SWG or Algae?

[tcat]

I've been struggling with FC drop. Slammed a few days ago at 20, passed all overnight tests. Had been keeping FC at 9 or 10 for a couple days with Edge-40 at at 3 LEDs. Gradually dropped to 6, so I bumped it to 4 LEDs. Noticed it dropped to 4.5 end of day yesterday, and 1.5 this AM. CYA 60-70. Had CC zero to .5 for past week! Going to crank the Edge up to 6 LEDs to see if it starts going back up today. Never had this issue with Liquid Chlorine.

 

[mknauss]

Link your Poolmath data or post up recent water chemistry data.

 

[tcat]

Cya = 60-70
FC = 3 (added last of my LC)
CC = 0-.5
TA = 110
CH = 400
Salt was 3500 a couple weeks ago, haven't checked, but no low salt indicator.

Bumped Edge up to 6 and changed 8hrs to 9 hrs. Will check FC end of day.

 

[mknauss]

How much FC are you generating each day?

 

[Jimrahbe]

T,

If you can pass the OCLT, then to check the SWCG's output you can run what I call the Overnight Chlorine Gain Test..

Run the same as an OCLT, but with the SWCG on full blast. Test your FC just after sunset, and then again before Sunrise, and the result should be an increase in your FC that matches whatever your cell is designed to generate, over the test period.

Thanks,

Jim R.

 

[tcat]

How much FC are you generating each day?

Good question. I had set at 8 hours, "full blast" should be 14oz., set at 3 LEDs should be about 4-5oz. FC should be going up 3-4 per day (and down). Will see what 6 LEDs does tonight. Water temp 84 degrees. Use to take about 40oz liquid per day to keep up.

 

[mknauss]

As you transition into summer the FC loss per day will increase. 3-4 ppm FC per day should be good right now if your CYA is 70 ppm. Be sure to test the CYA level every month.

 

[tcat]

Whenever the pump goes from 1750 to 2750 (or zero to prime), tons of bubbles come out of jets (one in particular), as if the whole line was full of air. Looking at my cell it looks full of gunk, but could just be bubbles. It's only been 3 or 4 weeks, so shouldn't need cleaning. Just seems like it's not producing. Will see tonight, plan on running on full. With less than .5 CC, don't think algae could be doing much.

 

[tcat]

At least it quit going down! Was FC 2.5 at 6, 3 at 7. If I calculated correctly, FC should go up about 1 every 2 hours (cell generating 1oz per hour). In theory should be FC 9 at 7 am. Thinking I just had cell set too low for the heat. CC was zero with FC at 3.

 

[Newdude]

So this is *exactly* what you are testing for this time of year. For the first half of the season, each UV increase will just randomly appear and you have to match it. It might be 2 weeks or 6 weeks. Test, notice, react.

The back half of the season you will overproduce when you miss an adjustment time. Whoopsie the FC is a 12!!!! BOY is the pool clear tho.

 

[laprjns]

Good question. I had set at 8 hours, "full blast" should be 14oz., set at 3 LEDs should be about 4-5oz.

So I think you are calculating the cell's production a little on the high side.
Your Edge is rated at 27.2 oz (1.7 lbs) of chlorine gas per day (24 hrs) or 1.1 oz per hour. Running it "full blast"for 8 hours results in a total of 9 oz of chlorine gas. In your pool (15,000) gallons that will add 4.5 ppm FC. Running the Edge at 37.5% (3 LEDs) for 8 hours will result in 3.5 oz of chlorine gas and add 1.7 FC.

 

[tcat]

Well, 12 hours at night, full 8 LEDs, only raised it 2ppm, went from 3 to 5. CC .5 at most.

 

[tcat]

7pm 3.0
7am 5.0
9am 6.0
7pm 6.0

24 hours at 100%. Bad cell? Hate to run 24/7 at 100%, but beats going to find chlorine!

 

[an1vrsy]

SWG are used to maintain a level of FC in your pool. I haven’t read through this thread, but once you get to you target, you can set the SWG to maintain that level. It might be 50% for 24 hrs. Or 100% for 12 hrs.

 

[tcat]

SWG are used to maintain a level of FC in your pool. I haven’t read through this thread, but once you get to you target, you can set the SWG to maintain that level. It might be 50% for 24 hrs. Or 100% for 12 hrs.

Yes 30 or 40% for 8 hrs should keep up, 24 hours at 100% barely does.

 

[Newdude]

24 hours at 100%. Bad cell? Hate to run 24/7 at 100%, but beats going to find chlorine!

I sure hope it's not bad. You should be producing about 13.8 FC a day.

How sure are you about the CYA ?

Many in the hot climates need to go to 80.

 

[tcat]

Yes, and all I need is 3 or 4 (42-48 oz 10% bleach always took care of it). Unless SWG degrades faster than liquid chlorine in heat, something is definitely wrong. I'll check CYA again, I can get 50-70 depending on the light, but even at 50 the cell should still produce plenty. Would CH of 400 degrade the cell in a month?

 

[Newdude]

I'll check CYA again, I can get 50-70 depending on the light

We all know it's questionable at best. But 50 probably wouldn't hold up too well to the 92 degrees tomorrow. The cell would still win, but not by much. You picked up 3 FC yesterday after losing about 3 (per normal with LC) so the cell made at least 6FC of the 13+ expected. Seeing how you passed the OCLT and that cells generally either work or die, it's more likely you lost 10 FC to the sun and ended up +3. Or, one of the polarities is defective and the cell is only producing half of the time it's on. 6 + 6 would be closer to the expected 13.

 

[tcat]

Except it was 100+ degrees today Going to run oclt again tonight.

 

[Newdude]

Going to run oclt again tonight.

Pass it so we feel better about possibly raising the CYA. You can never run too many OCLTs. They are free.