Can FC consumption behave this way ?

[SPP]

Dear Seniors,

I am helping my friend with cloudy pool issue. His equipment is 100% similiar to mine but for now less the ozone generator.
He also does not have a back up pump on trolley, but he runs his pumps 22 hours a day.
I have yet to install the flowmeters I bought for him, so I can't say the turnover. My estimate for his pool is about 12 hours per turnover based on pump curve and plumbing/filter resistance. He has a separate pump for the robot and I been using that with the Slime Bag filter to make it like an extra filter for prevention of circulation dead spot in the kids pool attached to the main pool.

Initially I thought the pool has calcium clouding issue because being a concrete & ceramic tiled pool with CH 70 is low as per reccomended table. The pool did cloud once 4 months ago but with mild FC bombing, approx 3PPM a day of bleach worth for like 7 days non stop took care of the clouding. That was before I have TF test kit. So I can't give proper FC and CC level

The CYA level is either 10 and maximum is 15. Hard to see that black dot at this level.

The question is, can sudden high FC level actually create sudden green algae bloom from where it was initially only cloudy ?

Why I am asking this is, I picture cloudy water from algae is like micro baby algae that is not as strong as adult green algae... So if I raise FC level to shock level for a cloudy water, I would expect the baby will die and no time to become adult. ... . So when the adult algae came....I was so dissapointed because initially, I thought it was calcium clouding....

I am kind of upset over this cloudy pool issue because no CC at all registered, FC consumption normal and suddenly cloudy even with a 2.5 FC average at 10-15 PPM CYA. Even when cloudy the FC level consumption is within limits of its daily loss , as this is an outdoor pool unshaded. So when I finally decided to bomb to 10 FC, then...abracadabra the green algae start to appear... ...I was confused because how come no obvious extra FC consumption if this cloudiness was because of baby algae ? I thought FC consumption can tell if organics are feeding on the chlorine without waiting for green bloom or even having any cloudiness.

If this is a horror movie this is : " The Sleepers "....

So what actually happened here ?

The pool should clear soon. I sent my back up pump on trolley there.
I just had it floc after the green bloom and the overnite FC consumption was already NIL.

Thanks as always..

 

[chem geek]

If the CH is really low, 70 as you said, then that's not going to be clouding from calcium. It's when the saturation index is high, so higher pH, TA and CH, that you can get either scaling or cloudiness from over-saturation. The low CH would mean that the water could be dissolving plaster, but it wouldn't cloud up as the plaster would dissolve and not be seen.

As for chlorine turning the water green, that is mostly likely copper since adding a hypochlorite source of chlorine raises the pH and higher pH will precipitate out copper. Was a copper-based algaecide ever used or was the pool ever at very low pH or Trichlor pucks every put into a skimmer going through a copper heat exchanger in a gas heater?

Richard

 

[SPP]

Hello Richard,

Thanks for the tips.
The pool has two seperate pumps and two seperate Pentair heater. I got my friend to make a bypass valve for those heaters. Its giving resistance in plumbing when not in use and for the same worry of it corroding prematurely. So no heater in the circuit for this case, it was never turned on.

The pool has electronic copper/silver ionizer like mine but its reading 0.3ppm only. I too worry about possible elevated copper level. I did not use any sort of copper based algaecide ( liquid or powder ). I purely bombed all the way to a calculated 10 ppm FC. Ph is always maintained at 7.4 to 7.6. Before I use lots of 12.5% bleach, I added MA first. PH is always decent.

Cross checking the FC consumption again, I think there is a mistake somehwere. In order to gain CYA, I told the pool boy to start using the Trichlor again after I tested it only had 10-15PPM CYA some two weeks ago. What I did not know that the Trichlor being located on the gutter ( no feeder unit ) where waterflow is best to dissolve it, actually dissolved in 2 days. Looking at the previous log book it shows FC rise by 1PPM the next 24 hours it was added, however that old log book was when OTO test were used. So there is another window of fault. The yellow color interpretation of the OTO is easily off by 1 PPM when above 1.5 - 2 PPM worth of yellow is seen, depending on whose eyes. I told the pool boy to stop using trichlor until I have the TF-100 test kit for him. That was about last July. I am sure now the CYA should have gone up but with cloudy water I rather wait till its clear to test CYA. I told the pool boy to stop after 20 tablets of 3" trichlor total the day I told him to start using trichlor again when it was 10-15 PPM CYA. I am hoping to hit 30 PPM CYA as final number, eventually.
This is a 60,000 gallons pool.

The trichlor is a 3" tablet which I believe is 200 gram, since 1 tube contains 5 = 1kg packaging for sure. Pool Calculator showed that 1PPM needs 246 grams. I am sure it means 246 gram is to be dissolved sooner than 24 hours.
My personal use with trichlor previously has also been how diificult it dissolves in my own pool, even when dumped it in my balancing tank where the waterflow is good.

So I thought one 3" tablet will be gone in 24 hours, that's how I profiled its consumption, unknowingly its size balance after 24 hours is half the shape, so its 1.5" size not a complete zero.

So my mistake in calculating the FC consumption seems to come from combining trichlor and 12.5% bleach at the same time and most test are carried out at 11:00 AM where I must compensate for sunligh eating away the FC. I must have over compensated the sun eating FC on some days.

CYA takes like a week to be effective right ?

I am sure it was my calculation mistake on some days in the calculation which I started as of 20th August, the day it went cloudy. There are some days like 24th to 27th that shows a steady loss and I purposely do not add anything. Starting at 3.5 FC and to 1.0 FC in 3 days. This period probably made me thought that nothing organic is eating the FC except sunlight and so I lean towards possible calcium clouding.

It shows high FC consumption only when I stated to bomb to target 10 FC on the 28th upwards. I read that FC loss is a percentage from sunlight ...like 30% or so a day.....but never mind, I am already seeing green water and been trapping algae on the Slime Bag filters.

The day the over nite FC stayed good between 5PM to 7AM and I was trying to repeat it for the past two days and it rained hard every 4PM upwards.... .

This is a 100% algae but just rather odd the way it goes from cloudy to algae and its FC eating habits... . I hope its not a diet program by the algae. Eat only when they are plenty FC....

Can this scenario be happening Richard ? :
Assuming I have a tough algae. If free chlorine does not kill algae, it doesn't get consumed right ? So the algae happily live in a decently high... say 3.5 PPM FC, it doesn't get killed and thus my FC numbers stayed, except from sunlight loss. The moment I bombed with a calculated 10 PPM FC, the algae started to get killed in numbers...hence I can see significant FC loss from killing and from burning off those dead algae. Is such a scenario possible ?

Thanks again.

Later,
Surya

 

[JasonLion]

CYA added via trichlor should be effective as soon as the tablet dissolves.

If there is algae in the pool and you aren't adding chlorine continuously the FC level will go to zero. Sometimes, with trichlor or a SWG, the algae and chlorine additions can "balance out" and there can be a low level of algae and some chlorine in the water, but chlorine consumption will be much higher than it otherwise would be.

 

[SPP]

Thank you Jason. The FC loss to sunlight in my friend's pool is what made me confused sometimes because in strong sunlight and cloudy sky it differs.

If this pool had TF-100 kit earlier I would have been able to profile better. I would want a 7AM and 5PM test everyday for a week, later when the pool is already clear. I want check its FC loss due to sunlight in a more accurate manner.

I am beginning to do this for my own pool but my pool is shaded. His pool is 90% direct sunlight and the house blocking sunlight partially. At least strong direct sunlight for 5 hours a day is possible. Even we are in the tropics, our sunlight radiation ( insolation ) in this city is only like 3.5 hours a day based on the chart I have. Some of you guys in the US actually get more. His day time water temp can hit 30*C due to the dark blue color of the ceramic used as pool shell. What this pool gain in CC removal by sunlight probably also contribute higher possibility of algae since water temp is that high.

In my pool, I loose 0.5ppm when cloudy and in worst of the worse sun I loose 1ppm. Based on 1.5FC as the minimum level at 25PPM CYA, PH 7.6. I am now dosing to 2.5 FC as the high range. I don't have Liquidator, so my FC level climbed fast every time the 12% bleach dumped in pool by broadcasting it the best way my pool boy could.

 

[chem geek]

This is why we frequently talk about an FC drop overnight since that eliminates the sunlight factor. As for an alage outbreak, visible quantities of algae use up a LOT of chlorine so even if you were to measure an FC in one area of the pool, in areas near the algae it can get closer to zero. This is why one needs to shock the pool with higher FC when there is visible algae or even cloudiness to get ahead of the algae growth and make up for localized depletion compared to normal maintenance levels of FC.

 

[SPP]

Thanks Gentlemen. I will treat cloudy as possible algae first and immediately bomb away. It was such a waste of time and so frustrating. If I had bombed 10-12 FC on 20th Aug, by today the pool would have been clear....