Chlorine level for low and high water temp

[FIESTA62]

hi, i think i have my pool water balanced pretty good at this point with all the help from you guys but wanted to confirm what i read in a pool book put out by a pool chemical guru, Bernie Skelton 30 year pool guy.... my main question here is he says

Chlorine set at 1.5 if below 26 Celsius /79 F or set at 3 if above 26 Celsius / 79F .....

i see on pool math it depends on CYA level, my CYA is 25 to 30 and pool math says set FC to 4, but at this point my pool temp is only 16 Celsius / 60F, so if i follow pool guru i would be setting at 1.5 but if i follow pool math i set at 4 , big difference

i can lower CYA to be able to lower FC level needed but i understand CYA is best kept between 30 to 50 and i think mine is around 30 now

so do i just follow the rule this pool guru says.....or follow the level pool math says depending on CYA level .....so many various opinions i read very confusing, thanks

 

[CRAD_oz]

Experts can explain in more depth but in short
The TFP way is going to be different to what others may say. Try not to mix other methods and the TFP way. You'll end up spinning around and confused.

 

[FIESTA62]

Experts can explain in more depth but in short
The TFP way is going to be different to what others may say. Try not to mix other methods and the TFP way. You'll end up spinning around and confused.

ok but i am wondering are these rues set in stone, like do i follow TFP rule regardless of temp, or be flexible and listen to others, like now pool math says FC should be 4, with my cya at 30, but FC 4 seems high for this time of year and pool temp only 16, i am thinking obviously it would be easier if i just follow pool math on my phone and forget the rest....which i will be doing at this point

 

[CRAD_oz]

An FC of 3 with 0 cya is more harsh than having an FC of 4 with 30 cya I believe. With temperatures rising slightly, Spring in the air and the rain showers lately I would want to keep it on the high side of the target FC.


My pool is only 14deg C now. Do you get a lot of sun on your pool?

 

[FIESTA62]

An FC of 3 with 0 cya is more harsh than having an FC of 4 with 30 cya I believe. With temperatures rising slightly, Spring in the air and the rain showers lately I would want to keep it on the high side of the target FC.


My pool is only 14deg C now. Do you get a lot of sun on your pool?

i face south east pool gets sun around half the day... my pool is FC 1.8 level now, i thought that was enough going by the book i read that says under 26 Celsius FC should be 1.5......but thats not what pool math says

 

[mgtfp]

Algae reproduction rates may be slower with colder water, but CYA actually binds more chlorine at lower temperatures, i.e. less "active" chlorine (HOCl) at lower temperatures. These effects kind of compensate each other, i.e. best to just keep FC constant. In a pool without CYA, it goes the other way round, colder water means more HOCl at constant FC levels - most in the industry haven't really bothered to understand the CYA chemistry.

And spring has started, you just need a few warm days to get your water temperatures up. I wouldn't risk an algae bloom with your brand new pool, and with 16°C your water is not that cold anymore (I'm still at 12°C here in Melbourne - up from 8°C in winter...).

 

[FIESTA62]

ok so i need to get the FC up to 4 as pool math says...... i tested the cya a few times and could always see the black dot, i kept adding more stabilizer a bit at a time, bunnings as u suggested, tested 2 days ago and at 30 the black dot was very feint i could still see it holding at waist level , but it was very faint so i guess that's 30 or say 25 to 30,
so assuming its 30 then pool math says FC needs to be 4, pool is at 1.8 now, i will put some chlorine in tomorrow, i have not added salt to the pool yet

 

[mgtfp]

As long as there is CYA in the pool, you don't really have to worry about having too much chlorine in the pool. That's why we encouraged you to add CYA as quickly as possible after you filled your pool (apart from protecting your chlorine from UV). Once temperatures and UV intensity get higher, you can start adding more CYA, but there is no rush as long as you don't have problems maintaining your FC. And by doing it step wise you can keep practicing the CYA test on the way, and avoid putting too much in.

I like this post from Chem Geek where he puts chlorine levels in pools with and without CYA into perspective:

I don't have actual data on that, but anecdotal evidence supported by chemical theory. My wife swims in an indoor commercial pool over the winter 3-4 times a week that has had 1-2 ppm FC with no CYA in the water and every winter season her swimsuits get worn out where the elastic gets shot and the fabric gets thinner, basically having her need to get new swimsuits for each winter season. In our own outdoor pool with 3-6 ppm FC and 30-40 ppm CYA, her swimsuits have lasted for 9 summer swim seasons swimming almost every day though she now says she is starting to notice wear. The difference in active chlorine level between the two pools is roughly a factor of 10-20 which likely is reason for the difference. The same is true for the flakiness of her skin and frizziness of her hair between the two pools.

Obviously the answer will depend on the actual fabric of the swimsuit and frequency of use, but I'd say that roughly speaking 40 expsoure-hours in 1-2 ppm FC with no CYA is probably when the swimsuit gets too worn out (assuming she was rotating between at least a couple of swimsuits). Remember also that there is physical deterioration from wearing the suit and swimming, not just from chlorine exposure, but the difference in experiences between the two pools shows that the chlorine difference is the major factor. In our own pool with an FC that is around 10% of the CYA level the swimsuits are lasting around 900 exposure-hours or so which is somewhat better than what the chemistry would predict.

A shock level of chlorine where the FC is around 40% of the CYA level is equivalent to 0.6 ppm FC with no CYA so a swimsuit would last around 70-130 hours while at yellow/mustard algae shock level where the FC is around 60% of the CYA level and is equivalent to 1.5 ppm FC with no CYA so would last around 40 hours and be roughly similar to an indoor pool that didn't use CYA.

Note that there is another factor that is dependent on the FC level alone and not on the active chlorine level. Namely, it is the chlorine capacity or reserve to continue to react with the swimsuit after one gets out of the water and such water evaporates. In this situation, a higher FC can lead to more swimsuit wear unless one rinses their swimsuit after they get out of the pool. My wife would normally do that with her suits except on weekends when we would both be using the pool and hang out in the sun after swimming.

Chem Geek used to be very active on TFP, there are some good sticky threads in the deep end that are worth a read if you are interested in understanding the scientific background of the TFP method.

 

[FIESTA62]

ok i did all tests today and for the first time actually got the CYA test to the point where i don't see that black dot, i did test 1 week ago after adding stabilizer and i got 30....i did wait 3 days after adding stabilizer before testing,

then i test again today 1 week after last test at 30 and i cant see black dot now at 50, i can very faintly see at 60, so i guess CYA is 55, strange how it tested to CYA 30, 1 week ago but now i get 55, i tipped test out and refilled again to check its spot on around 55

so with 55 CYA the pool math says FC 6, my pool FC is 1.4, so i am way off, so i added the recommended 1.3 litres of chlorine to target FC 6

TA 80 PH 7.6 Temp 15c / 60 F

CH was 200 so i added 2kg of calcium up to target CH 250, im not sure of best target just going for 250

i did CSI although i dont really understand it and CSI is -0.45

apart from all this pool is sparkling so i must be doing something right ! but please sort my NCPM (no clue pool method) out if im messing up....

 

[Dirk]

@kimkats, why is it always 30 years?!? Always! It's a running joke she and I have. Whenever someone needs to bolster their credibility by conveying their expertise using years in the biz, it's always 30. Always. All that says to me now, after some direct experience with this phenomenon, is that they haven't bothered to learn anything for 30 years! Those FC recommendations of his might be at least that old.

The others here are giving you great advice. I'll reiterate: mixing and matching advice from multiple sources, like pool store, pool guy, neighbor, TFP or Bernie, or your own ideas, etc. will ultimately fail. No matter how logical it sounds. TFP offers a virtually foolproof method of pool care. You might get several of us here offering advice, but it will all be from the same rule book. It's also one of the most cost effective methods. It's yours, free, for the taking. It will work, if you follow the instructions carefully. And that notion is backed by a hundreds of thousands of folks that have had success with it. If it feels better to try another's method, then only use his, and don't mingle in our advice with his, or his advice will fail. I'm a little late to this party, so if you've already decided to go with TFP, and only TFP, then, well... nevermind!

 

[FIESTA62]

@kimkats, why is it always 30 years?!? Always! It's a running joke she and I have. Whenever someone needs to bolster their credibility by conveying their expertise using years in the biz, it's always 30. Always. All that says to me now, after some direct experience with this phenomenon, is that they haven't bothered to learn anything for 30 years! Those FC recommendations of his might be at least that old.

The others here are giving you great advice. I'll reiterate: mixing and matching advice from multiple sources, like pool store, pool guy, neighbor, TFP or Bernie, or your own ideas, etc. will ultimately fail. No matter how logical it sounds. TFP offers a virtually foolproof method of pool care. You might get several of us here offering advice, but it will all be from the same rule book. It's also one of the most cost effective methods. It's yours, free, for the taking. It will work, if you follow the instructions carefully. And that notion is backed by a hundreds of thousands of folks that have had success with it. If it feels better to try another's method, then only use his, and don't mingle in our advice with his, or his advice will fail. I'm a little late to this party, so if you've already decided to go with TFP, and only TFP, then, well... nevermind!

yep as most last post i am doing what the pool math says heading for the FC6, the highest my pool FC has been since start up is 1.8....but i will work it and follow TFP

 

[Jeff J.]

ok i did all tests today and for the first time actually got the CYA test to the point where i don't see that black dot, i did test 1 week ago after adding stabilizer and i got 30....i did wait 3 days after adding stabilizer before testing,

then i test again today 1 week after last test at 30 and i cant see black dot now at 50, i can very faintly see at 60, so i guess CYA is 55, strange how it tested to CYA 30, 1 week ago but now i get 55, i tipped test out and refilled again to check its spot on around 55

so with 55 CYA the pool math says FC 6, my pool FC is 1.4, so i am way off, so i added the recommended 1.3 litres of chlorine to target FC 6

TA 80 PH 7.6 Temp 15c / 60 F

CH was 200 so i added 2kg of calcium up to target CH 250, im not sure of best target just going for 250

i did CSI although i dont really understand it and CSI is -0.45

apart from all this pool is sparkling so i must be doing something right ! but please sort my NCPM (no clue pool method) out if im messing up....

You always round up to the next ten. So there is no 55, it's 60.

 

[mgtfp]

You have the advantage that you know exactly how much CYA has been added up to now, according to your PoolMath logs 1780g, that should result pretty much in about 50ppm in your 36k litre pool. If you had a lot of evaporation, it might be more, if you had lots of rain it might be less.

Most here go with the following for the CYA measurement:
Fill to a line and have a quick glance. If you can see the dot, fill to the next line. If you can see the dot, then fill to the next line. Repeat until you can't see the dot with a quick glance - that's your reading.

In your case you saw the dot at 60, but not at 50 - your reading is 50. Don't bother with inbetween values, the tube has a logarithmic scale.

And that reading matched perfectly what you have added so far. Remember how that dot was still just visible at 60 and disappeared at 50. Since you know exactly what you've added, your pool is now a nice reference sample.

CYA can take a couple of days to dissolve, maybe some got parked in the filter, will take a bit longer to dissolve there.

 

[FIESTA62]

You always round up to the next ten. So there is no 55, it's 60.

ok will do thank you....

 

[kimkats]

LOL yeah it is "I have been doing xxx for 30 yrs".................

TFP ways are backed by science. I can share the scientific papers with you if you want. The 30 yr guy is going by the old thinking of not having fc higher than 2. Once the use of CYA was started that all changed. The CYA buffers the FC so you can and should push the FC higher to keep algae away and your pool clear and sanitized. SLOWLY the the pool world is starting to listen to and understand the ratio of CYA/FC.

 

[FIESTA62]

LOL yeah it is "I have been doing xxx for 30 yrs".................

TFP ways are backed by science. I can share the scientific papers with you if you want. The 30 yr guy is going by the old thinking of not having fc higher than 2. Once the use of CYA was started that all changed. The CYA buffers the FC so you can and should push the FC higher to keep algae away and your pool clear and sanitized. SLOWLY the the pool world is starting to listen to and understand the ratio of CYA/FC.

no need to show me science I'm a car guy guitar player we don't do science ! and it would not make a lot of sense me reading it, i will follow TFP, the book i refer to is on the counter at probably our biggest pool outlet shop here in Sydney so i grabbed a copy and just had to ask u guys about his method, but as Dirk said i got to follow one way and stick to it and from all the advice i have been given so far from all the TFP members i cant fault, so im with you guys....

 

[FIESTA62]

You have the advantage that you know exactly how much CYA has been added up to now, according to your PoolMath logs 1780g

hi, actually i just checked my book, i write down what i been doing, i have put 2.8 kg CYA in, i must have missed recording it into pool math i just updated that, but as said the dot was gone at cya 50 so thats it....

i checked FC again today after adding the 1.3 litres yesterday and pool is now FC 3.6 highest ever.....i added another litre today aiming for the FC 6 as pool math recommends.

how long does the CYA keep it level at say the 50 i have now, is it a weekly/monthly, or longer between top up with stabilizer ? just wondering how often i should be checking...

 

[FIESTA62]

i did my calc on the 2.8kg of stabilizer i added to my 36000 litre pool, if i am right cya level would be close to 80, i got 50 in test, ( 60 faint dot / 50 dot gone ) i was looking to get 50.......not 80...... i will test cya again tomorrow just to be sure....

 

[mgtfp]

Yep, that should be close to 80. Did you vacuum your pool not too long after adding CYA, either to waste, or to filter and then backwashed? In that case, there might have been some undissolved CYA left that never got a chance to dissolve before it went down the drain...

CYA doesn't have to get topped up very often, what's in, mainly stays in. It remains in the pool when water evaporates, so once you topped up evaporated water from the tap or with rain, you're back to where it started.

You lose it by rain overflow (that removes the CYA with the water) or water losses by splashing. And of course by backwashing the filter or by vacuuming straight to waste. Of course, that doesn't change the ppm directly, but eventually you will replace the lost water with water that doesn't contain CYA, and the CYA that's remaining in the pool gets diluted.

There is also a small constant loss by chlorine (and by radicals that get created by UV breaking down active chlorine) oxidising CYA, particularly at higher water temperatures and higher UV-loads. That can lead to CYA losses between 2-10ppm per month (particularly in hot desert climates).

Once you are dialed in, it's usually enough to test CYA monthly and top up as required.

Don't add anymore for now. When you have the SWG running and it gets warmer you can add more to get to the SWG target range. But you don't want to overshoot. CYA above 80 is maintainable as long as everything is fine, but the problems start when you do get algae, the required very high SLAM levels are difficult to maintain.

Run another test tomorrow to double check where you are. But with the additions that have been done, I'd rather assume 60 than 50 for now so you don't under-chlorinate and to avoid overshooting later on.

The "Further Reading" article on CYA is quite good, has a few more details and links:

CYA - Further Reading

www.troublefreepool.com

 

[FIESTA62]

Did you vacuum your pool not too long after adding CYA, either to waste, or to filter and then backwashed?

i remember reading not to backwash after adding cya for days so I'm sure i didn't, i have only vacuumed twice since start-up but cant say for sure if i vacuumed close to the cya going in.....cant remember but i doubt it.

i will test again tomorrow, i put the test bottle on the pool coping so its steady not shaking water , my previous tests i learnt just holding it the water moves and makes the dot less easy to see or not see, so i set it down and kneel over it back to sun,

one tfp member mentioned cya test water should be room temp, my test yesterday was like 15c so not room temp, could that have made a big difference in results ?