Why are recommended chlorine levels so low when you use pucks/tablets?

Jump to latest Follow Reply
Desiato

Desiato

LifeTime Supporter
May 7, 2015
128
Catalunya, Spain
Pool Size
17900
Surface
Plaster
Chlorine
Liquid Chlorine
I'm almost embarrassed about asking this question because I've been maintaining my pool the TFP way for many years now but I wasn't able to answer this question. I have a CYA level of 50 and keep the chlorine level between 5 and 6 and all has been well (glossing over the PH, TA and CH) but today my wife asked me if I could get a cheap tester just to test the chlorine. I said no because they don't test at levels higher than 5ppm and that reminded me that most websites suggest a chlorine level of between 1 and 3ppm when using chlorine tablets. (like this one Chlorine Level in Pools: What is the Proper Level?).

If I let my FC level drop below 3 my pool will turn green but if I believe these websites and use chlorine tablets it should be fine with a level between 1 and 3? How does that work then?

The other thing that doesn't add up is that if I use chlorine tablets my CYA levels will rise which means I have to raise my chlorine level to suite. So if I switched to using chlorine tablets I would need to keep my FC at 7 then 8 and then 9 as my CYA levels increase. So why do I keep seeing FC levels of between 1 and 3 for tablet use, it doesn't add up, what am I missing?
 
Thanks for the reply's guys. There's actually another reason for asking but I didn't want to go on for too long with the first post. I've been maintaining a friends pool for the last 9 months and been doing it the TFP way and leaving messages for the son in whatsapp about when to add bleach. The problem is he keeps forgetting and after the 10th time (and a clear explanation as to why it is critical you don't miss a top up), I decided I would switch them back to chlorine tablets in spring. I am about to make that switch and that's why the question about chlorine testing came up because I could see I was going to use up a lot of chlorine reagents if I have to keep the FC level high.

The 1 to 3ppm is all over the internet so you would think someone, somewhere (apart from here) would have updated it if it is truly outdated? I even passed by an open door of a commercial swimming pool once and saw they had 1.9ppm written on a chalk board for that mornings test so that also seemed to confirm this "low is the way to go" theory. Still don't get it. :(

The only option I can think off is to backwash regularly as a means of keeping the CYA level down so apart from that, anyone any advice on how best to keep on top of a chlorine tablet maintained pool?
 
You have only one option that will work and that is to monitor cya and drain then refill to keep it within tfp ranges. My brother does this because he does not like to lug jugs for his rather large pool. If I were you I would consider changing to a salt pool. There are a lot of benefits to this approach so many are now switching to salt. I did this after several years of chlorine jug lugging. Will never go back to the traditional chlorine pool using liquid chlorine or pucks. you can read many posts about successful changing to salt. You may also not realize you already have a salt pool. Chlorine addition over time creates salt in your pool. So you probably already have about a thousand parts per million. You will need to increase salt to about 3500 PPM to make into a salt pool. Also, this is only about 10% of salt contained in Ocean salt water. So it is really not very salty at all. Just way way easier to maintain and feels a lot better to most people.

I hope this is helpful.

Chris
 
Thanks aussieta and Chris. I did look into SWGs for my pool many years ago but didn't take the plunge. The most I have to do is one 5l bottle of bleach a day in the summer (chlorine percentages in bleach are lower in Europe than in the US) so pretty easy really, for me anyway. I may have another look at SWGs for myself but for my friend, it looks like regular backwashing and vacuuming to waste will be the answer.
 
  • Like
Reactions: setsailsoon
SWG is the way to go.. If my SWG died today another one would be on order tonight.. Actually mine did die 2 years ago and it was replaced that day...

If you or your friend wants a pool that is easy to take care of then I would really push a SWG... :)
 
  • Like
Reactions: setsailsoon
Desiato said:
I'm almost embarrassed about asking this question because I've been maintaining my pool the TFP way for many years now but I wasn't able to answer this question. I have a CYA level of 50 and keep the chlorine level between 5 and 6 and all has been well (glossing over the PH, TA and CH) but today my wife asked me if I could get a cheap tester just to test the chlorine. I said no because they don't test at levels higher than 5ppm and that reminded me that most websites suggest a chlorine level of between 1 and 3ppm when using chlorine tablets. (like this one Chlorine Level in Pools: What is the Proper Level?).

If I let my FC level drop below 3 my pool will turn green but if I believe these websites and use chlorine tablets it should be fine with a level between 1 and 3? How does that work then?

The other thing that doesn't add up is that if I use chlorine tablets my CYA levels will rise which means I have to raise my chlorine level to suite. So if I switched to using chlorine tablets I would need to keep my FC at 7 then 8 and then 9 as my CYA levels increase. So why do I keep seeing FC levels of between 1 and 3 for tablet use, it doesn't add up, what am I missing?
Click to expand...
1-3 is the industry standard. It's the bare min if you drain and replace some of the water on a weekly, monthly, yearly basis, depending on water quality. The standard comes from the NSPF National Swimming Pool Foundation and Association of Pool & Spa Professionals

The CDC, The Pool Industry, and Sates adopted NSPF. If you want to sell a product for pool and spas you adopt the NSPF standards. If you have a new Item to market you get the NSPF seal or your product sits on the bottom of the shelves.

Water Treatment and Testing | Healthy Swimming | Healthy Water | CDC

www.cdc.gov www.cdc.gov


From the CDC. Pick out the
  • Obtain state or local authority-recommended operator and chemical handling training.
  • Ensure availability of trained operation staff during the weekends when pools are used most.
  • Maintain free chlorine levels continuously between 1–3 parts per million.
  • Maintain the pH level of the water at 7.2–7.8.
  • Test pH and disinfectant levels at least twice per day (hourly when in heavy use).
  • Maintain accurate records of disinfectant/pH measurements and maintenance activities.
  • Maintain filtration and recirculation systems according to manufacturer recommendations.
  • Ensure cleanliness and safety of restrooms, showers, and diaper changing areas.
  • Enforce bather load limits.
  • Scrub pool surfaces to remove any slime layer.
  • Drain and replace portions of the water on a weekly to monthly basis, depending on usage and water quality.
  • Treat the pool with a biocidal shock treatment on a daily to weekly basis, depending on water quality and frequency of water replacement.
  • Institute a preventative maintenance program to replace equipment or parts before they fail (e.g., feed pump tubing, injectors, sensor probes).
  • Provide disinfection guidelines for fecal accidents and body fluid spills.
  • Develop employee policies for staff who are ill with RWIs (e.g., diarrhea) and a communication chain for reporting operation problems.
  • Implement large group orientations, particularly for young children, and bathroom break policies to promote healthy swimming.
  • Educate pool users and parents about RWIs and appropriate pool use (i.e., no swimming when ill with diarrhea).
 

Enjoying this content?

Support TFP with a donation.

Give Support
Thanks for that ferretbone. Interesting that there is no mention of testing Cyanuric Acid levels but they do talk about regularly replacing portions of the water. These two things clearly go hand in hand so why the ambiguity about how to know how much water to replace?

*EDIT*

Looking at the CDC site and this pdf https://www.cdc.gov/healthywater/pd...tor-training-public-comments-and-response.pdf it says:

Comment: 6.1.2.1.1.7 Hyperchlorination - These procedures should also describe what to do when CYA is in the water. Roughly speaking, to achieve the equivalent of 10 ppm FC with no CYA, one needs to raise the FC to be around 10 ppm higher than the CYA level. Because hypochlorite sources of chlorine will raise the pH upon addition (and the pH will mostly drop back down when the chlorine is consumed/used), one should lower the pH first to 7.0. As an example, if one has 4 ppm FC with 20 ppm CYA which is a reasonable amount since that is roughly equivalent to 0.2 ppm FC with no CYA which is sufficient for killing most pathogens and preventing algae growth (it’s around 3 times the level needed to prevent algae growth in residential pools, but is higher for faster kill times in commercial/public pools).

So I'm guessing the 1 - 3ppm guidelines are aimed at people who have very little (say 10ppm) or no CYA in the pool? I can see how this could work in a commercial pool with a constant supply of liquid chlorine but for your average joe who buys chlorine pucks, not a chance!. Anyway, interesting and only confirms what I thought that the 'normal' way to maintain a residential swimming pool is to throw as much stuff in the water and hope for the best.
 
Last edited:
Desiato said:
Thanks for that ferretbone. Interesting that there is no mention of testing Cyanuric Acid levels but they do talk about regularly replacing portions of the water. These two things clearly go hand in hand so why the ambiguity about how to know how much water to replace?

*EDIT*

Looking at the CDC site and this pdf https://www.cdc.gov/healthywater/pd...tor-training-public-comments-and-response.pdf it says:

Comment: 6.1.2.1.1.7 Hyperchlorination - These procedures should also describe what to do when CYA is in the water. Roughly speaking, to achieve the equivalent of 10 ppm FC with no CYA, one needs to raise the FC to be around 10 ppm higher than the CYA level. Because hypochlorite sources of chlorine will raise the pH upon addition (and the pH will mostly drop back down when the chlorine is consumed/used), one should lower the pH first to 7.0. As an example, if one has 4 ppm FC with 20 ppm CYA which is a reasonable amount since that is roughly equivalent to 0.2 ppm FC with no CYA which is sufficient for killing most pathogens and preventing algae growth (it’s around 3 times the level needed to prevent algae growth in residential pools, but is higher for faster kill times in commercial/public pools).

So I'm guessing the 1 - 3ppm guidelines are aimed at people who have very little (say 10ppm) or no CYA in the pool? I can see how this could work in a commercial pool with a constant supply of liquid chlorine but for your average joe who buys chlorine pucks, not a chance!. Anyway, interesting and only confirms what I thought that the 'normal' way to maintain a residential swimming pool is to throw as much stuff in the water and hope for the best.
Click to expand...
If I'm remembering correctly, after extensive lobbying and attempting to educate regulators on the FC/CYA relationship, they conceded by choosing to limit CYA as opposed to increasing the FC limits.

So the allowable CYA limit (for commercial pools) is something like 15ppm. That allowed them to 'acknowledge the relationship' without changing their long-established FC maximum of 4ppm.

Unfortunately, science moves faster than government/politics.
 
  • Like
Reactions: Newdude
magiteck said:
If I'm remembering correctly, after extensive lobbying and attempting to educate regulators on the FC/CYA relationship, they conceded by choosing to limit CYA as opposed to increasing the FC limits.

So the allowable CYA limit (for commercial pools) is something like 15ppm. That allowed them to 'acknowledge the relationship' without changing their long-established FC maximum of 4ppm.

Unfortunately, science moves faster than government/politics.
Click to expand...
Well I guess you may be right on the CYA limits by State. Orenda is lobbying CA and other states to do away with CYA. In Texas the CYA min is over 0, and under 100ppm. Generally speaking.


"Thanks for that ferretbone. Interesting that there is no mention of testing Cyanuric Acid levels but they do talk about regularly replacing portions of the water. These two things clearly go hand in hand so why the ambiguity about how to know how much water to replace?"

You bring up a great point here. Why else I'm I draining my water if the CYA levels are not climbing. There is no mention of CYA on CDC standards. It may be left to some ambiguity because each state or region of the Country the CYA varies in importance do to local year round climates. I know, I know, the sun is everywhere in the US, but rainfall, cloud coverage, etc can different enough to warrant some vage broad spectrum standards Nation wide, and still allow States to tweek those standards in a bit. At least thats how I would want it.
 
Interesting to me is once the CYA/FC and it's impact on disinfecting properties made it past the technologists I started to see articles authored by major CYA producers that described proper us and highlighted this phenomenon. Amazingly to me is that I still think more people in the business don't know about it than do.
 
Follow the money. “Magic potions” generate lots of $$. No need to buy if you follow TFP methods. Most pool stores and pool service company business models rely on pucks and traditional recommendations. The pool service industry would be decimated if everyone followed the science.

On the flip side, websites like TFP have to exist on donations, because no one in the pool industry would advertise on it….cue the ask.

DONATE TO TFP!!
 
  • Like
Reactions: Newdude and setsailsoon
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply