First year owner, mustard algae, I'm a convert to the TFPC

[kfinke]

View attachment 68526Bought a new house this May, pretty much because we've always wanted a pool. Both grew up with them, but we were kids and never did more that simple chores. Finally, we have our own, and it's a beauty! The previous owner built the house and pool, and taught us everything she knew and left us with a ton a chemicals. She gave us the run down on testing with strips, adding chlorine tabs to the chlorinator, and shocking from time to time. Said she occasionally had yellow algae, and threw in some Yellow Out.

So, we take over the pool. She had it opened and setup, all seemed perfect. I shocked with some liquid shock from time to time and dropped some tabs in the chlorinator. Learned to vacuum. Fixed the Aquabot and used him a few times. All is grand. Use test strips like every other day, and take my water to Leslie's. All seems well, water is perfect according to them.

About 6 weeks ago, had some yellow stuff that covered the bottom and the hills of the deep end. Wasn't sure what it was. Tossed in some yellow out (probably only like half a pound) and shocked. Went away. Man, this pool stuff is easy!

Last Friday (9 days ago) yellow returned. Vacuumed. Shocked. By Tuesday, completely back. So, I vacuum again. This time I stir it up. Pool turns green and cloudy! Oh no, so I rush to Leslie's. They tell me chemistry is Ok, but the yellow algae requires 5.1lbs of Yellow Out, followed by shock every 12 hours for 36 hours. I diligently do so. Still saw traces of yellow, so I shock one more time.

By this point, I'm voraciously reading on the internet. Here, the pool forum, whatever I can find about yellow algae. Really starting to learn the pool chem, and really understanding how in trouble I might be. Bought the Leslie's version of the Taylor test kit. (I realize now I'm missing the good FC/CC test FAS/DPD. I ordered the Taylor kit for just that online today. The numbers below are from the other test in the Taylor kit.) I stop in a different pool store. He tells me CYA is fine (I suspect over 100) and tells me to add more tabs straight to the skimmers. I do. Also says to treat again with yellow out and more shock. I do. Had pool floats and toys in the shock. Bleached some parts. I did all of this on Saturday, and my Aquabot was cleaning the pool. Woke up Sunday to near perfect looking conditions. Blue, almost perfectly clear. No sign of algae. Not sure if that's the Aquabot or if it's gone. We took him out and enjoyed the pool on Sunday.

But, this morning -- Monday -- I noticed traces of the yellow back in the usual spots. I guess it's time for some numbers:

	Me	Leslie's
FC	7.5-15	10
TC	5-10	10
CH		190
CYA	140	95
TA	90	90
pH	7.4	7.5
Copper		0
Iron		0
TDS		1400
Pho		0

I should note that while all summer I had been learning some things about pool chem, I never really suspected things were bad. Most of the summer, Leslie's reported my CYA at 50-60. My own test strips seemed Ok. But, after trying to treat for the mustard algae with bleach and powder shock and tabs, my CYA seems to have jumped to over 100 in a short period of time. I can read, and now I know just how bad this might really be and why I can't seem to rid the pool of the yellow monster.

So, it's late August. And it has been a cool summer, with not much sign of a warm temps to come. It's our first year with the pool, and I'm going to keep it open as long as we can stand the temps. Hopefully there's another round of mid 80's in our future and some pleasant swimming! But, at this point I don't know what to do. I can follow the math and read charts, and if my CYA is really where I think it is, then killing the algae with chlorine seems difficult. I know in a few weeks I'll be draining a foot of water to close the pool, but it's my understanding that it's anyone's guess if your CYA diminishes over the winter or not. I'm considering the bio-active product to reduce the CYA, but they claim 5 FC, and I'm not sure I can get there without the algae just taking over and finishing the swimming season with a green pool. In OH, I realistically can drain and fill for reasonable $$$, so I was thinking about a few 6in water changes. If I changed say 40% of the water, I'd be in the 70-80 range. The winter drain would probably take care of the rest.

So, do I drain water? How effective will winter be at CYA reduction and killing the algae?
I assume I should stop using tabs all together?
Is there anything else I should do for the algae now with a few weeks left?

Hoping to go BBB/TFPC next year and be in control!

 

[JVTrain]

Welcome to TFP!

I would drain as much as you can in a single drain before closing, even now if you think your swimming season is about done. Leave only 1 foot of water in the shallowest part of the pool as the maximum you can do at one time. In order to reach a manageable CYA level from your 140 ppm, you need to drain roughly 60% of your pool volume. Then you can close the pool clean, with a better chance of opening to a clean pool in the spring.

I would certainly discontinue regular usage of chlorine tabs. They can be handy when you're gone for several days as a supplement, but they can put you in a world of problems when used continuously. Liquid chlorine or upgrading the a salt water chlorine generator are the best long term options. Calcium hypochlorite can also be used occasionally for dosing or when you SLAM the pool as long as you fully understand that this chemical will also raise your CH level. Not a big deal for vinyl pools but still can be a problem if it gets too high (scaling, etc.).

For now, you could limp your pool along with marginal water conditions for a few weeks because it's not realistic to hope to clear the pool with a CYA level at 140. Using more yellow out can help clear a pool, but creates a massive chlorine demand as a result. It's essentially adding ammonia and a weak algaecide to your pool to form monochloramine (combined chlorine). Once the monochloramine is consumed, residual ammonia continues to consume chlorine until it's exhausted. It's a band aid on deep wound that gets ripped off after a day or so. The pool will look better for a little while, but likely will get worse in short order.

Before closing you should drain in a single large drain for sure. 6 inch increments are the slowest and most water wasteful methods to reduce CYA. You'll use twice as much water and time as you would on a single drain to get the same result. Once you have completed and get your CYA level at 60 ppm or south of that, then SLAM the pool to pass the criteria, using liquid shock aka bleach before closing. You want to close clear and sanitized so that you can open to a clean pool in the spring. DO NOT close until your water is 60 degrees or less. This will likely be into October. It's a long time to maintain sanitation, but as the water cools, chlorine demands is much less and leaving the cover off at night, only running pump at night, etc can help speed the cooling process. Forget bioactive as well. We've had some first hand testing results reported here and results were marginal at best, low CYA reductions or none at all. Not worth the cost.
Bio-Active CYA Reducer trial - Page 3
Underwhelmed by Bio-Active CYA reducer
Bio Active Results


That's a lot to take in, but it's a start. Make sure you've read through the ABCs, CYA/Chlorine chart and SLAM procedure in Pool School!

 

[kfinke]

Thanks for the reply! I'm reading everything I can!

So are you suggesting that I do a water drain now, with a few weeks left, and then another at close? I know at close I drain below the inlets, so that's a decent drain. I'm not sure why the 6in method is worse -- can you explain that? I thought that if I drained 10% of the water, then CYA would go down by 10%. Is that not true? I'm frankly surprised my CYA rose from the numbers Leslie's was giving me. They claimed like 50 or 60 all summer, and then poof I was at like 100 or more! I used tablets for sure, but not really many more than I had been using, like say 6 a week. The Power Powder Plus doesn't have it as far as I understand, it's just cal-hypo, right? Finally, what do you think will happen to my CYA over the winter?

 

[JVTrain]

Because the meaningful swimming season is nearly over for us in the northern climes, I'd suggest limping along with suspect water (a couple weeks?) and maintaining a high FC until you're ready to close, or a several weeks before you close. Knowing how long you want to stay open would possibly change my opinion. A couple weeks? Then limp it along, then attack CYA and algae fairly soon. Another month or more, then it may be worth it to do the big drain now, then refill and SLAM right now. However, this means a sharp drop in temperature refilling with cold water and essentially would close your season anyway. I wouldn't try to limp it along for too much longer...

Right now your CYA is 140. This means to maintain sanitation, without algae present, you would need to maintain a MINIMUM of 11 ppm FC. Your target level to dose up to would be 16 ppm. You should maintain this until your ready to drain, SLAM, then close. You can still use the pool, provided you maintain these levels and you can still see the bottom for safety. Use liquid chlorine only as you don't want to raise that CYA any more. Powder plus is indeed cal-hypo, if it's from Leslies. Can use it, but again, know that you're raising your CH "permanently" as well, but will also go down with draining. To eliminate algae at 140 ppm CYA, you'd need to target, then maintain 56 ppm FC until the pool was clear, 0 CC, etc. Not practical. Live with algae short term, while maintaining adequate sanitation, 11-16 ppm FC, then big drain, big refill, SLAM before closing.

The reason that 10% drains are less effective is that when you drain, your CYA goes to 126 when you refill. Then when you drain 10% again, fill, your CYA goes to 113. Repeat and you get 102, Repeat and you get 92 ppm. You've replaced 40% of your water. What would have happened if you did 40% in one go? Your CYA would have gone to 84 ppm. You're diluting your potential drain every time you refill on partial drains. One large drain is always more effective than several smaller ones.

CYA results from Leslie's are terrible, much like the rest of their results. With tablet use, your CYA will climb slowly and steadily over time. Each tablet adds a defined amount of CYA.

Over the winter, provided you close clean at 60 degrees or less, elevate to shock level and cover, your CYA won't change, until you refill and dilute slightly. However, if you do not close clean and timely, CYA can be consumed by bacteria in some cases. This usually turns CYA into ammonia. Ammonia has a large chlorine demand. 3 ppm of chlorine to eliminate 1 ppm of ammonia. Not something I would risk over the winter when you have 140 ppm potential ammonia in the pool.

 

[kfinke]

I understand. I figured out the math on the water drain after I replied, lol. So, the right idea is to wait until close, drain MORE than needed for closing. Fill back up to close level and then SLAM? Or fill to normal level, SLAM, and then drain to close level?

 

[kfinke]

I think I answered my own question. In order to SLAM, I'd be running the filter until I pass the test. So, I'd drain 60%, refill to operating level. SLAM. Once I pass, drain to close level and close. Right?

 

[JVTrain]

Yep. That'd be the way to go. Only need to fill enough for the SLAM to make sure your skimmers can run, 2 inches or so above the bottom of the opening. Then not so much to drain after. The bonus of doing the SLAM right before closing is that, FC losses will be less due to less sunlight, lower temps and low/no usage. Plus once you pass the OCLT you can close right after that at since your FC is at shock level, provided your water is 60 degrees. Just a little chilly out for pool work.