Another Algae Thread

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Ivesmi01

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Sep 19, 2017
20
Mansfield, TX
Is it "normal" to take 7 days to get chloring usage down and CC below .5? I have been at shock level (25-40 fc) for 168 hours now and just tested CC and it's back up to 5. I just took out the lights (spa and pool) about 52 hours ago (since it was so cold and I hesitated on getting in the pool). I did take the lid off of the auto-fill and there was some slight brown looking dust so I treated it with bleach several times over the last couple days. The water has been crystal clear the entire time so i'm confused.

FC has been above 20 for the entire time
CC fluxuates from 2.5-5
PH started at 7.2
TA 70
CH 290
CYA 55
OCLT 2

I never saw any algae on the walls but did see some brown dirt looking stuff inside thhe light niche. I have had a brown dust on the bottom and tanning ledge when brushing, which attributed to construction across the street but maybe it was the start of mustard algae? The only reason I realized I had any problem was that i could not get my FC up to where I targeted. I chorinate with a Stenner pump and 8.25% bleach from Kroger. I have been combining the stenner pump and manual bleach dosing while doing this SLAM.

So is 7 days, even coming from a clear pool, a normal length for a SLAM?

Thanks,

Mike
 
2ppm FC overnight is a concern. Does your spa water mix with your pool? Any other places for algae to hide in your pool water? I have heard stories of folks having algae in their auto fill pipes, can you cap the pipes temporarily and see if it lowers your FC usage.
 
Hi Mike! :wave: Well, 7 days is getting to the point where you should be really fine-tuning a minor loss if any by now. So this is where we step back and review some basics since many times we get so caught-up with the SLAM ourselves we miss something right in our face. So here are some thoughts I'd pass along for you to consider:
- If you have no doubt about your CYA test, then I'd round-up 55 to 60. That would make sure FC SLAM level 24. But definitely make sure that CYA good.
- CC can fluctuate, and that's okay. While everyone thinks zero is required, as long as it doesn't exceed .5 we still consider that about the same - very little present.
- Your water is clear, so now it's a matter of that OCLT. The OCLT can be tricky for the following reasons:
-- CYA/FC balance requires adjusting or one of them were off
-- Still some algae undiscovered in the pool or equipment
-- Testing error (either at the start or end of OCLT)
-- Poor water circulation before either stage of the OCLT (should not apply since a SLAM requires the pump on 24/7)
-- Grabbing water samples from different parts of the pool

Your pool is fairly new, but something must be consuming chlorine you can't see if all the testing is good. I'd look under your skimmer lids, anything else that may still be in the pool, and especially that waterfall. Waterfalls, ledges, spillways, etc tend to leave pockets for stagnant water to collect and grow algae. I'm guessing your filter pressure isn't rising too fast, but if you haven't checked it lately, perhaps open it up for a good cleaning as well. I realize some of the things I noted you may have done, but wanted to point them out just in case. Hang in there and let us know if you crack the code on that pool of yours.
 
Texas Splash, Thanks for all the great suggestions! The Pool Calculator says CF 18 for a CYA of 60 (or am I missing something?) but actually I ran up in the high 30's for the first several days and only let it drift down to 22-24 the last couple days. I will look closer at the weir doors shortly. I always get the water sample from the same spot to hopefully eliminate variances in samples. I believe I have been testing correctly and verified my #'s by taking a sample to the pool store a couple months ago. I did clean the filter cartridges 3 weeks ago and my pressures looks no different than when I first cleaned them. I think I am going to keep the weeping wall running 24/7 as well now just in case there is something in there growing.
Oly, The mention of capping my auto-fill got me thinking. It's tied into my sprinkler system so over Winter the water may sit in the pipes a long time. Another possible source I suppose.
 
Another possible source I suppose.
Click to expand...
Absolutely! To give you an idea how much impact algae can have, some people have been known to leave pool toys in the water during a SLAM, only to find out the toys were filled with algae. It's a sneaky bugger.

As for the CYA-FC relationship, not sure about that CF 18 you were referring to, but if you're sure your CYA is at 60, then always refer to the Chlorine/CYA Chart to compare (link below in my sig). You'll see the CYA of 60 = a Shock of "24", and it sounds as though you've been in that area to begin with. It's good to be accurate though since too much bleach becomes a waste to the sun, so we don't want you to waste $$ either. :) Good luck this evening on your investigative work around the pool. If your weather is anything like ours in S.A., it's been beautiful, so enjoy it while you can. :sun:
 

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