Recurring "annoyance-level" algae... what am I doing wrong?

[Steverino]

Longtime TFP follower here... Pool particulars in the signature.
For the past couple (maybe three) seasons I've had minor-ish pesky green algae. Pool opens great in mid April - crystal clear. SWG is consistently doing its job - FC is currently around 7, so a bit high perhaps for a SWG pool. No combined chlorine. CYA is 85-90. Despite this, I started to see some algae on the walls/floor in mid-late May. I run my robot weekly, usually two cycles each time 'cause it isn't really good at getting everywhere. It also doesn't brush the edges & corners, so I follow up with a weekly brushing of the entire pool with a pole & Wall Whale brush.

By the end of a week, the green is creeping in again - not badly, but you can easily see a green haze in a few patches starting to form here and there. Water is still crystal clear.

Last two seasons when this has happened, if I do a SLAM (Walmart chlorine FTW), I can usually knock it out and the rest of the season is pretty much autopilot with no green stuff and minimal attention. My question is - WHY? Prior to these last couple of years, I have gone years with no need to SLAM.

I know I can go buy a shopping cart full of chlorine and SLAM yet again, but I'd like to know how this keeps happening. Grateful for ideas and welcome your questions.

Thanks!

 

[HermanTX]

It could be that you are on the edge of the range and there is just some minor algae lurking in the skimmer or behind a light.
CYA of 90 the target range is 6-12. It may drop enough one hot day for the algae to take hold.
When you open, do you start out using LC or go straight to SWCG? It might be best to raise FC to the high side of the range for the CYA and monitor it.
Maybe @newdude has further ideas.

 

[Steverino]

Thanks for the reply... Your points are good! Somehow in my mind I was thinking my FC was high-ish - shows I shouldn't trust my memory. Definitely could be some algae lurking - it is almost impossible to get the ladder steps totally brushed off. I've always opened just with the SWCG - I only break out the LC when desperate...LOL.

 

[Pool Amateur]

I also had that problem in the past, and the light niche can be a problem child. for me it was the solar cover which I believe the water on top of the cover gets the direct sunlight and lowers the chlorine level of that water as it is not remixed. I solved it by doing a couple of things:
1) Increased my target FC from 5 -7
2) stopped using solar cover (not because of algae)
3) closer monitoring and adjusting of SWG levels or leaving filter run longer. As summer gets hotter or real sunny days pool uses more chlorine than earlier in season or when cloudy. Rain can also dilute the chlorine concentration. If I am having a lot of people over especially small children, I turn pump on early, leave it run later than the timer setting or increase the output.
4) run the pump/SWG during the hottest part of the day when the chlorine is being burned off the most. Again all this at trying to maintain the 7 target. I also usually run the robot when done swimming for the day and then once in the middle of the night to keep circulation going while pump is off.
5) Use a SLIME bag near end of SLAM or when I loose that "Sparkle"
6) Introduction of algae from ladder or toys or other objects brought into pool

Other thoughts, do you SLAM pool when opening? CYA of 90 is a bit high and a pain to SLAM. It has been my experience if I do not keep my FC SLAM level 1-2 point above the target SLAM takes a long time to get real clarity or what I call the "Sparkle" of the water. I believe that could be due to several reasons:
1) error on my CYA reading or FC level. (probably much more CYA, I think FC is usually pretty accurate) If you are always at the low end of the target this could be the straw that breaks the camel's back.
2) when FC drops below SLAM target it really decreases effectiveness of killing algae.

Hope this helps

 

[Steverino]

Thanks for the reply! Yeah, my CYA is a tad higher than I'd like. It was too low at the start of this season, Pool Math told me how much to add - but I must have mis-read something and overshot a bit.
I also stopped using my solar cover years ago when the third one finally disintegrated. It was just a pain to use (freeform pool and no good, easy place to store the reel), and sometimes I felt like it actually encouraged algae growth. Pump is currently set to run for 10 hours at 2700 rpm. I've bumped up my SWCG to 100% for the moment (was set at 80%). I think I'm also going to order a new set of test chem - mine are probably borderline age-wise.

 

[drsipe]

Not that I want to contradict what pool math says, but with anything that builds in the pool and can only be resolved by drain/fill (CYA, salt, calcium hardness), I only add 1/3 of the recommended dose in pool math, wait till completely dissolved and mixed, and test again, and repeat the process until I am the range I want to be. It takes longer to achieve the correct levels, but I don't overshoot. For some reason, that I don't fully understand, it seems like CYA is one of the chemicals that is very easy to overshoot, so I'm very cautious.

Second thought, I prefer to be at the upper target range as opposed to the lower end of target range.

Maybe I'm a little too conservative with my pool, but, since adopting the TFP method, I have had a crystal clear pool, and have never needed a mid season SLAM.

 

[Steverino]

That's good advice... I would probably do better if I paid daily attention instead of weekly - allowing for finer tuning of things, and slower ramping up as you suggest.

 

[Pool Amateur]

Once set I only usually test 1-2 times per week, unless big party or something unusual, I know real hot sunny days take more also, so I just SWG up another 10% without testing and usually I am very close to 7. I think your big problem maybe not slamming at the beginning, you still have some residual algae that you are not seeing, then something happens that gives it a leg up and you see green. I have limped through the end of the season by bumping up to 8, but it is early enough to SLAM, just takes a lot of chlorine. In the beginning I use 12.5% 5 gallon jugs because it is most economical and fastest.

drsipe,
I do not think you are contradicting pool math, but it is easy to misread CYA, Salt is pretty accurate for me and I do not test calcium hardness and never had to adjust for it. But going up by a third or half is probably good advice so you do not overshoot. but for FC once you know your gallons it is spot on and I rather be a little over than under so I dose at the recommended amounts because I am lazy, if a little over it goes down fast. Again if I am shooting for 7 and hit 8, no big deal to me.

good discussion