Relationship btw filtering/runtime and chlorine usage

[Johnny B]

A few years ago I posted asking about pump runtime and it was determined that I will get the necessary water turnover per 24 hours just running the pump about 6-8 hours per day, which I split up in two sections.
This year for some reason I seem to be going through a little bit more chlorine than previous summers yet my chemistry remains the same. Specifically I was able to get by with about 30 ounces bleach per day, but now requires about 40 ounces and I saw some algae and so began the shocking procedure.

Perhaps the algae (because it was so small and left untreated, I honestly think it is more of a plaster issue?) was the cause for going through more chlorine and now that I am shocking to eliminate the algae my chlorine usage may return to the lower levels I had in previous summers?

But I was wondering if the thinking is sound regarding: "the more hours the water gets filtered, the less likely you are to run into algae/chlorine issues". I realize that the chlorine chemically goes after the organics, and that filtering is an issue of getting what is possible to be lodged in the filter instead of in your water. So it is sound reasoning to say that the more stuff lodged in your filter instead of being in the water will result in lower chlorine usage? The goal is we want minimal chlorine usage that will get the job done, and we want the least amount runtime that will get the job done. But I'm wondering if I am skimping and should add some runtime?
Thanks

 

[Pool Tool]

I can't comment specifically to your usage, but I do think that while we assume a homogeneous pool water throughout there are localized areas where the FC is higher/lower than others. For example, areas of poor circulation near the corners, walls, etc. So there is some correlation to filter time/algae occurrence, but far and away more important is simply the FC level relative to the CYA level. So many factors at play including plaster, temperature, sun, cover usage, CYA and its testing resolution, etc. generally drive the FC level a touch higher to account for all the variables. You may have had a really good run, maybe your CYA inched up a little and your FC didn't match suit or maybe its just the right conditions for algae. But I think you are right, increased FC usage is the first indicator of algae - well before you see green. Honestly, I couldn't tell you if I used more or less yesterday than the day before so I commend you on your thoroughness.

It will be very interesting to see what your usage does once your Slam is complete and it is a very interesting discussion.

 

[Jimrahbe]

Johnny,

Most pool use 2 to 4 ppm per day. 30 oz of 8.25% bleach will only add 1.0 ppm of FC to your pool. Even 40 oz will only add 1.3 ppm per day.

So I am surprised that you have been algae free this long.

What is your CYA level and what FC level do you normally try to keep.. ?

Thanks,

Jim R.

 

[Johnny B]

Most pool use 2 to 4 ppm per day.
I was unaware of that.
30 oz of 8.25% bleach will only add 1.0 ppm of FC to your pool. Even 40 oz will only add 1.3 ppm per day.
Yes I have determined each summer in the past that my pool was going through one ppm per day and so daily it fell from FC 8 to FC 7 and so I would always bump it back up to FC 8 with 30 ounces bleach. This summer I noticed that I was not so lucky and so began adding 40 ounces, after one week of that still not lucky, hence my post, and maybe as you guys say my luck has dried up and I have to join the 2-4 ppm per day club?




So I am surprised that you have been algae free this long.
Just made another post here, Condition of plaster conducive to algae?
, about this exactly, I thought "crummy plaster issue", maybe I have been wrong all these years, I just assume when you have algae that it is a major problem you absolutely must eliminate or the algae problem will grow. So never having a major algae problem, super easy balancing keeping everything in line, I attributed my "algae" to "crummy plaster". Let me know if I am wrong

What is your CYA level and what FC level do you normally try to keep.. ?
My CYA level has always been best in previous years targeting CYA 50 so that is what I did again this year, and prior to posting this thread I reject the CYA and it is indeed 50. I know CYA 50 is a little high but it has done well for me in the past, but I am thinking that perhaps I need to get back to the 40 range, what do you think

 

[Mr Bruce]

I wouldn't worry too much over it. 50 is fine, just maintain the chlorine above the minimum for 50. If you want to try a lower CYA level, it'll go down slowly over time with rain, splash-out and time.

 

[Jimrahbe]

Jonny,

Each pool is different depending on location and the amount of sun the pool gets.

Yours may indeed only use 1 ppm a day, which would be a great thing. A CYA of 50 will also slow FC usage.

I guess my point is that there is not a lot of difference between using 1 ppm a day and using 1.3 ppm a day..

The key is for you to keep up with what your pool uses and to always maintain an FC appropriate for your CYA..

In your case, with a CYA of 50 your FC should be about 7 and never ever go below 4... See this chart... Pool School - Chlorine / CYA Chart

If you have "some" algae then I suspect you let your FC fall too low.

Thanks,

Jim R.

 

[Johnny B]

If you have "some" algae then I suspect you let your FC fall too low.
That is exactly what I did.
I went to do a 7-10 day FC test & found it 3.5 (expecting 7 or 8!). The 2nd or 3rd time this happened I posted this thread.
hanks to all who helped ! I just have a new "FC use per day" that I will determine & dose accordingly

 

[Johnny B]

If you have "some" algae then I suspect you let your FC fall too low.
That is exactly what I did.
I went to do a 7-10 day FC test & found it 3.5 (expecting 7 or 8!). The 2nd or 3rd time this happened I posted this thread.
hanks to all who helped ! I just have a new "FC use per day" that I will determine & dose accordingly

 

[Johnny B]

Your opinions please.
That little bit of algae is long gone, several days now. I am starting to wonder if I have an ammonia issue? I had an ammonia issue in the past, TFP was great help, it was my very first introduction to pool care believe it or not.

Here is the situation:
- I fail the OClT every night, it seems to fall 3 ppm overnight.
- It seems to fall about 9.5 ppm during the day.

Each evening I get it to shock level, retest in one hour and shock level is reached essentially as expected.
Next morning discover failure of OClT by 3 ppm as mentioned.
In the morning I again raise it to shock level in the morning and maybe add 3 ppm worth more bleach. The evening test later that day reveals a loss of about 9.5 is mentioned and is below shock level. So I'm having a hard time keeping it at shock level (retesting practically every hour ) partly because of the fact that I need to be away from the pool at work etc.

I originally thought that I had some stubborn algae that just wasn't visible, and that be true?

But after several days and intentionally overshooting the shock level and repeatedly failing the OClT + repeatedly falling below shock level after intentionally trying to overshoot it, I'm starting to think ammonia.

If it is ammonia I understand it will take a while and a lot of chlorine. But I forget, is it necessary to really effort to keep it at or above shock level, or it really doesn't matter if it is shock level so long as I keep it in the reasonably high range so that it never comes close to falling below say FC8 or 9?

Is it possible to be needing to maintain "shock level because you have algae" but you simply cannot see any algae?

Final comment: when I look at the pool in the morning I notice some bird poop that is kind of new situation, not gobs of it but present which is a new scenario for my pool. My understanding is that once I finish shocking and maintain the proper FC that it should repel the birds? Perhaps the birds were attracted because of the low FC prior to my shocking?

The next three days should be easier for me to stay on top of it practically hourly if necessary.

Test results
pH maintaining well at 7.7, keeping it in range of 7.5-7.8
FC see above, have been shocking, wondering if I'm having an ammonia issue or I'm just not diligent enough maintaining shock level? During this shocking issue, the lowest it has been is FC 12.5, but as I keep overshooting, about 4 days ago it seems that the lowest was FC 14.5, and most recently for the past 2 days the lowest is FC 15.5. Today's morning test, Thursday, June 15, FC was 19 indicating a loss of 3 ppm overnight and not maintaining a shock level; but as you can see the numbers are improving but still unsatisfactory. Is this an algae issue or an ammonia issue or we don't know or doesn't matter? With a CYA of 50, my shock level is 20, and as I say, upon repeated failures and low FC readings, I intentionally overshoot. Do you guys want me to start targeting a shock of FC 28 or 30? I have been targeting a shock of FC 23 after discovering repeated failures and even then I failed OClTest
CC 0.0 all season including this most recent Shocking issue;
TA 60 on May 5th, time for a retest but I do like to see it go from winter TA 70 towards summer TA 50 range; getting the TA in a specific range has been kind of important over the years to keep my acid demand in line so I stay on top of it, I am about 10 days overdue for a TA test but prefer to test and treat that after this shocking issue is completed unless you guys tell me otherwise and you want me to test a TA now then I will certainly do that.
CH 300 Target (from 275) on April 10; I can retest that if you wish
CYA 50 on June 3rd
borates 0
84° F
CSI: balanced

 

[Pool Tool]

My understanding of ammonia is that you would really never allow you to establish any FC. It eats it almost as fast as you can pour it in.

Sorry to hear of your troubles, but doesn't sound like ammonia.

 

[Johnny B]

Thanks pool tool.
I suppose it is better to have an algae issue than an ammonia issue. I was unaware that you could have an algae issue and see no visible algae.
So the issue is that I simply am not being diligent enough with the shocking process in the sense of maintaining a shock level, correct? As mentioned, the bit difficult being away at work and then expecting a decent result by overshooting after discovering failure at one level so overshoot at the next try (but I still keep failing the tests). Do you guys want me to target FC 28 or 30? Or that is a bad idea, better to retest hourly or maybe a little longer?
I have edited my post #9 above since you commented if that helps you or anyone else.

 

[kcindc]

Overshooting Fc levels wastes bleach and fc loss is greater at higher fc. You will be wasting money. Try adjusting when you get up, right when you get home, after dinner and again before bed. Hit it hard on your days off.

Algae can be present in large quantities and not be visible.

Birds will not go away with higher fc and are at your pool because of low fc.

Brush daily, backwash when your pressure rises 25percent. Look every where for hidden algae skimmer throats behind lights, stairs and letters.

 

[Johnny B]

Algae can be present in large quantities and not be visible.
Great to know thanks.

Birds will not go away with higher fc and are at your pool because of low fc.
You say that birds will not go away at higher FC or is that a typo?

Brush daily,
have been doing that and thanks for saying it
backwash when your pressure rises 25percent.
Did not know that. The pressure has been steady at about 50% greater than minimum, so halfway, so I keep waiting for it to rise so I can backwash but yesterday I decided to backwash anyways before you mention this. Can't believe I did know this, is the issue that "the algae are housed in your filter so you just getting rid of some"?
Is it sound thinking to also be sure that all of your water lines are running? In other words most the time I do not need a pool cleaner when my pool is super clean but in this situation I have that pool cleaner line running just a little bit so I always have highly chlorinated water flowing through it; that's a good idea right?
Also, do you guys like to run the pump 24/7 or that's not really an issue in my case where everything looks super just not getting the test results I'm after at this point.


Look every where for hidden algae skimmer throats behind lights, stairs and letters.
Yes, did that especially the skimmer throat

Overshooting Fc levels wastes bleach and fc loss is greater at higher fc. You will be wasting money.
I did not know that. So you are better off testing about hourly if possible, that I knew, but it seemed to make sense that if I have an algae issue and it requires an FC of 20 that I would be better off not letting it get below 20 (which I have been unsuccessful but that was my thinking )

Try adjusting when you get up,
yes I do that I take it to shock level and lately have been overshooting 3 ppm because I know it will not hold at FC20, as you said yes I have been wasting money
right when you get home, this is what I have just started doing but before today I felt like I could get away with only one test at 1 hour before dark so as to get a second retest in just before dark, today I have done just as you recommended because of my repeated FC readings below my shock of FC 20 (I keep thinking:" if I overshoot even more this time it will hold"

after dinner and again before bed. Got it

Hit it hard on your days off. That is just with what happened the next few days. What do you like, hourly tests, enough to our success will go up to testing every two hours and if successful thing try every three hours,, something along these lines?

Overshooting Fc levels wastes bleach and fc loss is greater at higher fc. You will be wasting money.
I believe you, but are you able to explain that any further for my education.

Thank you very much.

 

[Pool Tool]

If this helps, this is how I rationalize the Slam process. You are basically fighting a "war" with algae. Algae's sole purpose is to reproduce, much like everything else in nature, and unfortunately your nice warm pool is its perfect breeding ground. So along comes you with your jugs of bleach in hand you raise the FC to levels that quickly start to destroy some of the algae. All the while your FC levels are dropping and the algae stop dying as quickly. While the algae has taken a hit, there are still plenty left to continue replicating. This is where the M for Maintaining comes from and why it is so important. You want to prevent the chance for the algae to continue to reproduce and kill the existing, so you raise FC back up to SLAM level and Maintain until the death rate is greater than the reproduction rate. Soon you overcome the algae and take back control. So too sound like a fool, you want to win the war just not the battle.

 

[kcindc]

Backwashing when your filter reaches 25% is about maintaining filtration efficiency. Sand filters work best when a little dirty, but after they reach a 25% increase your water flow is lessened and it is time to backwash. Yes, there can be algae in the filter, but maintaining your FC levels at SLAM level will kill algae no matter where they exist. Again, all about a balancing act. Backwashing too soon means the sand filter won't be able to filter out the finer particles, backwashing too late means that your flow is lessened and you are wasting electricity. Sand filters are great in maintaining a clean pool and are cheap, but they take the longest to clear out dead algae. Cartridge filters are the next step up as in how fast they can clear out a swamp, but have the added cost of replacing the cartridge. DE filters can clear algae the fastest, but are more expensive because you have to add DE after every backwash and some locations do not want DE discharged in yards and/or the sewer system.

Yes, it was a typo... sorry I was typing on my phone right before I went to sleep. The higher FC will not necessary keep the birds away. Your issue isn't birds, it is algae, so don't stress. I have a lot of creatures that drink the water in my pool (bird, bats, bugs, bees, and foxes. I don't have any problems keeping my pool clean... except when a poor creature drowns. I even have a 90+ labrador/otter mix who swims many times a day and drops his dirty rope toys in the pool. Lot of chlorine demand, but not a problem because I keep and maintain adequate FC for my CYA level.

Yes, it is a good idea to keep a little water flowing through your pool cleaner line so it doesn't stagnate and allow algae growth.

There are chemists in this group that helped develop the chlorine/CYA chart and the science behind it that can explain the why does overshooting FC not lead to a better result. From what I know, CYA protects FC, you need enough to keep the sun from burning up the FC. Too much CYA and too little FC leaves too little to keep the organics and algae at bay. Too little CYA and too much FC means the sun will burn the FC and it won't be used to kill organics. The relationship between the two is very important hence why the chart was created.

 

[Johnny B]

Backwashing when your filter reaches 25% is about maintaining filtration efficiency. Sand filters work best when a little dirty, but after they reach a 25% increase your water flow is lessened and it is time to backwash.
Does that apply year round or just during SLAM'ing?

I added DE to my sand filter per Add DE to a Sand Filter
question : After I added the DE (just took 1/2 cup), eventually the pressure rose 25% so I backwashed; do I again add DE in the same 0.25 cup at a time fashion, is the DE gone/backwashed out or is the DE still present?

Your issue isn't birds, it is algae, so don't stress.
OK good to know; FWIW I wasn’t mentioning so much that they were bathing as I was it APPEARS that I'm getting more bird poop in my pool, almost as if there is a new bird flight pattern, or new birds or some disruption of their nearby nesting area; just seemed new. Doesn't matter, it's a chlorine issue no matter the cause or my guesses.


Yes, it is a good idea to keep a little water flowing through your pool cleaner line so it doesn't stagnate and allow algae growth.
This makes sense year round, not just when shocking, right?

Thanks again

 

[kcindc]

Yes back washing when the pressure rises 25percent applies whether you are slaming or not.

Everytime you backwash you loose the de and willl need to add more.

Water through the cleaner line for now when finished slaming using it occasionally should keep it clean.

 

[Swampwoman]

Johnny, I just wanted to add re:

: "the more hours the water gets filtered, the less likely you are to run into algae/chlorine issues"

-I'm a big advocate of moving water personally, and I think where possible one shouldn't skimp on turnover.

BUT thats secondary to ALWAYS maintaining the [fc/cya][/FC/cya] ratio, which is paramount.

Re: slam - how much FC are you losing while away at work? Every minute youre NOT at slam level, you're protracting the slam,which also wastes time and money. With cya of 50 and regular slam of 20, you could afford to dose in am up to 28 before hitting your mustard slam level of 29. In your shoes, if I were losing a lot while at work, I'd be inclined to dose toward, but not over, mustard level to have more hours in the day at/above Slam level. You can get there either way..,I just personally feel this approach is a bit more efficient.

 

[Johnny B]

Monday June 19th
Excellent & Thanks so much.

Re: slam - how much FC are you losing while away at work?
Over the weekend I discovered dosing 40oz per hour was the amount needed to maintain shock level. I hit it hard & successfully Friday-Sunday .But each evening I just go up to FC 21 (hoping tonight is the final night)
Last night I lost 3ppm
Today Monday before I left for work I targeted 5 hours x 40oz per hours = 200oz 8.25% bleach hoping I'd be at FC 20 5 hours hence. Nope, FC 14.5, not even close (but it was likely 6hrs not 5 hours but still not close). When I added this 200oz , I was at FC 20 or 21 because I was able to do two doses 1 hour apart prior to this 200oz dose. 30 oz will raise it 1ppm so 6.67ppm, say 6ppm & say I was at FC 20 means I reached FC 26, yet 6 hours later it tests FC 14.5.

I never had to shock much over the years & when I did it was quick (except one ammonia issue). This has me spooked, but of course if I can't keep it at SLAM level then of course as you say it prolongs it. You guys don’t think I have mustard algae at this point do you? I will be able to hit it ideally tonight & on Tue & Wed. Thursday will be a work day, & you want me to Target 28 or something higher based on the info I provided in this post

Every minute you're NOT at slam level, you're protracting the slam, which also wastes time and money. With cya of 50 and regular slam of 20, you could afford to dose in am up to 28 before hitting your mustard slam level of 29. In your shoes, if I were losing a lot while at work, I'd be inclined to dose toward, but not over, mustard level to have more hours in the day at/above Slam level. You can get there either way..,I just personally feel this approach is a bit more efficient.

That is exactly what I will do & concluded that "if I fail my Monday workday plan I'm going to ask you guys about raising the dose level, you still like Target28 ?

 

[Johnny B]

Hoping to get a few comments from the pros.
Last night 10:30 pm test FC24 so targeted FC28
Today Tue am OClTest FC 25 so still falling 3ppm overnight.
What FC do you guys want me to target:
1- daytime when I can dose hourly? ___
2- daytime when I'm away & cannot dose hourly? ___
3- overnight ? ____
To save you fr reading: my SLAM level is FC20 & a pro mentionedthat my (black/mustard?) algae level is FC29
Thanks