Running out of POP!

Hello all,
I have a 15,000 gallon in ground pool that I opened 3 weeks ago. Holy swamp!!! I have been a longterm lurker at this forum (as in years) and follow the BBB method. I raised my CL to 20 and it 3 days had sky-blue but extremely cloudy water. I couldn't see the first step. I held the Cl and let the filter go for about a week . Now I could see the 1st step but no others. I took apart the filter, and it checked out....I flushed it with a hose and put back together. Sand was replaced last year. I have let the filter run 24/7 for the past 2 weeks while maintaining a free cl of 20. The water is not budging. It is extremely cloudy. For the past week I have been adding about a cup of slurried DE to through the skimmer with minimal results.

The pool is holding CL level overnight, so I think that all the algae is dead.

Current test results
CYA 40
Total cl 20
combined cl 20
ph 7.9
Alk 125

Borates are 15 but are from pool store test, as I don't have a borate test.

I have a SWG but have left it off during this process. I have a 3/4 hp pump on a tagelus 50 (200lbs sand) filter, so I don't think the pump is oversized, but I may be wrong! Is there anything else I can do to speed the process??

Thanks!!!

Are you sure those test results are correct? How are you testing?

Because, if CC=20 and TC=20, then FC=0 which means you have NO free chlorine.

Oops, sorry. FC and TC are 20 CC has been no more than 0.5 for last 2.5 weeks. pH I use a probe for aquariums...it's been calibrated recently. I test cl- using a FAS-DPD titration method; CYA, alkalinity, and acid demand I usually do at work (university lab). I have also confirmed cl- & pH levels at work. I am beginning to think that I'm missing something, or my filter is sick.

Thanks,
Stella

Yes, if you want to try something, add another dose of bleach and then turn your filter off. I want to leave it off for 2 full days.

Here's what I think may be happening. The Tagelus 50 is a shallow bed 21" sand filter. It's rated at 50gpm, but in reality, should never exceed 35 GPM. I'm not sure what 3/4HP pump you have, but if it's something like a Pentair Challenger 3/4HP . . . you're probably running around 60 GPM, or nearly double the never-exceed rate.

There's a LOT of back-story on this that I can't go into right now. But what I'm beginning to suspect is that blowing dead algae THROUGH a sand filter actually breaks the algae particles into even finer particles . . . and that after they've been broken, they not only cannot be filtered with sand filters, they are difficult to filter even with cartridge or DE filters.

There are two sorts of solutions here: preventative and curative.

+ To prevent this problem in the future, we need to make sure flow through your system NEVER exceeds 35 GPM, except when you are backwashing, and that it never exceeds 45 GPM even then.

+ But, to cure the problem, we've got to find a way to get the algae out BESIDES filtering . . . because if I'm right about all this . . . you can't filter it, now that the high rate flow through the sand has shattered the algae particles.

So, I want to try this
1. Make sure your chlorine is 20 or more this evening, and that there is NO live algae left.
2. If so, turn your pump OFF, and leave it off.
3. Check chlorine levels tomorrow PM, and make sure they are 10+ . If not, add a gallon of plain 6% household bleach.
4. Check Monday am, and see if there has been any change. Let me know what you see.

This sounds exactly like what is happening with my pool, except that I have a 1-HP pump and a 300# tagelus sand filter. Water color is good, chlorine levels are holding, all other chemistry looks good, water just won't clear.

Ben do you think turning off the filter will let the particles settle?

Quote:

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Originally Posted by TheGoose

Ben do you think turning off the filter will let the particles settle?

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I don't know. I'm going to be recommending a 3-stage trial:

1. Try to settle with nothing. Vacuum to waste if it works.
2. Add floc, and try to settle. Again, vacuum to waste if it works.
3. Add clarifier, and try again.

During the recirculation steps (2 & 3) it will be important to bypass the filter. I do know that sand filters can 'break' floc agglomerations.

Thanks!! The pump is a Hayward SuperPump if that helps any. I just checked and adjusted the cl- to 20; it was between 15 and 20. I'm going to let it circulate for another half-hour and shut off the pump. I agree that the dead algae is going right through the filter. The first few days I was needing to backwash every few hours; now the pressure rises maybe 1-2 psi over the course of the day..even with the DE added. I will report back with results on your recommendations. Once again, thank you so much.
Stella

Yeah. A 3/4HP Super Pump is almost certainly over-driving a Tagelus 50D, which shouldn't be run at more than 35 GPM max. If you have an up-rate Super, you're probably running 40 - 50 GPM.

Tell me what your clean filter pressure is, and I can estimate it more accurately.

Clean pressure hovers between 11 psi & 12 psi. When I restart pump, I can check that against another gauge. Thanks!

That would suggest you are running between 40 and 50 GPM if the pump is an SP2605x7, or between 50 and 65 GPM if it's a SP2607x10 . . .

Ok, so I walk out this morning....cloudiness is about the same. There may be a very slight difference, or it may be my eyes being optimistic. As to the pump, the model # C48J2N131B1 and the motor # SP-1605-Z1-M Service: 1.0.

I was thinking of taking a bucket of the pool water and adding floc to that (as a trial) before adding to my pool, to see if it would settle in the bucket.

I did some experimenting today. I hauled about 10, 5 gallon buckets to work with me. I work with fish. I filled 3 five gallon aquariums with my water, and hooked up a mini sand, DE, and cartridge filter. After about 6 hours, the DE had started to clear the water; the sand and cartridge will probably still be the same a month from now!. I tried a few different polymer pool flocs. I used one beaker with nothing added as a control, none of them did a thing. I had cultured for algae last week (just in case I hadn't shocked it into oblivion)...no algae in the pool water (or there wasn't last Wednesday, and I have maintained same cl level). I don't know if any of this will help. Is there a chance that an alum based floc would work?? I couldn't get my hands on any today.

Quote:

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Originally Posted by sosspenc

Is there a chance that an alum based floc would work??

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Yes, but as you probably know, alum is 'twitchy' -- you have to get your CA high and your pH low (by pool standards) for optimal results with most particles. Polyaluminum chloride is more effective and less twitchy. I'd found some on Amazon, but it's not available, but I did some more looking and found that GLB Drop-n-Vac is an alum and PAC blend. You may want to try that:
GLB Pool & Spa Products 71408 1-Quart Drop n' Vac Pool Water Clarifier @ Amazon

I would recommend a jar test, first.

I'm trying to find some plain, high concentration PAC, but I'm not having a lot of luck.

Thanks for the link! It will ship out tomorrow or Wednesday; wasn't eligible for overnight for some reason...oh well. I've found some alum; gonna jar test that in the morning...should know something by tomorrow afternoon. Fingers crossed. I added half a dose of muriatic acid tonight to lower pH some...just in case the alum works. (pH -7.8) I am aiming for 6.9 -7.0. My alk is around 120 right now. Ca+ is around 200 ( I will get a definitive number tomorrow, very rarely test ); what would you recommend I target for Ca+? I know I need a sizable alkalinity buffer so the floc can hopefully work it's coagulating, floccing, and settling magic.

Well, alum will probably work if you tweak it, and it definitely sounds like you know enough to know how to do so. PAC is just easier and more effective. I think the critical elements are pH in the 6.5 - 7.0 range, and sufficient alkalinity to buffer it, as the floc forms. Sorry, but I don't have time to look it up now -- traffic on the site has gone crazy!

Just an update...I found the ProTeam super floc locally. I am at home today so didn't have fancy equipment. I bucket tested both granular alum and the ProTeam stuff. ProTeam made tiny, tiny flocs after about an hour, but they were having difficulty settling. Alum turned the bucket water VERY cloudy for about 10 minutes ( I panicked even though it was just a bucket, lol); when this dissipated, I could see 1/4 inch to maybe 1/2 inch flocks forming in addition to a fine precipitate. My alum bucket settled in about 90 minutes. The PAC is still struggling to settle, I am not sure if they are going to be able to do so, as they are barely visible....I may have miscalculated the dose...the instructions were vague, and of course the MSDS says "proprietary" and lists no concentration! Both products went into the bucket at 8 am.

At noon I decided to go ahead with the granular alum. I half dissolved it and dumped it into my pool. Let the filter rein in recirculate for about 2 hours. I just checked and it is settling fast!!!. I used 10 lbs of Leslies in 15k of water. pH was 6.9, alk 120 and Ca+-400. I will let you know how the PAC does overnight. Thanks for your help!!!!!!!!

Stella

Thanks for the info, Stella.