CurtisT Posted June 15, 2009 Report Share Posted June 15, 2009 I've been fighting a problem with what I assume is yellow algae in our pool since about February. Here are the stats on the pool... Size: ~18000 gallons Type: Gunite w/ Pebble Tec finish Chlorine using tri-chlor tabs Location: Houston, TX Filter - cartridge (cleaning about every 3 weeks right now) pH - 7.6 - have actually had to work to keep the pH up this year using Borax. Alkalinity - 110 CYA - 80-150 (depending on which store... my test shows over 100 which is the highest it will read). Cl - .2 ** I believe this is artificially low because I've been using sodium bromide algecide. The algae shows up as greyish patches on the blue pebble tec. When I brush, yellow clouds float up into the water. Right now, we're brushing 1-2 times / day and get at least some new stuff floating up each time. Back in the spring, I thought it might be pollen, but this late in the year, it can't be and I'm starting to see some on the walls in addition to the floor now. Right now I have my chlorinator set so it's putting in one "puck" / day. We've had the pool about a year and I've been in the habit of putting in about 3 oz of Polyquat algaecide each week just as part of the normal weekly maintenance. When the problem first appeared, my first try was to put in a heavier dose of this per label instructions. The problem didn't really get any better so when that bottle ran out, my next try was Banish from Bioguard and 4 lbs of shock. That seemed to slow the problem for a while, but then it came back so my next try was Yellow Treat (sodium bromide) with 1.5 lbs of shock. I've done three applications of that now (to use up the container I bought), and even a day after putting it in, the algae is still coming back. One store just shrugged their shoulders when I described the problem. The next one (the one that got the high CYA reading) suggested a partial water change to drop those levels down. I'm inclined to try that since it's about the only option I haven't tried. The water is heating up fast here in Houston and I'm afraid the problem will get much worse with the warmer water. Through all of this, the water is perfectly clear. I was feeling pretty cocky after the pool was put in last year because things seemed to be going so well.. now I'm feeling pretty clueless. Any ideas on what else I can try here? Quote Link to comment Share on other sites More sharing options...
chem geek Posted June 15, 2009 Report Share Posted June 15, 2009 If it's yellow/mustard algae (instead of pollen) it usually shows up on the shady side of the pool since the algae prefers indirect light. If it's really yellow/mustard algae, then this is more resistant to chlorine. Nevertheless, if you used PolyQuat algaecide that should have kept the algae at bay along with a low chlorine level unless the CYA level is very high. It might very well be very high. You can dilute the pool water sample in half with tap water and test with your kit again (I assume it's a good drop-based kit and that the CYA test is a turbidity test, right?). If you are using test strips, then who knows what the true levels are. It is true that if the CYA is very high, it will be much harder to kill and prevent algae so a partial drain/refill is in order to lower it. Read Defeating Algae and other parts of the Pool School. Get your CYA lower before shocking with chlorine as it will take a sustained high FC level to kill this algae for good. However, be very careful and lower the pH first before shocking with a lot of chlorine since the rising pH from shocking can stain the pool since you've used Banish which has copper ions in it (at least doing a partial drain/refill will lower that copper level). By the way, what was the "shock" that was used? If it was Dichlor, then you've increased your CYA level even more. If it was Cal-Hypo, then that increases Calcium Hardness (CH) which probably isn't a problem in your vinyl pool unless your fill water is hard. Quote Link to comment Share on other sites More sharing options...
CurtisT Posted June 16, 2009 Author Report Share Posted June 16, 2009 ... (I assume it's a good drop-based kit and that the CYA test is a turbidity test, right?). ... By the way, what was the "shock" that was used? If it was Dichlor, then you've increased your CYA level even more. If it was Cal-Hypo, then that increases Calcium Hardness (CH) which probably isn't a problem in your vinyl pool unless your fill water is hard. Thanks for the response. Yes.. the test kit is a Taylor test kit where you put drops in until you can't see a black dot at the bottom of the dial any more. 100 is the highest reading in the kit and I was over that. I took samples to two pool stores yesterday to confirm my results... one got 150PPM, the other got 72.. go figure. The manager of one of the stores has graciously volunteered to come out to my house and take a look in person (that's a good way to earn my business even though they are someone more expensive than the other stores!). We'll see what he says... a partial water change seems to be the only thing I have left to try if he doesn't come up with anything new. The shock I've been using is just generic Cal-Hypo granules. Quote Link to comment Share on other sites More sharing options...
coppersnowblue Posted June 17, 2009 Report Share Posted June 17, 2009 It looks to me your cya is way too high. Your phosphate level is probably high too if you get rid of the phosphate algae is said not to be able to grow. Quote Link to comment Share on other sites More sharing options...
CurtisT Posted June 18, 2009 Author Report Share Posted June 18, 2009 It looks to me your cya is way too high. Your phosphate level is probably high too if you get rid of the phosphate algae is said not to be able to grow. Not sure if it's all of the sodium bromide or cya at this point, but either way, I think I'm going to have to drain some water to solve this problem. Can I just turn off the valves to the skimmers so the pump is only pulling from the main drain and open the plug on the bottom of my filter and let the water run down the drain (our MUD district requires drainage to the street rather than the sewer)? Quote Link to comment Share on other sites More sharing options...
CurtisT Posted July 2, 2009 Author Report Share Posted July 2, 2009 Just thought I'd post a follow-up. Because I was really getting concerned about what the sodium bromide (Yellow Treat) and high CYA were doing to me, I went ahead and did a 75% water change (overkill perhaps, but I decided I wanted to know what was in my water and keep it clean from there on). Spent about a week getting all of my parameters back in range and then hit the thing with 8 lbs of Cal-Hypo and a bottle of Copper Algecide to kill off the algae. That was 2 weeks ago and so far, no sign of any algae returning. The only issue I've got right now is keeping Chlorine in the pool with something like 9 days of 100 degree weather (even with CYA back up to about 60) so I've added some Polyquat to hopefully back me up on a day when all of the chlorine burns off. Now I head out on vacation for a week. I'll turn my auto-feeder back on (been feeding it bleach every day) and have someone drop a floating feeder into the pool about 4 days into the trip (I'll burn through the 7 tabs the chlorinator holds in about 4-5 days). Got my fingers crossed that I'll come back to no new problems! Quote Link to comment Share on other sites More sharing options...
chem geek Posted July 3, 2009 Report Share Posted July 3, 2009 Sounds like a good plan. Just be careful after having used copper algaecide that you don't get staining, especially if the pH gets too high. Quote Link to comment Share on other sites More sharing options...
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