Struggling with algae reccurences

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surfhawaii

surfhawaii

0
May 18, 2011
69
Kailua, Hawaii
Not sure what I'm not doing wrong. Had cloudy, algae caused problem months ago. Shocked it. Fixed problem and returned to crystal clear. But, even though I kept the chlorine level within 2-8 over next week and a half, algae came back. Repeated the process but problem returned within a week and a half even though I kept chlorine within recommended level, most times at the 8 or 9 level. Repeat again.

One problem I also have had recently is trying to keep CYA up but I'm not sure what impact this has. Some months ago, CYA level was at 0. So, added 7 lbs of CYA. CYA level stayed around 30-50 for awhile but after the latest algae attack now notice it's back to 0. Currently adding another 7 lbs. Have been running pump, vacuuming (Dolphin premier) and back-washing regularly. My questions:

1. is this algae recurrence unusual? and if so, any ideas what I'm not doing correctly or should also be doing?

2. does the low CYA have an impact on algae formation even though I keep the chlorine level within range?

3. I've been doing this for years and haven't had this many algae problems until recently. However, I've noticed that I need to keep the chlorine level at 8 or slightly higher or algae returns. Is it ok to keep it this high? How about even higher? Would keeping it at 10 be that much of a problem for swimmers? Could it be that more sun in Hawaii means I need to keep chlorine at higher levels?

Thanks, Ben.
 
Hi Ben. I'm afraid algae recurrence is not normal. You should never have algae in the water. I suspect you have an imbalance of FC versus CYA that is related to this problem (see Chlorine/CYA Chart link below). When CYA is too low (below 30) FC gets burned by the sun too quickly. If CYA is too high (over 90) it take much more FC during the day to keep-up. You can se the relationship in that chart link below. A higher FC is perfectly acceptable as noted on the chart as long as the FC matches its corresponding CYA level. The trick to all of this is that chart ..... and making sure you are testing correctly to get those results. May I ask what test kit you are using?
 
Thx for reply. I use Taylor K-2006 kit. Yea, I think I understand need for CYA as a 'sunblock' but what I'm saying is that I was checking FC every few days and it was always at least 5 but algae still returned. I don't check the CYA that often but my thought is that if I keep the FC level within recommendations, shouldn't that prevent the algae from coming back? I mean, couldn't you maintain the pool without CYA at all? I realize that means you are putting in lots more bleach, but isn't that the real goal, keep the FC within limits?
 
One thing for sure ..... with no CYA the intensity or effects of chlorine upon everything in the water magnifies. So you never want CYA to go to zero. Even indoor pools that get no direct sunlight have a minimal amount of CYA to protect the swimmer's skin and any materials that may otherwise be sensitive to the effects of chlorine. Basically yes, you do want to maintain your FC at the ideal target FC based on the CYA. But even in the best of FC/CYA scenarios, oddities can happen. For example water circulation. If a pool has some dead spots where the chlorine doesn't move too well, it's more susceptible to algae growth in that area. Pools that have a lot of splashout, rain (water exchange) or even a leak perhaps can also see CYA drops that throw that FC/CYA balance off. CYA gets too low, FC gets eliminated too quickly throughout the day, then algae begins to form.
 
Ok, makes sense, guess I'll have to test CYA as often as FC and maintain it. Thx.

Related question. I thought CYA level was something that was pretty stable and immune to wild swings in value. Is it unusual for it to go from 30-50 to 0 in a matter of a month or so?
 
You are correct. Normally CYA is fairly stable, and you would not expect to see drastic changes either way. For our newbies, we would attribute those major swings primarily to testing error, either in how they stare at the black dot for a CYA reading or not testing outside under proper/natural light. The most common reason for CYA dropping is pool leak and/or areas with heavy rain (water exchange). Of course the most common reason for CYA spikes are using pool store products (tabs/pucks, bags-o-shock, etc).
 
One other question...lol well, for now anyway...is it ok to use a FC level of 10 on a routine basis? As I mentioned in first post, it seems that my pool struggles to keep algae out and I've found that keeping FC 2 -8 as recommended here, doesn't seem to be enough.
 
I haven't seen the word SLAM here. Did you just "shock the pool clear" using one-time spoke in chlorine? Or dis you complete the full SLAM process and pass all 3 tests? Did you look behind your light, remove and clean your steps, things like that? Or, it looked clear so you thought it was all good?

Also, you keep saying 2-8 FC range. There is not one appropriate range. For your cya level, there is a target, a minimum, and a SLAM level. Each day your should start at the target, so you don't fall below the minimum
It depends on your cya. You can go up to 10, but will that work to clear algae? Depends on your cya level, and whether you do the SLAM correctly.
 
The only thing that would cause your CYA to drop to 0 is bacteria that consume the CYA. It occurs rarely but is possible under the certain circumstances with very low FC. Under normal circumstances CYA should slowly drop 2-5 ppm per month.

Right now, I would set your CYA at 30 PPM and SLAM - Shock Level And Maintain your pool to kill the algae.

Once the 3 SLAM criteria are met then I would raise CYA to 50 and chlorinate based on the Chlorine CYA Chart, keeping it at target at all times and never letting it drop below minimum. And, of course, plenty of :paddle:
 

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By auto fill, you mean something that automatically replaces water? If so, no, I don't, but I watch this pretty regularly.

I brush after every meal...oh, wait...sorry, he he. I rely on Dolphin cleaner to do this, it climbs the walls and seems to do really good job at cleaning almost everywhere.

- - - Updated - - -

I did the SLAM correctly I think. Getting behind light is not an easy task and I can't remove steps, they've been tiled. However, obviously I'm not doing something correct or I wouldn't have this problem.
 
After a while, you can only use so much bleach and products until the imbalances or algae catches-up with you. Misleading clear water and filtering alone is also never enough. You asked if maintaining an FC of 10 is normal? It might be done in some unusual cases where a pool's CYA was allowed to skyrocket, but it's not ideal. In addition, it starts to make pH reading inaccurate. At this point, I would suggest posting a full set of numbers. We'll take a look and let you know what we think. The numbers usually unsolved most mysteries. :)
 
Well, I might have found one of my problems. I was getting inconsistent test results for CYA which indicated 30-40 one day and zero within a couple weeks. Today I was going to test and realized I had run out of reagent. Bought some new. Tested it and now level is at 100. I was adding CYA based on old reagent I think. Not sure how old it was but had to be a few years. Ugh, now I've really screwed this up. Will test again and if necessary, drain some water out of pool. But word to the wise...better make sure reagent is not past shelf life.
 
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