Algae problem or filter problem?

[FredFredrickson]

Hi all. I struggled with a SLAM getting much of anything done last month with my crappy Intex paper filter so we recently switched to a sand filter and our pool is no longer cloudy and our overnight chlorine tests were dropping less than 1ppm overnight, so we stopped with 12 FC.

But now every day, the water is crystal clear and blue, but there's still some sediment on the bottom of the pool that, if brushed, turns into a slightly green cloud, and it will make the pool mildly cloudy (not terrible but noticable) if you brush the entire thing.

I keep vacuuming but due to water constraints in my area we are unable to vacuum to waste. I vacuum every other day and brush daily and it keeps coming back.

The CC is zero.
CYA 30
pH 7.4
FC stays between 3-6 but usually over 4
TA 80

Am I experiencing new algae, should I raise FC to slam levels? Or am I just seeing the same stuff resettle?

 

[Texas Splash]

but there's still some sediment on the bottom of the pool that, if brushed, turns into a slightly green cloud, and it will make the pool cloudy

Oh boy, that sounds like algae. Are you sure you passed all 3 SLAM criteria before? Have you tried to capture any of it with your fingers to see if it has any texture or if it's slimy? Sometimes you can pinch it between your thumb and middle finger to get a better look. Has the filter pressure been increasing as well?

 

[PoolStored]

Your filter will filter out dead algae. You likely have live algae. In my pool, if I even "sniff" minimums, I get some haze in the pool. Your pool will consume FC every day, which can also be variable. My guess is that you got to minimums and have algae again. It is better to run on the high end of the recommended range, 6 in your case, to have enough FC to handle a high FC demand day (sun, swimmers etc.) I can lose 5.5FC a day with sun and swimmers, my min is 4 and I run my pool at 9FC.

I would slam. I would also ask if you removed the stairs and scrubbed them? Sometimes we can miss areas that harbor algae and still pass slam, allowing it to re-take hold.

 

[FredFredrickson]

Oh boy, that sounds like algae. Are you sure you passed all 3 SLAM criteria before? Have you tried to capture any of it with your fingers to see if it has any texture or if it's slimy? Sometimes you can pinch it between your thumb and middle finger to get a better look. Has the filter pressure been increasing as well?

I can't touch it. If you get near it, it immediately disappears into a small cloud. Filter pressure is very near it's starting pressure, I backwashed last week. It does increase after I vacuum.

Your filter will filter out dead algae. You likely have live algae. In my pool, if I even "sniff" minimums, I get some haze in the pool. Your pool will consume FC every day, which can also be variable. My guess is that you got to minimums and have algae again. It is better to run on the high end of the recommended range, 6 in your case, to have enough FC to handle a high FC demand day (sun, swimmers etc.) I can lose 5.5FC a day with sun and swimmers, my min is 4 and I run my pool at 9FC.

I would slam. I would also ask if you removed the stairs and scrubbed them? Sometimes we can miss areas that harbor algae and still pass slam, allowing it to re-take hold.

We keep the stairs out unless the pool is in use. I have washed them but the sediment comes back during days we don't even put the stairs in.

I have yet to test below 3 PPM even once, and I always test before adding chlorine. Our pool is in a shady area (trees might be part of the problem) and we keep a solar cover on when not in use so really I'm only dropping 1-2 ppm a day at 70-75 degrees F water, when nobody is swimming.

I'm going to increase the FC to Slam levels for the week as we continue vacuuming and brushing.

As I understand it, SLAM levels are still safe to swim in?

 

[PoolStored]

As I understand it, SLAM levels are still safe to swim in?

Yep, if you can see the bottom.

As to the minimums, as I said, if I even "sniff" minimums (even off by 1ppm), I'll get haze. Even the accuracy of your test could be off. My brother and I did a "test challenge." He tested and I tested. We watched each other. We were 1ppm apart. I've seen it here dozens of times where people swear they didn't hit minimums. I'm one of them. It happens, even if you can't explain it.

I still recommend that you stay at the high end of the recommended range, 6+, and you will likely avoid another outbreak.

I'm only dropping 1-2 ppm a day at 70-75 degrees F water, when nobody is swimming.

That sounds about right, mine is the same with cover, no swimmers.

 

[PoolStored]

It does increase after I vacuum.

Do you vacuum to filter or waste? Do you backwash after you vacuum if you vacuum to filter?

 

[FredFredrickson]

Do you vacuum to filter or waste? Do you backwash after you vacuum if you vacuum to filter?

Yeah I can see the bottom no problem. The water is clear until I brush or we swim. After that it only gets a little cloudy, you can still see the bottom but it loses the sparkle.

I vacuum to filter because we can't easily refill. I have been backwashing when the pressure gets close to 25% above baseline. Should I backwash every time I vacuum?

 

[PoolStored]

I vacuum to filter because we can't easily refill. I have been backwashing when the pressure gets close to 25% above baseline. Should I backwash every time I vacuum?

I don't see how backwashing after vacuuming to filter would actually help. Filter should filter dead algae. Won't filter live.

Not sure how it could NOT be algae. A filter will filter dead algae and would not put it back into the pool. Even if you vacuumed to filter and DIDN'T backwash, should not return it to the pool.

Why don't you do an OCLT tonight? Go test now and again before sunrise. This will give us the best sense.

 

[FredFredrickson]

I don't see how backwashing after vacuuming to filter would actually help. Filter should filter dead algae. Won't filter live.

Not sure how it could NOT be algae. A filter will filter dead algae and would not put it back into the pool. Even if you vacuumed to filter and DIDN'T backwash, should not return it to the pool.

Why don't you do an OCLT tonight? Go test now and again before sunrise. This will give us the best sense.

Unfortunately it's at my in-laws so I didn't have a chance to get an OCLT last night, I'll try tonight. Though that said, we have passed OCLT in the past week with the sediment present. So I'm not sure if it's live algae. Maybe it is but only a tiny bit. It settles on the floor in little clumps until you brush / vacuum.

I'm bringing the chlorine up to SLAM levels this morning and I'm running low on my FAS-DPD so I ordered a new one to come in tomorrow.

Which leads me to a question- what's the behavior of this test if it expires? I haven't had the FAS-DPD for a full year yet, so I don't think it's expired, but is it possible my readings are incorrect? This is the replacement kit I keep getting for my K-2006. https://www.amazon.com/dp/B00QRI2UCA

I also had to re-order CYA test because i burn through those quickly. https://www.amazon.com/gp/product/B07G5FSHBX/

 

[Texas Splash]

I haven't had the FAS-DPD for a full year yet, so I don't think it's expired,

If the products were stored in a cool/dry location, they should be fine. The FAS-DPD you see on Amazon is fine as well.

 

[Newdude]

Keep in mind with your testing, it is merely a momentary snapshot of that one pint (?) of your 5k gallons. Above ground pools are notorious for poor circulation and no matter where the sun is in the sky, there is a shaded wall and a blazing sunshine wall.

Any pool, even with good circulation, may be considerably off from one area to another. The closer you see a test come to minimum, the likelier it is that there are spots at or below minimum at that time, typically a day after you dosed last. Immediately after you dosed, it matters less if one area is 2 PPM low when it's still 4PPM+ above minimum.

 

[FredFredrickson]

Keep in mind with your testing, it is merely a momentary snapshot of that one pint (?) of your 5k gallons. Above ground pools are notorious for poor circulation and no matter where the sun is in the sky, there is a shaded wall and a blazing sunshine wall.

Any pool, even with good circulation, may be considerably off from one area to another. The closer you see a test come to minimum, the likelier it is that there are spots at or below minimum at that time, typically a day after you dosed last. Immediately after you dosed, it matters less if one area is 2 PPM low when it's still 4PPM+ above minimum.

Gotcha. Gonna keep it higher.

 

[FredFredrickson]

Keep in mind with your testing, it is merely a momentary snapshot of that one pint (?) of your 5k gallons. Above ground pools are notorious for poor circulation and no matter where the sun is in the sky, there is a shaded wall and a blazing sunshine wall.

Any pool, even with good circulation, may be considerably off from one area to another. The closer you see a test come to minimum, the likelier it is that there are spots at or below minimum at that time, typically a day after you dosed last. Immediately after you dosed, it matters less if one area is 2 PPM low when it's still 4PPM+ above minimum.

I wanted to update everybody on the progress.

I brought chlorine levels up to SLAM levels for a full week, and although we were not failing OCLT, I did start to notice less green at the bottom.

After that, for the last ~3 weeks, I've been keeping Chlorine levels around 10-13 (40 CYA now) the problem is far less common but every day I brush or vaccum, and there's still a hint of green dust at the bottom of the pool, in some places but not others.

When we open the pool it's crystal clear but after swimming it gets a bit cloudy (not overwhelmingly - still see the bottom no problem, and the water stays blue, but it loses sparkle).

I have come to the following conclusions:

1. The nearby pine tree is dropping too much stuff into the pool.
2. Bad circulation in the above ground pool benefits from keeping chlorine much higher than the target range.
3. The filter works but the stuff in the pool settles too quickly for the filter to get it all day.

All in all, it's completely workable and not an issue. Of course, the perfectionist in me hates that I can't eliminate the problem altogether, I think we're probably in good shape as far as things I can control.

Unless anybody has any other ideas.

 

[Texas Splash]

Those items you noted above can certainly be challenging for a simple AGP. As long as you're happy we're happy.