no way to measure the three species separately outside of a very sophisticated chemistry lab, so the simpler value of FC is what is used.
Why Do Others Warn About Chlorine Levels That TFP Recommends?
The problem is, the "harshness of chlorine" depends on the HOCl level mostly and so basing recommendations on FC without considering CYA is illogical and why the industry has such a poor track record at helping people maintain clean and clear swimming pools.Active chlorine levels are different than Free Chlorine levels. As long as your FC/CYA ratio is between 5% and 40%, the water is safe to swim in from a chlorine perspective. Considering the FC/CYA ratio is important because we do not have a direct way of measuring the Active chlorine.