Algae Problem?

[scooper]

New member (although I've visited the site quite a bit for a couple years) and I'm wondering if I have an algae problem or something else? I had the pool opened a week ago and found murky, greenish water. It was tough to see the bottom of the deep end. I've had algae problems a few times over the last couple years so I assumed it was back. The guy who opened my pool put 4 pounds of non-chlorine shock in (which I knew would do nothing, but let him do it anyway). I didn't have time to SLAM it properly until Tuesday, so I didn't mess with it until then. Check the specs in my signature.

I tested the water Tuesday morning and here is what the numbers were:

FC = 1.5
CC = 2.5
CYA = 10
TA = 130
pH = 7.6

I also had the water tested at my local pool store which confirmed my numbers and also showed that the CH was 320 and phosphates were 0.

So... very little FC, CYA was way too low and TA was high. From reading on the site, I decided to tackle the algae first and start SLAMing the pool. I did add a gallon of liquid stabilizer to bring the CYA level up to about 25 (which still isn't good, I know). I started SLAMing and got my FC to 11 pretty quickly. I checked my FC levels every 1-2 hours, adding bleach when needed, which was just about every time until evening. I also had my SWG on super-chlorinate the whole time. For the OCLT test Tuesday night, I tuned off the SWG and tested about an hour later. The numbers for that were FC = 11.5, CC = 1.5. The morning numbers were FC = 10.5, CC = 1.0, so petty good, right? Except the water was still murky and greenish (although not quite as bad as the day before).

I turned the SWG back on (super-chlorinate), poured in another gallon of liquid stabilizer to bring the CYA level up to about 38 and added bleach to bring the FC up to 15. I checked my FC levels every 1-2 hours, but didn't need to add bleach the rest of the day. The FC level actually went up to 21 at one point so I took the SWG off super-chlorinate and lowered the output. For the OCLT test last night, the numbers were FC = 16, CC = 1.0. The numbers this morning were FC = 15, CC = .5, so really good, right? Except the water, while quite a bit clearer, was still murky and still a little greenish.

So am I being impatient or is there something else going on? Should I keep SLAMing the pool? When I've SLAMed the pool in the past, the water cleared up right away (much faster than I was able to keep the FC levels up and pass the OCLT test). Complicating matters is that since I've been testing so much over the past few days, I'm now out of FAS/DPD testing powder and drops and can't get any more delivered until Saturday.

Any ideas or advice?

 

[JVTrain]

Keep after it is the best advice. Going to have to wait for your reagent to keep tackling it properly.

Is your SWG off during the OCLT? It needs to be OFF and there's no sense running it during a SLAM anyway, just add bleach and save your SWG cell.

Thanks for finally posting and good luck!

 

[scooper]

Yeah, I've turned off the SWG each night about an hour before the OCLT and kept it off until after the morning test, but you're right, I might as well keep it off all the time while SLAMing. Thanks for the tip!

Keep after it is the best advice. Going to have to wait for your reagent to keep tackling it properly.

Is your SWG off during the OCLT? It needs to be OFF and there's no sense running it during a SLAM anyway, just add bleach and save your SWG cell.

Thanks for finally posting and good luck!

 

[scooper]

I just tracked my FAS/DPD reagent refill shipping and it won't be here until Monday. Is there any other way I can test for shock level FC? The water looks much, much better this morning — almost clear, but I'd still like to know what my FC level is and keep SLAMing until it's completely clear.

 

[Patrick_B]

Not above 10 PPM FC.

What was your last addition to get you from x to y level of FC?

 

[scooper]

The last time I was able to use my FAS/DPD kit to measure (yesterday morning), the FC was 15. I added a gallon of liquid stabilizer to get the CYA level up to around 52 and then, using the Pool Math page to calculate, added two gallons of 7.85% bleach to bring the FC up to 21. Since then, unfortunately, I've just been guessing. I did have an OTO test kit and found a thread here that's been helping me at least make somewhat educated guesses.

 

[Patrick_B]

Ok,

May I ask why you increased the Cya?

 

[scooper]

Because it was so low (10) at opening, especially for a SWG pool, that I've slowly been adding liquid stabilizer over the last few days to get it to a more acceptable level. I'm going keep adding over the next few days to get the 70-80 range that's needed. I just decided to do it over a number of days while I'm fighting the algae to keep my bleach bill down a little.

 

[scooper]

Okay — I just got my FAS/DPD reagents in and tested the water. Apparently my "educated guesses" were a little off (big surprise, huh?) and my FC is really high. Here's what the numbers are now...

FC = 37
CC = 1
CYA = 53

The water is perfectly clear now, so I'm hoping the algae is dead after being SLAMed for a week. I'll do an OCLT test tonight and see what that shows.

My kids are really anxious to swim, though, so (if the algae's dead) what should my FC be before they can dive in? And what's the best way to get that number down?

 

[chem geek]

Anything below SLAM level which with a 53 ppm CYA would be around 40% of that or 21 ppm FC would be OK. Exposing the pool to sunlight is the easiest way to get the FC to drop. If you want it to drop faster, then you can add a dechlorinator -- the least expensive with fewest side effects would be hydrogen peroxide which you can get in Baquacil Oxidizer which is 27% hydrogen peroxide. You put in 1/9th the amount in volume equivalent to 6% chlorine. So to drop the FC from 37 ppm to say 10 ppm in 27,000 gallons you'd add 168 fluid ounces (1.3 gallons).

 

[scooper]

Thanks for the Baquacil Oxidizer tip. Before I try it, though, I want to be sure the algae is gone. The water passed the OCLT test this morning and looks clear, but I'm a little concerned that my CC level is still 1 (and not 0-.5). The guy who opened the pool about a week and a half ago put in four pounds of non-chlorine shock and I've read that can cause false CC readings — but could that be cause after that many days? Or do I still have living algae? Or something else?

Anything below SLAM level which with a 53 ppm CYA would be around 40% of that or 21 ppm FC would be OK. Exposing the pool to sunlight is the easiest way to get the FC to drop. If you want it to drop faster, then you can add a dechlorinator -- the least expensive with fewest side effects would be hydrogen peroxide which you can get in Baquacil Oxidizer which is 27% hydrogen peroxide. You put in 1/9th the amount in volume equivalent to 6% chlorine. So to drop the FC from 37 ppm to say 10 ppm in 27,000 gallons you'd add 168 fluid ounces (1.3 gallons).

 

[chem geek]

Yes, the non-chlorine shock could still be there and registering as CC. It goes away slowly if there's not a lot around to oxidize. I doubt the CC is algae. If your overnight chlorine loss rate is low and the water is clear and you don't smell anything bad, then the CC is likely a false or innocuous reading. Up to you if you want to continue with the elevated chlorine. You could just let it drop more slowly from sunlight. That's the easiest and least expensive thing to do.

 

[scooper]

Thanks for the advice and reassurance. The water passed the OCLT test again this morning and the CC level was down to .5, so it looks like everything's good. I put in a gallon of Baquacil Oxidizer this evening to help bring the chlorine level down (it's been nothing but clouds and rain the last two days) and I'll check and see where the levels are tomorrow. Thanks to everyone for the help!

Yes, the non-chlorine shock could still be there and registering as CC. It goes away slowly if there's not a lot around to oxidize. I doubt the CC is algae. If your overnight chlorine loss rate is low and the water is clear and you don't smell anything bad, then the CC is likely a false or innocuous reading. Up to you if you want to continue with the elevated chlorine. You could just let it drop more slowly from sunlight. That's the easiest and least expensive thing to do.

 

[scooper]

Okay, new problem now. Wednesday evening I put in a gallon of Baquacil Oxidizer to bring the FC level down from 32 to a reasonable level. When I measured the FC Thursday morning, it was 1.5 (and my CC level was up to 1.5). So I turned my SWG back on (set at about 70% output) and, using the PoolMath page, added bleach to bring the FC level up to 6 (the CYA level is at 80 now). The pool was closed all day yesterday. But when I tested again this morning (Friday), my FC level was only 2 (the CC level was down to 1). So is the Baquacil Oxidizer still consuming the FC or giving me a false reading somehow? Should I increase my SWG output and keep adding bleach?

 

[pooldv]

I don't know anything about baquacil. But, I do know that you need to keep the FC level above the minimum for your CYA at all times or algae will start growing. Definitely increase SWG and/or add bleach until FC stabilizes.

 

[chem geek]

Baquacil Oxidizer is hydrogen peroxide and should react fairly fast with the chlorine so I suspect it just wasn't completely mixed. Just keep monitoring and if the FC is still dropping then add some more bleach. It should get back to normal very soon.

 

[scooper]

I put the Baquacil Oxidizer in to bring the FC level down at chem geek's suggestion. By my calculations (using the PoolMath page), one gallon should have only dropped it from 32 to 14, so getting these low FC numbers is puzzling to me. I've added more bleach and increased my SWG output, so we'll see what happens.

I don't know anything about baquacil. But, I do know that you need to keep the FC level above the minimum for your CYA at all times or algae will start growing. Definitely increase SWG and/or add bleach until FC stabilizes.

- - - Updated - - -

Thanks - I'll keep on it. Hope it didn't sound like I was throwing you under the bus in my reply to pooldv. I appreciate your help.

Baquacil Oxidizer is hydrogen peroxide and should react fairly fast with the chlorine so I suspect it just wasn't completely mixed. Just keep monitoring and if the FC is still dropping then add some more bleach. It should get back to normal very soon.

 

[chem geek]

One gallon of Baquacil Oxidizer which is 27% hydrogen peroxide in 27,000 gallons should have the same effect as removing the chlorine equivalent of 9 gallons of 6% bleach which would be a reduction of 20.6 ppm FC (give or take).

You are sure you got Baquacil Oxidizer and not Baquacil CDX, right? Keep us posted with how it goes.

 

[scooper]

Yes, it was Baquacil Oxidizer. I added a gallon of bleach and put my SWG on 100% output this morning, then tested it a few hours ago. The FC was 5.5 and the CC was 1, so I'll see how this holds up.

One gallon of Baquacil Oxidizer which is 27% hydrogen peroxide in 27,000 gallons should have the same effect as removing the chlorine equivalent of 9 gallons of 6% bleach which would be a reduction of 20.6 ppm FC (give or take).

You are sure you got Baquacil Oxidizer and not Baquacil CDX, right? Keep us posted with how it goes.