Help Finding the FC Eating Monster

[bobandsherry]

First, yes, I know I need to SLAM and I am in the midst of it again. However I want to figure out just what may be eating my FC as I just completed a SLAM a month ago. UGH Results were looking good as I've summarized below:

I completed a SLAM on 7/27, passed the OCLT. Turned my SWG back on, set it to 30% (or about 2.5FC/day). Results looked good for a couple weeks, FC was holding nicely in the 10-12 range (held it high just to ensure that things were all clear). Fluctuations during the early AM and then late PM due to heavy UV from southern exposure sun. Thought that with only 2.5FC/day that was running well given heat and sun. Things looked like SLAM was indeed all clear....

But then.... I then noticed that my FC dropped slightly on 8/8, so I increased the SWG to 40%. Noticed the FC dropped again so increased SWG to 50%. The FC dropped again within a few days and bumped up to 60%. Still didn't hold it's own, ran it to 100% and watched what was going on. At this level my SWG was producing over 8FC per day and FC just kept dropping.

Here's a chart of my FC (scale on left) and SWG (scale on right) for this time period:

Honestly, the pool looks crystal clear. Here's pics I took as I was brushing today (notice that even with my brushing the water still looks very clear). Inside the skimmer is clear. Nothing visible around the light.

Last test results prior to starting slam this time:
FC: 6.4
CC: 0.2
pH: 7.8
TA: 60
CH:370
CYA: 60 (actually was 40)
Salt: 3100 (my salt cell and K1766 results are the same)

And also, I've tested for phosphates (using K-1106 test), basically 0 phosphates as there was a very minimal blue tint, much fainter than even the 50 ppb reference color chart. Lastly, I did a backwash just over a week ago.

Note: I was shooting for CYA to be 60, but as it turns out my cataracts caused me to see dot missing at 60. Got new lens and see it's actually 40. Since last nights OCLT failed it's not the CYA that's the issue, and as it turns out it works to my benefit as I don't have to shoot the FC as high for SLAM.

So sorry for long message, but trying to share as much info as possible.

Thanks for any suggestions

 

[Spa Owner]

Would you mind doing a test on the incoming water used to fill the pool? Is this from municipal mains?

What is outside the pool fence? I think I see ocean but want to check.

Have you noted any specific change to weather, wind, sun time etc around the days you note the increased demand?

Is the cell clean?

http://www.prolinedist.com/wp-content/uploads/GL-AQR-Disgnostic-Manual-r1.58-2011.pdf

 

[Poolzzz]

Since last nights OCLT failed...

What were the actual results (evening and morning readings) ?

 

[bobandsherry]

The fill water is from municipal. But thanks to the liquid sunshine here I have not added any fill water in past several months. Something in particular you would be looking for?

Outside the screen enclosure is large retention pond.

No real noticeable changes, perhaps more sun. Just thumbing through what Pool Math records, pretty much the same. Here's a chart that shows temps and rain for past 30 days.

Cell is clean, no build up present. Here are the current readings, 26.2/4.53 (instant salt = 3100) and 26.3/4.05 (instant salt 2700) --- Note I just checked the reading again, and the 2nd reading shows as 26.6/3.84

 

[bobandsherry]

What were the actual results (evening and morning readings) ?

Here's from last night for the start of my OCLT (loss of 6.5FC)
8/24 8:49PM - 16.0
8/25 7:26AM - 9.5

Here's from prior nights, SWG was on, so I don't consider these of OCLT, but with SWG running at 100% it is an interesting reference point especially as it shows the increased overnight consumption over a week's time period:
8/23 7:55PM - 7.6
8/24 7:46AM - 7.6 <<-- no change in 12 hours SWG production = 100%

8/21 10:28PM - 11
8/22 8:19AM - 12.5 <<-- 1.5 increase in 10 hours SWG production = 90%

8/17 8:12PM - 5.8
8/18 7:10AM - 9.2 <<-- 3.4 increase in 11 hours SWG production = 100%

By comparison, here's what PM/AM results were earlier in the month:
8/3 6:39PM - 10.5
8/4 7:59AM - 12.0 <<-- 2.5 increase in 14 hours SWG production = 30%

 

[mouse23]

I abandoned my SWG because it was too temperamental and costly on parts without desired results.
Then I adopted the Borax methodology with manual chlorine applications. What a difference.
Water feels better, looks better and the borax appears to work as an algae stat.
With my new variable speed pump and the tip from TFP that circulation does nothing to algae
I save enough to keep chlorine level high (6). I haven't shocked in three weeks. Keeping fingers crossed.

 

[bobandsherry]

Don't look to abandon my SWG. Since my OCLT shows a drop it's not the fault of my SWG. Went through SLAM earlier this year as well. Pool is always clear so there's something lurking somewhere.

 

[Spa Owner]

The fill water is from municipal. But thanks to the liquid sunshine here I have not added any fill water in past several months. Something in particular you would be looking for?

Outside the screen enclosure is large retention pond.

No real noticeable changes, perhaps more sun. Just thumbing through what Pool Math records, pretty much the same. Here's a chart that shows temps and rain for past 30 days.

Cell is clean, no build up present. Here are the current readings, 26.2/4.53 (instant salt = 3100) and 26.3/4.05 (instant salt 2700) --- Note I just checked the reading again, and the 2nd reading shows as 26.6/3.84

The chlorine demand increase is occurring more or less a day or two after the rain events. I think its likely an environmental pollutant is being added to the water body.

The retention pond. What is it retention for rain water? Road run off?

 

[Catanzaro]

Then I adopted the Borax methodology with manual chlorine applications. What a difference.
Water feels better, looks better and the borax appears to work as an algae stat.

Please explain? The borax methodology, that is.

 

[bobandsherry]

The chlorine demand increase is occurring more or less a day or two after the rain events. I think its likely an environmental pollutant is being added to the water body.

The retention pond. What is it retention for rain water? Road run off?

Interesting observation, but what would be in the environment that would cause the pool water to be significantly impacted? When I've slammed before it's been after some extended rainy periods, so could be onto something.

Retention pond is for run off from anything and everything. It is interconnected with several other ponds in the community, and then interconnected with ponds outside the community. Pond is much lower than pool so there's no chance it is leaching into the pool. What's your thoughts on retention pond affecting the pool?

 

[Poolzzz]

How often do you run your water features?

What about animals in the pool?

The retention pond sounded promising but if no chance it's leeching into pool then guess not. What about run off in general getting into the pool? Although near zero phosphates might argue against environmental influences (not sure on that just thinking a lot of chemicals have phosphates as does organic matter).

 

[Jimrahbe]

I haven't shocked in three weeks. Keeping fingers crossed.

I use a SWCG and have not shocked my pool in over 4 years...

People are temperamental, SWCGs are not...

Jim R.

 

[bobandsherry]

How often do you run your water features?

What about animals in the pool?

The retention pond sounded promising but if no chance it's leeching into pool then guess not. What about run off in general getting into the pool? Although near zero phosphates might argue against environmental influences (not sure on that just thinking a lot of chemicals have phosphates as does organic matter).

Since the last SLAM I've kept my water features running all the time, just to prevent anything from wanting to sprout up there.

Being in FL, the area I'm in has phosphate mining all around me, so that was a concern. But have tested several times since I got the test kit and all is good there. Def no chance of pond leaching in, has never got even close.

No animals in the pool, other than a couple of baby frogs I found a month ago. But nothing regularly. Only an occasional lizzard in the enclosure but never in the water. No plants in the enclosure either, so no organic material there.

The only chance of any run off would be from pavers. However those are pitched away from pool and I haven't seen flow into the pool and have drain strip. But could be some minor trickle I suppose. But can't think of what would be present on the pavers. They are sealed and have polymer sand.

I did experience similar issue around this time last year, so the whole environment theory would be an interesting path, but can't find anything that points to a causation. Which is why I reached out here as I've tried to figure that out but obviously unsuccessful.

When you look at the water, you'd not think there's any issue. I even ran water sample to pool store to see if they came up with anything they would find, but nope. They gave my water a clean bill of health, other than FC being high, but that was intentional so I would hopefully prevent this issue.

Scratching my head and still hopeful there's something I'm overlooking.

 

[Poolzzz]

The problem I'm having is your FC levels should be able to handle any environmental sources. Especially with such low phosphates. If the FC is overwhelmed it would show up on your chart the next day because the swg didn't keep up.

However your graph doesn't show any time when FC levels drop even close to minimum. With Cya=40 the minimum is 3. So how does algae get started? Especially with low phosphates. And even when consumption seems to be increasing you have high FC levels which should be preventing the growth.

Could it be your cya is a lot higher than you think? Have you ever tested yourself with the cya 50ppm standard?

When are you tests done relative to swg operation? They should be just before starting to catch the lowest point.

Have you investigated if you have uniform FC distribution throughout the pool? Maybe there are areas of poor circulation where algae is starting and growing.

Are you sure you have algae? By that I mean are you definitely failing OCLT? Tested more than once? Just thinking late in the year you start having this problem shown by needing to increase swg output. Perhaps it is just cya burning off during the summer and needing swg turned up to compensate. You are now at 40 which is low for a swg. And you do say your water is crystal clear which doesn't seem consistent with an overnight loss of 6.5 FC. My water would be cloudy with that amount of overnight loss. Testing error?

Well that's about all I've got off the top of my head. Hopefully someone can figure it out!

 

[Spa Owner]

Interesting observation, but what would be in the environment that would cause the pool water to be significantly impacted? When I've slammed before it's been after some extended rainy periods, so could be onto something.

Retention pond is for run off from anything and everything. It is interconnected with several other ponds in the community, and then interconnected with ponds outside the community. Pond is much lower than pool so there's no chance it is leaching into the pool. What's your thoughts on retention pond affecting the pool?

I was more curious about the pond. Didn't consider leaching or overflow to pool. That would be very different and I have seen that somewhere else.

My thinking is generally there is something in the atmosphere. I cant say what that is, which is either interfering with the chemicals in the pool or more likely interfering with the chemicals in the test kit to give odd readings.

As I understand it from your post, the pool remains clear and crystal looking however the chlorine levels seem to be dropping. In response the chlorinator output is increased and increased and so on, yet the chlorine testing still shows a dropping level of chlorine. Have I got this correct? No other signs i.e. cloudy water, algae growth or otherwise to report just this lower and lower chlorine reading.

I also think as I read it the chlorine level comes right if the pool is slammed. This may still be consistent with interference with test reagents.

It may be a bit late now as the changes may make it difficult to know for sure, however try turning the chlorinator back down to the original setting and see if there is a drop of chlorine level and a tendency towards clouding or hazing or algae growth. I cant think of another way to rule out interference with the reagent than try and see if something happens. If my guess is close to right I don't think water quality will be impacted and in a few days or a week of clear weather the chlorine level will recover.

 

[Winnie-the-Pool]

First of all, ADMIRABLE JOB on the record keeping and charts!

Since there seems to perhaps be a correlation with the rain, I wonder if something is happening in the environment that causes a buildup on the screen enclosure. Then the rain washes it suddenly into the pool at a rate high enough to overwhelm the chlorine level.

Is it possible an increase, change of turbulence or wind direction combined with splattering caused by the rain in the retention pond allows whatever is in it (probably lots of nasties in there) to become airborne.

Interesting mystery...

 

[cowboycasey]

While I love me some SWG they do not "raise" your FC level well, you need to do that with liquid chlorine... If I see my FC low I immediately add chlorine to get it up then adjust my SWG to a higher level... you can get 2.5 gallon 12% where your at, I wish I could

From what you have posted it looks like a couple things are happening that starts a slight algae bloom..

1. it rains and lowers your CYA and FC
2. The sun comes out and eats your FC because of lower CYA
3. your keeping your CYA low, you thought it was 60, really 40, and you should have it at 80 or 90..

Recomendation

SLAM until you pass all 3, should only take a day or 2

once complete, raise your CYA to 90 and keep between 80 and 90.. because of the rain where you live you may have to test and add monthly
start by running your pump 10 hours a day at 30% and see what that gives you... I keep my FC between 6 and 10, yes it uses more chlorine/SWG but I do not care, my pool has been clear for 3 years running it this way...

Hope this helps

 

[bobandsherry]

The problem I'm having is your FC levels should be able to handle any environmental sources. Especially with such low phosphates. If the FC is overwhelmed it would show up on your chart the next day because the swg didn't keep up.

However your graph doesn't show any time when FC levels drop even close to minimum. With Cya=40 the minimum is 3. So how does algae get started? Especially with low phosphates. And even when consumption seems to be increasing you have high FC levels which should be preventing the growth.

Could it be your cya is a lot higher than you think? Have you ever tested yourself with the cya 50ppm standard?

I had thought that I was keeping CYA at 60, but turns out it was 40. Cataract surgery this week shows just how cloudy my vision was, seeing sharp now I see the CYA is 40. But even if it was as high as 80 the FC never dropped below the minimum. I was keeping the FC high just to keep myself out of another SLAM. I have not tested with 50ppm CYA standard, but testing chemical has expiration of 6/2019, so still far from EOL. Pool store test also confirmed the CYA is close (they never seem to be spot on with any test).

When are you tests done relative to swg operation? They should be just before starting to catch the lowest point.

Have you investigated if you have uniform FC distribution throughout the pool? Maybe there are areas of poor circulation where algae is starting and growing.

I run my SWG 24 hours, so there is no high and low point, just a constant (relative to the % of output) generation of FC. Pump is then also running 24 hours. I have it set to run 4 hours at 2250, then throttle back to 1500 (raised from 1250 it just to ensure that circulation was sufficient). I can check FC levels at various parts of the pool to verify, but overall nothing is visible.

Are you sure you have algae? By that I mean are you definitely failing OCLT? Tested more than once? Just thinking late in the year you start having this problem shown by needing to increase swg output. Perhaps it is just cya burning off during the summer and needing swg turned up to compensate. You are now at 40 which is low for a swg. And you do say your water is crystal clear which doesn't seem consistent with an overnight loss of 6.5 FC. My water would be cloudy with that amount of overnight loss. Testing error?

To look at my pool I'd say no algae, but OCLT says there's something. OCLT last night,
8:34 PM - 20
7:18 AM - 16 <<<<--- drop of 4, fail OCLT (ugh!), which is improved from nigh prior which was drop of 6.5, so SLAM in process working

The increased and high daily FC consumption prior to SLAM indicates there's something in the water. With SWG running at 100% (and I have my SWG run 24 hours), that's around 8FC daily that was being produced.

I agree with you on water should look cloudy, seen that before. But you see what I see. Testing error perhaps, but that would be a pretty large error, and doing nothing different than I've done in the past. I rinse my test tube, then wipe it out, fill it with pool water to the top and then reduce until at 10ml level. Could be slightly off on getting the 10ml level, but I shoot to keep it consistent so don't think that's it. A drop is a drop, consistent with how I put in the drops.

And my tests during the day is seeing a similar drop with needing to add chlorine. From yesterday, I started with FC at 9.5 (7:26AM), started SLAM and added 15.3FC and ended the day at 20 (8:34PM). So that would give a usage of 4.8 for 13 hours, and for 11 hours overnight 4.0 (which is what my OCLT shows). So ruling out testing error.

Well that's about all I've got off the top of my head. Hopefully someone can figure it out!

I do appreciate you taking the time to make suggestions. As I think I have a pretty good handle on my chemical levels and maintaining the pool, I've been scratching my head as well. So that's why I tossed this out for someone who's maybe been around pools for longer time than I have and perhaps seen something similar.

 

[pookiesunshine]

possibly something in your pipes and/or water features? i've never used it but might you try the Ahh-some product? Have you removed your light fixture to look in the niche? other possible hiding places you have to look behind? just wild guesses.

i forgot to add that Winnie might be on to something too. As a general practice, might be worth a try to add an extra dose of liquid chlorine after a heavy rain.

 

[bobandsherry]

My thinking is generally there is something in the atmosphere. I cant say what that is, which is either interfering with the chemicals in the pool or more likely interfering with the chemicals in the test kit to give odd readings.

As I understand it from your post, the pool remains clear and crystal looking however the chlorine levels seem to be dropping. In response the chlorinator output is increased and increased and so on, yet the chlorine testing still shows a dropping level of chlorine. Have I got this correct? No other signs i.e. cloudy water, algae growth or otherwise to report just this lower and lower chlorine reading.

Roger that. I've run through cloudy pool, but not seeing it this time (which is why I posted so many pictures). Nothing visible to my eye, and with new IOL lens I'm seeing even clearer than before

I also think as I read it the chlorine level comes right if the pool is slammed. This may still be consistent with interference with test reagents.

After last slam the pool was running very well, SWG was set at 30% and was holding for a couple of weeks at that level, minimal changes in the FC level day over day. It rained then, and being in FL it will rain about every day for a brief period in the afternoon.

It may be a bit late now as the changes may make it difficult to know for sure, however try turning the chlorinator back down to the original setting and see if there is a drop of chlorine level and a tendency towards clouding or hazing or algae growth. I cant think of another way to rule out interference with the reagent than try and see if something happens. If my guess is close to right I don't think water quality will be impacted and in a few days or a week of clear weather the chlorine level will recover.

As I'm already on the SLAM path I will continue the course and keep clear of any noticeable bloom. First time I'm reading about interference with the reagents, so intrigued. What have you seen cause that before?

Thanks for taking the time to provide your suggestions.