What is consuming chlorine?!? SWCG can't keep up. Been SLAMing. Crystal clear pool now. Never algae on walls .

[TaylorN]

UV and/organics consumes chlorine. You have a covered pool the majority of the time. So that leaves organics. SWG are designed to keep up with a set FC level, when utilizing the FC/CYA chart. Per this thread you've set your SWG + pump run time = FC 3.2 ppm

With your climate in San Diego a FC loss of 3.2 this time of year would be acceptable. Since your post doesn't show testing everyday, it is difficult to really understand your FC losses. Because your pool is covered the majority of the time, you feel the FC should keep rising because the sun (UV) isn't burning off the chlorine. Which leave organics.

You really need to perform an OCLT. With your cover open all night, test your FC level after dark and before sunrise. (yes, set an alarm and test before the sun comes up). I believe I read in this thread you did an OCLT and had a loss of FC greater than 1 ppm. Which means you have organics.



Those were my thoughts. I have an autocover and I still keep my CYA in the recommended value range around 70 ppm. However, I open my cover most days between 12 pm to 6 pm. I am part of the #FCrunhot crew and keep FC around 8 - 10. Swim parties or not, FC has never dropped below minimum, that is why I have a SWG. Oh, btw, today mine is set for 24/7 33% which yields 3.0 ppm.

Excellent info Brad!

So I didn't fill in the every day numbers recently because at this point it is pretty much stable at 18fC daily since we aren't using the pool.

And you are saying if I am generating 3.2ppm per day and also losing/being-consumed 3.2ppm per day, then that is about normal for peak summer? So maybe I am not actually off then after all.

With the CYA of 35, running around 6fC should be fine if I can keep that stable with 3.2ppm generation per day. Ultimately I like what you are doing with 70 CYA and fC around 8-10. I will shoot for that in the coming weeks after I do the OCLT and drop the FC down .

Just to clarify when you say a FC loss of 3.2, do you mean throughout the daylight, or over 24 hours? I assume over 24hours

 

[an1vrsy]

Just to clarify when you say a FC loss of 3.2, do you mean throughout the daylight, or over 24 hours? I assume over 24hours

UV and/or organics consume chlorine. There is no UV loss at night. It is only during daylight hours when your pool gets direct sun. Keep in mind, that is why you are going to perform an OCLT. No chlorine burn off overnight or rather that is what you'll be testing for.

 

[Kilkennyeddie]

Have you checked for high Phosphates ? I had aa similar problem and that what it turned out to be.

 

[Bperry]

Have you checked for high Phosphates ? I had aa similar problem and that what it turned out to be.

Phosphates don’t matter if there’s adequate chlorine.

 

[TaylorN]

UV and/or organics consume chlorine. There is no UV loss at night. It is only during daylight hours when your pool gets direct sun. Keep in mind, that is why you are going to perform an OCLT. No chlorine burn off overnight or rather that is what you'll be testing for.

Ok. so if the cover stays closed all day (no UV loss from daylight) and we are losing ~3ppm fC everyday and generating ~3ppm fC everyday, then its simply the organics causing Chlorine loss. With the Solar heater on the roof (not currently being used because of troubleshooting effort) and the cover, we typically kept the pool at 85-86 degrees, which I assume is the perfect temp to really give algae/organics a place to thrive. So we would be just keeping a balance to prevent take over and higher chlorine loss. I am mentally ok with that as long 3ppm chlorine loss over a 24hr period is "acceptable" given the pool is covered all day.

Now that I think about it, of course UV is not good for chlorine and sunlight aids in algae growth, but if the pool cover was open more often the sun/UV would probably act as a sterilizer to some degree, right? So having the pool cover closed pretty much all the time limits the amount of UV sterilization that occurs? Or is it better to forgo possible UV sterilization and just keep the pool covered all the time?

As for last nights OCLT, it for some reason didn't go very well with my measurements. The SWCG is currently set to 0% and 10am yesterday I read the pool at 18fC. Then last night at 8:15pm I thought i was just as meticulous as always but my 10ml sample read 20fC. I was in a rush and should have taken another sample, but didn't. I left the cover open all night and this morning at 8am I took 2 samples and both were 18-18.5fC. Must have been just a little too much powder last night (maybe I compressed it instead of scraping it) and the 20fc was not really 20fC. I will keep tracking.

I also did a thorough brushing of the pool and all of its crevices today. The only place that visually benefited from a scrubbing was inside the skimmer box

Anyways, hopefully I can do another OCLT tonight and see what happens.

 

[Bperry]

Ok. so if the cover stays closed all day (no UV loss from daylight) and we are losing ~3ppm fC everyday and generating ~3ppm fC everyday, then its simply the organics causing Chlorine loss. With the Solar heater on the roof (not currently being used because of troubleshooting effort) and the cover, we typically kept the pool at 85-86 degrees, which I assume is the perfect temp to really give algae/organics a place to thrive. So we would be just keeping a balance to prevent take over and higher chlorine loss. I am mentally ok with that as long 3ppm chlorine loss over a 24hr period is "acceptable" given the pool is covered all day.

Now that I think about it, of course UV is not good for chlorine and sunlight aids in algae growth, but if the pool cover was open more often the sun/UV would probably act as a sterilizer to some degree, right? So having the pool cover closed pretty much all the time limits the amount of UV sterilization that occurs? Or is it better to forgo possible UV sterilization and just keep the pool covered all the time?

As for last nights OCLT, it for some reason didn't go very well with my measurements. The SWCG is currently set to 0% and 10am yesterday I read the pool at 18fC. Then last night at 8:15pm I thought i was just as meticulous as always but my 10ml sample read 20fC. I was in a rush and should have taken another sample, but didn't. I left the cover open all night and this morning at 8am I took 2 samples and both were 18-18.5fC. Must have been just a little too much powder last night (maybe I compressed it instead of scraping it) and the 20fc was not really 20fC. I will keep tracking.

I also did a thorough brushing of the pool and all of its crevices today. The only place that visually benefited from a scrubbing was inside the skimmer box

Anyways, hopefully I can do another OCLT tonight and see what happens.

The powder amount doesn’t affect the test as long as there’s a few undissolved particles in there it’s fine. Note that heat also degrades chlorine, not just UV.

 

[an1vrsy]

if the pool cover was open more often the sun/UV would probably act as a sterilizer to some degree, right?

No, chlorine is what sterilizes pool water. Maintain per the FC/CYA chart.

just keep the pool covered all the time?

Your pool, nice looking covered pool from the photo you posted, by the way. But what’s the point in keeping it covered? In your case, I saw lots of trees surrounding your pool area. Which when you get the Santa Ana winds, without the cover, you’d have a lot leaves to cleanup. When the winds are not blowing, enjoy the view of the water.

As for last nights OCLT, it for some reason didn't go very well with my measurements.

Personally, I would wait till FC had gotten down to around 10 to do the OCLT.

Your CYA is 40 (round up) which means your SLAM level FC is 16. You are above SLAM level when your FC is 18+ so good thing you’re not using the pool.

 

[Kilkennyeddie]

Phosphates don’t matter if there’s adequate chlorine.

I was having major problems with my SWCG not producing to keep adequate levels of chlorine. I put liquid chlorine in to bump it to 6, withing 2 days chlorine was gone. Put half a bottle of No-phos in, ran pump 24 hours, cleaned filter, SWCG now maintains Chlorine at 2-3 with SWCG running at 50%. So you got me

 

[Donldson]

So you got me

You are keeping your FC level a bit low, for one.

Your situation indicates you had an algae problem. Your iChlor 30 produces half a pound of chlorine gas at 50%, which equates to 4.6 ppm FC in your pool daily. That's a lot of chlorine to be burning through, which may indicate the algae problem has not actually been solved.

 

[Newdude]

SWCG now maintains Chlorine at 2-3 with SWCG running at 50%. So you got me

When do you test with regards to cell production ? That's every bit as important as testing in the first place. If the 2 to 3 that you're testing is at the low FC point of the 24 hours cycle, you actually run 3 to 6 (?) and may be ok. If the 2 to 3 is after the cell added the days FC, you're likely running 0 to 3 and its a recipe for disaster.

 

[Bperry]

I was having major problems with my SWCG not producing to keep adequate levels of chlorine. I put liquid chlorine in to bump it to 6, withing 2 days chlorine was gone. Put half a bottle of No-phos in, ran pump 24 hours, cleaned filter, SWCG now maintains Chlorine at 2-3 with SWCG running at 50%. So you got me

Keeping your chlorine that low is likely to lead down a repeat path of algae and maybe why it happened in the first place. Your pool needs 2-4ppm of chlorine each day. Trying to keep it at 2 means it can get down to zero on an extra sunny/dirty day. If you just maintain the chlorine at a more appropriate level, the phosphates wouldn’t matter.

 

[Kilkennyeddie]

When do you test with regards to cell production ? That's every bit as important as testing in the first place. If the 2 to 3 that you're testing is at the low FC point of the 24 hours cycle, you actually run 3 to 6 (?) and may be ok. If the 2 to 3 is after the cell added the days FC, you're likely running 0 to 3 and its a recipe for disaster.

I always take my test reading in the AM, pumps been only running an hour. And I was incorrect, my readings in the AM are typically 3.5 to 5.

 

[Newdude]

And I was incorrect, my readings in the AM are typically 3.5 to 5

Ok. So you're testing almost at the low FC point of the day, it's still above minimum at that time, and then the FC increases after.

That's a HUGE detail in the equation.

It's also dancing way to close to minimum for my liking. The closer you play with fire, the more likely you get burned. Target on the high side of in range (40 CYA, always round up).

If you want to run the pool on easy mode, target above range to fall back into range at the low point of the day. Look how much (Totally safe) leeway you have above target range, and how little you have below it.

 

[TaylorN]

Your pool, nice looking covered pool from the photo you posted, by the way. But what’s the point in keeping it covered? In your case, I saw lots of trees surrounding your pool area. Which when you get the Santa Ana winds, without the cover, you’d have a lot leaves to cleanup. When the winds are not blowing, enjoy the view of the water.

Thanks. Yeah, the nearby eucalyptus trees rain down leaves even when there aren't Santa Ana winds. But we primarily keep the pool covered to prevent water loss (evaporation), add warmth (the cover heats the pool), and prevent heat loss (from the solar array or cover). Those are all directly related, right. I do love looking at the open pool, but water costs a fortune in San Diego, especially when you like to maintain a really warm pool for the kids and wife

Personally, I would wait till FC had gotten down to around 10 to do the OCLT.

Why would you wait to do the OCLT until 10ppm fC? Because you can realistically switch to the more accurate 25mL/0.2 test instead of the 10mL/0.5 test?

Your CYA is 40 (round up) which means your SLAM level FC is 16. You are above SLAM level when your FC is 18+ so good thing you’re not using the pool.

Yeah, I wasn't letting my family near the pool at 18+ppm with 30-35 CYA. lol!!!

 

[Bperry]

Yeah, I wasn't letting my family near the pool at 18+ppm with 30-35 CYA. lol!!!

Just in case it wasn’t obvious, they can swim once it gets down to 16ppm

 

[TaylorN]

You are keeping your FC level a bit low, for one.

Your situation indicates you had an algae problem. Your iChlor 30 produces half a pound of chlorine gas at 50%, which equates to 4.6 ppm FC in your pool daily. That's a lot of chlorine to be burning through, which may indicate the algae problem has not actually been solved.

Yeah, I now totally agree. Looking back we were just not maintaining a high enough minimum free chlorine level. Per the advice of everyone so far, my plan is to shoot for a CYA of 80 and stay above 7ppm if taking measurements in the morning.

 

[TaylorN]

When do you test with regards to cell production ? That's every bit as important as testing in the first place. If the 2 to 3 that you're testing is at the low FC point of the 24 hours cycle, you actually run 3 to 6 (?) and may be ok. If the 2 to 3 is after the cell added the days FC, you're likely running 0 to 3 and its a recipe for disaster.

Hey dude. I was taking measurements every morning and every evening while the problem was occurring. I didn't want to present that much detail in the posts until someone asked. Its those measurement that had me concerned, because with the SWCG operating at 100% the chlorine level was not rising throughout the day. After an 8 hour run of the pool pump the chlorine level in the morning matched the evening measurement. So there was definitely something major consuming the chlorine throughout the day with the cover closed.

Much appreciate you covering all angles!

 

[TaylorN]

Keeping your chlorine that low is likely to lead down a repeat path of algae and maybe why it happened in the first place. Your pool needs 2-4ppm of chlorine each day. Trying to keep it at 2 means it can get down to zero on an extra sunny/dirty day. If you just maintain the chlorine at a more appropriate level, the phosphates wouldn’t matter.

I concur! Thanks man!

 

[TaylorN]

Just in case it wasn’t obvious, they can swim once it gets down to 16ppm

Thank you for clarifying. SLAM level or above, for a given amount of CYA, is unsafe. But up to SLAM is safe. Got it!

 

[TaylorN]

Ok. So you're testing almost at the low FC point of the day, it's still above minimum at that time, and then the FC increases after.

That's a HUGE detail in the equation.

It's also dancing way to close to minimum for my liking. The closer you play with fire, the more likely you get burned. Target on the high side of in range (40 CYA, always round up). View attachment 530363

If you want to run the pool on easy mode, target above range to fall back into range at the low point of the day. Look how much (Totally safe) leeway you have above target range, and how little you have below it.

Going to do that from here on out. Thanks for all the time you all have spent holding my hand though this! Seriously!