SLAM-ing. Where is the demand?

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shacke

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Jul 5, 2010
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earlier this year I had to SLAM and I will stand up and confess. I failed the 3rd piece by not checking the OCLT. CC was 0.5 and the water was clear. I think that set me up for this need to slam again.

I came back from a week vacation and it was a bit cloudy - so I knew I had a demand since I dumped 5 GAL liquid in there before I left. Once again I am slam-ing and the water has been crystal clear since day 2.

The CC has always been borderline 0.5 (it takes the second drop to go from faintest pink to super clear). My CYA is 20 (despite adding gallons and gallons this year). I am keeping my FC levels over shock level (at least 15). pH and Ta are fine.

I am keeping on it. I am brushing and it seems pretty clean - some slight dust in the places the turno floor cleaners send dirt. Otherwise very nice!

This is day 4.

My FC last night was 23. At 7:30 this am it is 16. Each night it gets munched away.

My assumption is there has to be algae. If so, why such a huge overnight demand and I can't really see it? Is it typical for algae to be totally invisible and yet be SO very hungry for chlorine?

I suspect the answer is yes - maybe just need some validation since it is a rough exercise!!

Thanks!
 
Yes, that is frustrating. I'm currently in SLAM mode myself, so we're all prone to odd things happening with clear water. But when your FC gets lost during hours of darkness, especially by that much, it's organic - algae. Somewhere, somehow, it's in your system. All you can do if follow the basics on the Pool School - SLAM - Shock Level And Maintain page and investigate EVERYTHING your water comes in contact with. Check any small gaps, pathways for water, light fixtures, etc. You can't take anything for granted. Like I said, I am SLAMming too. My water is crystal, no CC to speak of, but I am using just a little too much bleach each day. Sure enough, I failed my OCLT this morning by 3 ppm. So I'm not taking any chances. Get it done quickly before it gets worse. You'll get it, just make sure you check every little spot where water flows and you'll pass.

- - - Updated - - -

Oh, after re-reading your post .. something else jumped out at me .... You have a SWG, but your CYA is only 20. Remember, based on the Pool School - Chlorine / CYA Chart it is supposed to be between 70-80. That, coupled with your FC levels, should all be in alignment. Perhaps that's one reason why you are having some difficulties.

- - - Updated - - -

Also, just to confirm, is your SWG turned-off each night when you are performing the OLCT? Once you take that last FC reading at night, there should be nothing else adding FC to the water so you get a true FC reading in the morning. Just wanted to make sure. :)
 
Thank you. The SWG is off, and has been off - since I can't figure out why my CYA levels don't rise.

The Chlorine issue is what is most concerning to me! Seems like an awful lot of overnight chlorine demand.

I will have to see about taking the light fixture off, since that is the only place I can't see easily.
 
Have you noticed anything strange with your DE, like the pressure being different than usual after backflushing? Are you backflushing per this thread Use-and-care-for-DE-filters? I had trouble getting an OCLT result until I opened my DE filter and found it partially clogged and full of black nastiness. Time will tell, but I think it was clogging because I was not repeatedly flushing per that thread and I was adding a complete charge of DE each time instead of 80% thereby overfilling and clogging it. Then the areas of little or no flow due to clogging were perfect for algae to really take hold.
 
bkfamily1 said:
Have you noticed anything strange with your DE, like the pressure being different than usual after backflushing? Are you backflushing per this thread Use-and-care-for-DE-filters? I had trouble getting an OCLT result until I opened my DE filter and found it partially clogged and full of black nastiness. Time will tell, but I think it was clogging because I was not repeatedly flushing per that thread and I was adding a complete charge of DE each time instead of 80% thereby overfilling and clogging it. Then the areas of little or no flow due to clogging were perfect for algae to really take hold.
Click to expand...


Hmmm. Interesting. I have become VERY DIY with the chemicals but not with the other stuff. I have never attempted to actually OPEN my filter and brave the innards. I have been noticing some strangeness with the filter pressures - mainly the need to backflush more for some reason. I will read that thread and see if I can learn anything from it.

Thank you. I would love to be able to expand my DIY knowledge to the filter :D
 
You are learning SO much! Great job!

Now lets learn that filter! Do you have the manual? Can you figure out the model so you can search for the manual?

Once you can figure out the model you can post on the equipment part of the forum and get any help you need.

Or keep it here and we might be able to help.

Kim
 
Have you been getting a lot of rain? We have in SW PA. Rain can be why your CYA is so low and not rising, especially if you're draining water off the pool.
 

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Had an idea.

Why don't I do the oclt with the filter OFF. If there is a huge difference (meaning it improves) with the lack of water going through the filter, doesn't that help to exlclude algae there? The FC in the pool won't circulate through the grids.

I will check the light as well, but I just can't see how that small space would eat 9ppm of FC an evening.

Thoughts?

Thanks :)
 
Shacke,

You are sort of missing the point. First, there is likely no algae in your filter........it just doesn't grow there. That said, bypassing it to pass the OCLT is not right. You need your filter on to operate your pool so "tricking" your way into passing (which won't work anyway) is bad practice.

You have organics (algae in) your pool and the answer to that is chlorine and lots of it until the algae is killed. Go back and reread the SLAM and understand that you MUST continually have high levels of chlorine to fix your pool.
 
shacke said:
Hmmm. Interesting. I have become VERY DIY with the chemicals but not with the other stuff. I have never attempted to actually OPEN my filter and brave the innards. I have been noticing some strangeness with the filter pressures - mainly the need to backflush more for some reason. I will read that thread and see if I can learn anything from it.

Thank you. I would love to be able to expand my DIY knowledge to the filter :D
Click to expand...

it looks like you have hayward equipment, here is a video of cleaning a hayward de filter Cleaning a Hayward Pro-Grid, Micro-Clear, Super Star-Clear D.E. Filter - YouTube
 
shacke said:
I will check the light as well, but I just can't see how that small space would eat 9ppm of FC an evening.
Click to expand...

You would not believe how many pools will NOT clear up due to "that small space" being SO full of algae! I am going to post a link to a thread. This thread shows it very well! Look at post #58. He made a graph to show his SLAM. He even notes where he took his light out.

Think it's time to take back my pool... - Page 3

Kim
 
duraleigh said:
Shacke,

You are sort of missing the point. First, there is likely no algae in your filter........it just doesn't grow there. That said, bypassing it to pass the OCLT is not right. You need your filter on to operate your pool so "tricking" your way into passing (which won't work anyway) is bad practice.

You have organics (algae in) your pool and the answer to that is chlorine and lots of it until the algae is killed. Go back and reread the SLAM and understand that you MUST continually have high levels of chlorine to fix your pool.
Click to expand...

Thanks Dave. I suggested that thinking that the filter would be a place where algae can hide, stubbornly caked in there with the DE. If I bypassed the filter during the oclt and I passed that would confirm the algae was in the filter not the pool.

Now if you really think algae isn't lurking in my filter grids, (and u know better than I) it says me a lot of time removing and washing them. But if the light is clear .... I will be totally stumped. The pool water looks like glass and I'm vacuuming up virtually nothing yet my FC consumption is huge.

I'll keep trying and that light will come out Sunday when I can get in there.
 
your filter should be changed/cleaned based on flow, not algae. algae tends to grow where there is stagnant water flow and its not being exposed to the chlorine in the water...like behind a light, under the ladder etc. your pool filter is not one of those, high flow and constant exposure to chlorine. so no, its not a place to worry about. it will remove the dead algae from your pool, and any live algae in there is being bombarded by chlorinated water and will quickly die. you need to clean/backwash your filter when its operating 25% higher pressure than freshly clean.

algae is NOT a filtration problem, its a chlorine/chemistry issue.

- - - Updated - - -

and I think you are overestimating the impact of a ton of algae behind a light fixture can have on your FC levels.
 
I would just like to briefly reiterate the poor flow and clogging issues I encountered in my DE filter and the heavy pockets of algae I found in the filter where there was little or no flow. That may very well not be the problem in this case. And I am sure you are correct that it is probably almost always not the filter. And maybe it was coincidence and not really my problem. But I had the same issue - crystal clear water and no visible algae but a continuing chlorine demand. And I finally got it resolved when I found the black nastiness in the DE filter and cleaned it out.
 
bkfamily1 said:
I would just like to briefly reiterate the poor flow and clogging issues I encountered in my DE filter and the heavy pockets of algae I found in the filter where there was little or no flow. That may very well not be the problem in this case. And I am sure you are correct that it is probably almost always not the filter. And maybe it was coincidence and not really my problem. But I had the same issue - crystal clear water and no visible algae but a continuing chlorine demand. And I finally got it resolved when I found the black nastiness in the DE filter and cleaned it out.
Click to expand...

if you had poor flow, then yes you need to clean the filter. its going to accumulate stuff, that's the point of the filter :) of course you will have algae in your filter, its removing it from the water. the point is, its no different being in the filter than it is floating around in the pool as it relates to FC consumption. just like in the pool itself, if your FC levels are kept up to SLAM, the algae is getting killed. all the dead algae accumulates in your filter since its being removed from the water. when it starts to clog you have to clean/backwash.
 

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