Full sun, clear cover, CYA 55... And FC zero by end of day after SLAM

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T

themitzelfamily

0
May 18, 2015
30
Ann Arbor, MI
Okay experienced TFP pool operators... My DH and I need some help.

We live in SE Michigan and have a full sun all day pool. We have a clear bubble cover that is on whenever we are not swimming, though there is a lot of swimming and frequent "high bather load" situations. Our current CYA is 55 (I plan to take a reading tomorrow again to confirm), and our FC will go to zero during the day from well above the target FC. Recently went from 11 ppm to 0 in a matter of 4 hours, not in a SLAM situation.

We are currently at the end of a SLAM after FC dropping to zero... Water is and has been crystal clear, no appreciable CCs, and tonight it should hopefully pass the OCLT. Not holding my breath, but it looks promising. I have scrubbed everything including the skimmer and light niche (and we left the light out so the niche is getting SLAMed too) and we've been vacuuming a lot. During the SLAM, given no CCs, we put on the opaque winter cover to be able to hold chlorine during the day, and it is working when it is on (but we do swim daily). But we clearly have an issue with something... Not enough CYA? Need opaque regular cover? Backup anti-algae treatment? We just don't know what to do next, but it feels like the land of the neverending SLAM here. My DH is seriously considering going to the pucks in a floater to help keep FC up during the day. I am not ready to give up on TFP but right now our weekly liquid chlorine costs are way crazier than dumping water from excessive CYA when we need to shock in the future. It feels a teeny bit hopeless at the moment.

Got any advice? Any gut feelings on what might be going on here? This is our second year of pool ownership and our first year with chlorine (after successful Baqua conversion).
 
The advice is quite simple. Chlorine is consumed by two things......sunlight and organics in your pool. The CYA you have has minimized your FC lost to the sun so what's left? Organics (algae)

Going back to pucks will not do a thing for you except make your life more difficult. Giving up on TFP has nothing to do with us but it means giving up on understanding how to manage your pool and, reading between the lines, heading back to the Pool Store for the magic bullets they promise.

I am sorry to be so blunt and direct but algae can only grow in an environment that has inadequate chlorine and that is what has happened to you. There is no hidden answer.

The answers to managing your pool are all right here on this forum and there are thousands of people willing to help you but you must help yourself first by having a basic grasp of the process involved.

Chlorine kills algae. the least expensive and "best for your pool" type of chlorine is liquid. If you do not keep enough of it in your pool, you will grow algae again
 
It is important to maintain chlorine at or slightly above target level at all times for your CYA and the Chlorine CYA Chart. If chlorine drops below minimum level the the pool will be unsanitary and algae will grow.

With chlorine loss like that the only possibility is organic matter consuming chlorine, most likely algae.
 
Thank you for the advice.

Duraleigh: Blunt and direct are fine. We are not ignorant by choice :) We are simply new to chlorine pools, and despite doing a LOT of reading in the forums and pool school, we have very little actual pool experience. Which is why we're asking those with experience. And the point of the forums is to ask questions that need answering, right? Sorry if we are exasperating.

Pooldv: Thank you for pointing that out. We clearly were not keeping it up high enough to combat the organics and loss to sun. We are continuing to SLAM (at night and when the pool is covered with an opaque tarp, since we simply cannot keep FC up during daylight).

Since our tests are not making sense (to us, at least), today we took our well (fill water) and pool water samples to two different pool stores to see how accurate our home tests were. We bought a TF-100 earlier this season and have been using it for all of our tests. Here are the results (showing results for pool water only), all from the same water sample jar and all done within 2 hours of each other:

FC
Store 1: 7.38
Store 2: 5.8
TF-100: 9.5

TC (CC)
Store 1: 10.62 (3.24)
Store 2: 8.4 (2.6)
Tf-100: 9.5 (consistent readings of less than 0.5 CC)

pH
Store 1: 8.4
Store 2: 8.4
TF-100: 7.8

CYA
Store 1: 57
Store 2: 62
TF-100: 55 (repeated test with sample several times in shade of full sun, at waist level, and results were consistent as well as consistent with previous testing at home)

TA
Store 1: 167
Store 2: 231
TF-100: 210

Saturation index (good range is -0.3 to 0.3, apparently... I don't know what this means but we do not have any scaling)
Store 1: 1.5
Store 2: 1.4
TF-100: N/A

Calcium hardness
Store 1: 350
Store 2: 377
TF-100: N/A

Total dissolved solids
Store 1: 1520
Store 2: 2400
TF-100: N/A

No phosphates found

Does that change anything? Should we combat any values that are off? We are using muriatic acid with aeration to bring down the pH (and the TA) at present. Planning to continue SLAM overnight and continue testing, though now I really do not feel confident in our test results though they have been consistent, if different from what the pool stores said. We are doing everything possible to do them accurately, take samples from 1' down in deep end, keep pump running, etc.
 
Pool store tests are a waste of your time and are adding to your confusion. You need to go TFPC all the way.

It is important to maintain PH between 7.2 and 7.8. When it gets to 7.8 add acid to lower it to 7.2 and repeat. As you know, this will lower your TA gradually until TA and PH reach equilibrium. More here, Pool School - Lower Total Alkalinity

Chlorine level is set based on CYA level and the Chlorine CYA Chart. Always keep FC at or above target. Dose FC so that the next time you plan to test and add it will still be at target. It is safe to swim with FC between minimum and shock level. More FC is better than less.

Right now, you need to follow the Pool School - SLAM - Shock Level And Maintain process to get rid of the algae for good. It is fine to hold the FC just below shock level and swim. Be sure to brush, clean behind the light, under the ladder, pool cleaner and anywhere else algae might hide. Brush daily. Raise FC to shock level as often as you can. We swam ec0very day for a week and a half during our SLAM a month ago.

TDS and phosphates are not important in TFPC. Your CH is fine.

Read this, Pool School - ABCs of Pool Water Chemistry

CSI is ok from -0.6 to 0.6. See Pool School - PoolMath to calculate and tweak your CSI if needed.

Come back with more questions after you get all that memorized! :-D
 
The pool store tests waste your time. They are simply not as accurate as your own testing. Don't look upon them as reassurance but rather a source of confusion.

So, did you pass the OCLT? Could you post your numbers up please?
 
Thanks, all! No, sadly we did not pass the SLAM, about the same loss of 3 ppm overnight the night before last. Then loss of 7 ppm last night (21 down to 14). We have it under an opaque cover so we haven't been getting up at the crack of dawn to check (tell me if that is super bad practice). My DH does not want to add more during the day since it gets eaten when we swim anyway, so I imagine we'll be adding 26 ppm tonight. We have people coming over to swim today and tomorrow, but I might just keep the pool covered Tues and Weds and maintain above shock those days and see where we get.

We did the Baqua conversion at the start of the season... May. It took two weeks to pass the OCLT, but that made sense with all the goo we were cleaning out of there. It had been just fine until now, when we did an OCLT after the hose was left on to top up the pool overnight (2 weeks ago ish), and it failed. In retrospect, not sure if it would have failed the test before then and we just didn't know, but it *seemed* fine for about 6 weeks in there.
 

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one thing nobody has mentioned is this. there is no reason why you can't add some chlorine during the day. while the pool is in use. set up a quick lunch or snack, as soon as everyone gets out, do a quick FC test and dose as needed to reach target. While you're eating or whatever, the pump will circulate the chlorine and within 15-20 mins the pool is all set for more action. It is safe to swim as long as the FC is under SLAM level and since you're having trouble anyway, it isn't going to hurt the process.

Think of it like this: I have a SWG that makes chlorine whenever the pump is running. We use the pool regardless of running pump or not.
 
just noticed something that may help, you say CYA 55... There is no 55 on the CYA tube, so you are at 60 CYA, so you should be dosing above 7fc and never letting it get below 5..

After your SLAM I would shoot for FC 10 every night to make sure you are not below 7 the next night :) if you know there are going to be a lot of swimmers that day you can take it to 12 that morning and you should be "about" 7/8fc that night :)

after the SLAM you can test 2 to 3 times a day for a week or 2 to see where or if you need to adjust this strategy

so for your SLAM you should stay above a FC of 24 at all times

hope this helps :)
 
Lots of good info in there... Thank you all who have responded. Here is an intruiging update... Help me out with this...

This morning we tested the water at 8 AM (under the opaque cover). It was 14 (down from 21 the night before). I tested again at 12 noon and the FC was STILL at 14 (still under the opaque cover). We opened the pool to swim at about 1:30 PM. I just tested it again after 1 hour open to the sun (with several swimmers in the pool), and my FC is zero. I did the daily FC test and confirmed zero with the drop test. So... What is going on?

- - - Updated - - -

Let me address some point above:

We are leaving the opaque cover as much as possible during SLAM since no CCs are being registered, so no need for pool to "breathe", we're told.

If we add chlorine to the pool in the sun, like during swim time, it goes away immediately, as shown above... We didn't realize it was THAT fast, but it's fast. So.... Yeah. A waste of chlorine.

- - - Updated - - -

If our CYA is at 50-60 and we lost zero ppm to organics in 4 hours of darkness, isn't this an issue of inadequate CYA for our sun situation? No one has suggested we try a higher level, but that is what my gut is telling me. The pool looks perfectly clear and we are vacuuming/scrubbing like maniacs. What is the downside to trying? Dumping water when we need to SLAM?
 
When is the last time you tested CYA? Might need to test again to be sure bacteria didn't consume it. It happens inexplicably sometimes. Otherwise, the only explanation is organic consumption. Only two things consume chlorine, sun and organic materials. How old are the kids, anyone peeing in the pool? That will use up chlorine in a hurry.

As for not testing at the crack of dawn. I applaud you. :) I wouldn't and don't either. Sunrises are overrated!
 
Okay... New test to see what will happen. I covered the pool with the opaque cover (winter tarp cover). Then I upped our FC from zero to 7 ppm (confirmed with drop test after circulating for 20 minutes, 7 is target for 60 ppm CYA). I took out a clean quart glass mason jar of pool water and set it in the sun, on a white surface to approximate the pool. I will test both the pool and the sample after an hour and see if there are differences. If the sun is eating FC due to inadequate CYA, we would expect the sun sample to be much lower FC than the pool. If there is stuff growing in the pool and low CYA is not the problem, we would expect the pool to be lower. If they are both significantly lower I don't know who wins this round :) I will report back...
 
My test results are in. I used the basic Cl test, and the results are telling. The pool sample was above the max of 5 ppm, and the sample left in the sun was at 0. I will do a drop test tonight to see where we're at, and assess if we need to keep up the SLAM. Please reassure me that this means we need to up our CYA... or tell me what I am missing here.
 

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