Algae Spots w/ FC of 4-8

[Matchless1]

So, I had some algae spots (at least I think that's what they were) develop on my walls (mainly inside curves and corners) about a month ago, so I did an OCLT, verified the loss and proceeded with a SLAM for a few days. All has been good until this evening (1 month later) when I noticed more algae spots that seemed to come out of nowhere. I've been maintaining my FC from about 4 - 8 since coming down off the SLAM (daily test results below). So, I'm having the hardest time figuring out what could be causing these spots...again assuming they are algae. Shouldn't the chlorine be killing it before the spots form?

As far as recent changes that I can think of, I started running my pump less per day about a week ago due to the lower temperatures and lack of use. I was running my VS pump at 1700 rpm for 10 hours/day during the summer yielding 2.5 turnovers per day. The last week has been for 6.5 hours/day (still at 1700 rpm) yielding 1.5 turnovers per day. I don't think this would be the cause, but it's just something that's changed recently.

Also, the chlorine I am using is probably approaching 2 months old due to buying a little too much for the last SLAM. BUT, it's 10% concentration (from P-A-P), and as long as I'm maintaining the FC level, I wouldn't think this would matter, but maybe it does.

Other than that, I'm at a complete loss. I really need to figure this out so I don't have to keep SLAMing my pool every month due to these spots that magically appear in a seemingly (to me at least) well kept pool. I plan to do an OCLT tonight. Any and all thoughts/suggestions are welcome. Thanks!

Green/light brown spot (not the orange thing) in center of photo (sorry, I didn't think to take a picture until after I had brushed nearly all the spots off):


Test Results:

 

[jblizzle]

With a CYA of 60ppm, your minimum FC level is 5ppm (target 7-9ppm daily), so you admittedly have been letting it drop too low. See [FC/CYA][/FC/CYA] ... not sure where you got the tool, but the recommendations see to be a little off

Have you been brushing?

 

[Matchless1]

With a CYA of 60ppm, your minimum FC level is 5ppm (target 7-9ppm daily), so you admittedly have been letting it drop too low. See [FC/CYA][/FC/CYA] ... not sure where you got the tool, but the recommendations see to be a little off

Have you been brushing?

You're right. I suppose it did drop below 5 for a few days, but the CYA also fluctuated down to 50 (minimum FC of 4) during that time. I agree it’s borderline, but you made me think about something. I run a Del Ozone unit, which helps reduce chlorine usage (I’ve done my own tests and verified this), which is great. However, obviously the ozone unit only runs when the pump is on. And since I’ve reduced my pump run time (and thus ozone run time) recently, it would make sense that maybe the borderline days may have been just enough time to let it get out of hand before my FC got back up to “target” range. Basically, I think the ozone was keeping me safe (just barely) at the 3-5 FC levels until I reduced the pump run time about a week or so ago.

I guess I’ll go ahead and do the OCLT tonight still, and plan to SLAM again. Then, I guess I’ll need to keep a closer eye on the CYA and target FC range. I honestly don’t know why my CYA has gone up at all lately. I don’t use pucks and I haven’t used pool shock. We’ve had almost no rain in the past month (which would only make it go down, I know), so I’ve had to add a little water here and there, but again, this should only make it go down I would think. Any other things that would contribute to increased CYA?

I brush once a week and run the robot about twice a week.

 

[Jezza]

Likely testing error- the margin for error can be up to +/- 15. It's important to do the CYA under ideally the same conditions- in full sunlight with your back to the sun, taken from waist height. In my experience conducting the test at the same time of the day helps with the consistency.

 

[Matchless1]

Likely testing error- the margin for error can be up to +/- 15. It's important to do the CYA under ideally the same conditions- in full sunlight with your back to the sun, taken from waist height. In my experience conducting the test at the same time of the day helps with the consistency.

Interesting. I do the test at waist level at the same time every day (around 5:30pm) after I get home from work, but I do it inside (same lighting every time). I have never heard of doing the test outside though. I'll have to try that. That would probably yield a lower CYA reading due to more light and thus a lower required FC level. Of course, once DST kicks in it'll be dark by the time I get home, so I'll have to go back to testing inside. Thanks for the tip though.

 

[Jezza]

Yep the test is designed to be conducted outside in full sunlight- inside lighting can really throw out the accuracy of your result. This is one result you want to try and get as right as possible as it really highlights whether you have the right FC levels.

 

[PAGirl]

How is your water circulation? Is the algae in areas away from the returns? Are your returns pointed kind of downward, or more toward the surface?

 

[Matchless1]

How is your water circulation? Is the algae in areas away from the returns? Are your returns pointed kind of downward, or more toward the surface?

Circulation is fine as far as I can tell. I have 6 returns (I purposely went overboard on this when I designed it), and the algae appears even by the returns. They are pointed very slightly up towards the surface...mostly straight horizontal and angled to one side.

 

[PAGirl]

I keep mine pointed somewhat downward, to force the water flow toward the floor. It helps circulate the chlorine better.

 

[Matchless1]

I keep mine pointed somewhat downward, to force the water flow toward the floor. It helps circulate the chlorine better.

Hmm. Makes sense. I may give that a try as well. Thanks


Sent from my iPhone using Tapatalk

 

[jblizzle]

CYA does not really fluctuate. Just use the max recent reading you got.

You also never said whether you brushed.

 

[Matchless1]

You also never said whether you brushed.

I sure did...see the last line of my second post above.

 

[kimkats]

I would do as you are thinking AND add in two more brushing in the areas you are seeing the algae trying to take hold. My guess is that those areas are not as well circulated as others due to the shape of your pool. Moving your returns and playing with the flow may be helpful. Throw some ping pong balls in to help you see the flow of your water.

Kim

 

[Matchless1]

I would do as you are thinking AND add in two more brushing in the areas you are seeing the algae trying to take hold. My guess is that those areas are not as well circulated as others due to the shape of your pool. Moving your returns and playing with the flow may be helpful. Throw some ping pong balls in to help you see the flow of your water.

Kim

Great ideas. Thanks Kim!

- - - Updated - - -

BTW, the OCLT showed 0 loss this morning (6.5 FC). I guess I'll keep an eye on the walls today and do another test tonight, but that really has me puzzled now as to whether or not these are really algae spots. Hopefully I won't get another chance to take better pictures, but if they pop back up, I'll do that and post.

 

[duraleigh]

I would take away two important things in this thread.

1. CYA DOES NOT increase in a pool unless you put CYA in the pool....period. There is no fluctuation.

2. If you see algae, brush it away and increase your chlorine level. There is no magic "tips and tricks"....chlorine kills algae. Sometimes the algae needs to be brushed up from surfaces it has been allowed to get a foothold, but the chlorine will kill it.....every time.

 

[Matchless1]

I would take away two important things in this thread.

1. CYA DOES NOT increase in a pool unless you put CYA in the pool....period. There is no fluctuation.

2. If you see algae, brush it away and increase your chlorine level. There is no magic "tips and tricks"....chlorine kills algae. Sometimes the algae needs to be brushed up from surfaces it has been allowed to get a foothold, but the chlorine will kill it.....every time.

1. That's what I thought.

2. Agreed, but I'm a little unsure at this point if I need to SLAM or not. MY OCLT was 0 last night, BUT I did brush all the spots off yesterday evening. I'm thinking I'll keep an eye on the walls today and see if they pop up again. If so, I'll leave the spots there, then do the OCLT again and see if I get a loss. If so, I'm thinking I should SLAM at that point.

 

[domct203]

....... I run a Del Ozone unit, which helps reduce chlorine usage (I’ve done my own tests and verified this), ...........

I'm curious, how did you verify that the water was still properly sanitized at these "reduced" chlorine levels?

1. That's what I thought.

2. Agreed, but I'm a little unsure at this point if I need to SLAM or not. MY OCLT was 0 last night, BUT I did brush all the spots off yesterday evening. I'm thinking I'll keep an eye on the walls today and see if they pop up again. If so, I'll leave the spots there, then do the OCLT again and see if I get a loss. If so, I'm thinking I should SLAM at that point.

Visible algae is a sign that the SLAM is needed, regardless of the OCLT result.

The first paragraph of the SLAM procedure reads:

"SLAMing your pool is the best way to eliminate algae, sanitize your pool and get your water crystal clear. If you have algae, or the CC level is above 0.5, or the free chlorine (FC) level is zero, you should SLAM the pool. You cannot do this overnight...it often takes several days to see it completed...no shortcuts. If you are maintaining proper FC levels there is no need to SLAM (or shock) weekly, or on any other regular schedule."

 

[Matchless1]

I'm curious, how did you verify that the water was still properly sanitized at these "reduced" chlorine levels?

I've kept the FC level above 3-4 the whole time (should have been higher due to CYA though...learned that mistake), as high as about 8 during non-SLAM period. My test involved simply turning off the Ozone for a few days at a time to measure the FC loss each day as well as CC. I actually found the FC loss per day to be about 2-2.5 w/o the Ozone and about 1-1.5 with the Ozone. CC levels of 0.5 were present w/o Ozone; they are 0 with Ozone. I realize the results aren't earth-shattering, but I figure, it's there...why not run it if it helps reduce FC loss. One thing to note that is that at SLAM levels (FC>18), having the Ozone on actually increases the FC loss per day. So, when I SLAM, I turn it off.

Visible algae is a sign that the SLAM is needed, regardless of the OCLT result.

The first paragraph of the SLAM procedure reads:

"SLAMing your pool is the best way to eliminate algae, sanitize your pool and get your water crystal clear. If you have algae, or the CC level is above 0.5, or the free chlorine (FC) level is zero, you should SLAM the pool. You cannot do this overnight...it often takes several days to see it completed...no shortcuts. If you are maintaining proper FC levels there is no need to SLAM (or shock) weekly, or on any other regular schedule."

Admittedly, I read this some time ago, and simply forgot about it. It just makes it a little harder to know exactly when to stop SLAMing because, the algae will go away fairly quick, but that doesn't necessarily mean I should stop right then (perhaps after one or two days). If the OCLT is 0 the whole time though, it just makes it harder to gauge the stop point. Nevertheless, SLAM is imminent.

 

[Catanzaro]

....... I run a Del Ozone unit, which helps reduce chlorine usage (I’ve done my own tests and verified this),

Dom hit this right on the nose. A SLAM is in order.

In addition, reducing chlorine consumption may not be in your best interest. My pool, roughly the size of yours with good circulation (6 returns + 2 Steps) consumed very little chlorine during the 5 months. Chemicals were about $245 for the whole season. If there was extreme heavy usage, then probably another $50.

Have you tracked the Ozone unit cost and chlorine consumption for the season (from a cost perspective)?

 

[Matchless1]

Dom hit this right on the nose. A SLAM is in order.

In addition, reducing chlorine consumption may not be in your best interest. My pool, roughly the size of yours with good circulation (6 returns + 2 Steps) consumed very little chlorine during the 5 months. Chemicals were about $245 for the whole season. If there was extreme heavy usage, then probably another $50.

Have you tracked the Ozone unit cost and chlorine consumption for the season (from a cost perspective)?

I have not. The pool is brand new (7/4/16 was first swim day), so I haven't had a chance to see how long the Ozone unit will last. When it's time to replace though, I'll definitely compare the two along with the energy cost to run the Ozone unit, which I'm sure is minimal, but I'll throw an amp meter on it anyway just to see.