Opinion on what seems like an overnight FC loss

[jorivesud]

Got new liner and pool fill on June 5th.
Brought FC to 12ppm for 2 days(June 6th and 7th), passed OCLT.
Let drift the FC for a few days.
Added CYA to bring to about 40.

Here are the readings since then:

date	FC	pH	TA	CH	CYA	SALT	SWCG	TempH2O	addition/action
9 juin	10	8	175	500		2600	off	62	16oz MA
10 juin	8.5	7.6	150	500	35		off	63	16oz MA + 28 lbs salt
11 juin	6.5	7.5	140			3200	off	64	16oz MA
12 juin am	6	7.4					1	64	Turn on SWCG
12 juin pm	5	7.5	120				2	74	16oz MA
13 juin am	5	7.3	110		35		2	74
13 juin pm	5	7.4					2	80	added 16oz CYA
14 juin am	5	7.4					2	77
14 juin pm	5.5	7.5					2	80	Clean filter
15 juin am	6	7.6					1	77	16oz MA
15 juin pm	5.5	7.3					1	77
16 juin pm	5.5	7.4	100				1	75
17 juin pm	5.5	7.6	100				1	75	16oz MA
18 juin pm	5.5	7.4	90		40		1	75
19 juin pm	5	7.6					1	75	16oz MA
20 juin pm	5	7.3	80	500			1	75
21 juin pm	5	7.4					1	76

22 juin pm	2.5	7.5					2	76	16oz 10% bleach(brought FC to 5)
23 juin am	3	7.6	80		35	3000	4	76	brought SWCG to 4
23 juin pm	4	7.6					4	77	8oz MA
24 juin am	3	7.4					4	77	8oz 10% bleach
24 juin pm	5	7.5	70				4	77
25 juin am	3						4	77

(am = 6am, pm = 4:30pm)
pump is at full speed from 6am to 5pm, then slow speed 5pm to 6am.
SWCG is not generating chlorine at low speed (low flow LED on)
Actions are taken after the reading.

Now, here is my concern:
- I seem to start losing FC overnight (~2ppm), but maybe I need to test later (around 9:30 instead of 4:30).
- What's odd to me is that from june 12th to june 21th, with SWCG set to lowest setting, I would stay at 5/5.5 PPM. And on June 22nd, I dropped at 2.5
- Water is crystal clear and has been since a few days after the fill.

Should I be concerned about that?

 

[ping]

If I'm reading your chart correctly, you are at level 4 for the SWG output % and with 11 hours of pump time that turns on the SWG, I get that you are adding 2.38ppm of chlorine a day. You should bump up the CYA to 60 for now and see how that works out. I don't see anything wrong with the SWG with those settings.

 

[DaninFLA]

you need to do your OCLT after sunset and retest before sunrise. while you are doing the OCLT, your SWCG needs to be off. Also, raise your FC up before the OCLT to maybe 10-15 for the test.

also, you are running your pump a lot more than needed. I have a SWCG, with a pool in full sun in Florida and I run my pump a total of 5 hours. doesn't hurt anything, just trying to save you some $$

 

[cowboycasey]

+1, bring your CYA to 70 or 80 and you should be able to run your pump and SWG about 6 hours and be good

 

[jorivesud]

Will do another properly done OCLT.
Reason behind the fairly long high speed pump run time is because I have many trees, and skimmer will capture better at high speed compare to low speed.
My CYA was kept low, since I had my SWCG set to minimum(1) and FC would stay at 5. Because of that I didn't want to raise it more and end up with too much FC.
Now, that I set SWCG to 4, I could raise my CYA. But, will do my overnight test 1st in case SLAM is needed.
But, I'm very puzzled at the steady state of the pool, to the sudden use of FC.

 

[DaninFLA]

gotcha on the high speed setting to skim. I would personally just run it at that then for the amount of time needed to properly skim/clean your pool.

remember, the SWCG can be changed by setting and duration. I.e. if you run it at 10% for 24 hrs, you will get the same amount of chlorine running it for 20% for 12 hours, or 40% for 6 hours and so on. so you have the ability to change as well.

also, your SWCG should be running while your pump is on the low setting...

 

[jorivesud]

SWCG has its low flow LED on when pump is on low, and won't generate Chlorine because of that.

I just went out and decided to look at the filter, and it was very dirty with pollen and insects. So, I clean it very well and replaced my pressure gage that was not working. This will help me monitor the cleanliness of the filter. It had been clean 15 days ago, so was assuming it would be good (without a working gage I couldn't tell until opening it).

Maybe, my filter was consuming the FC from being too dirty. Could that be it?

 

[jorivesud]

If I'm reading your chart correctly, you are at level 4 for the SWG output % and with 11 hours of pump time that turns on the SWG, I get that you are adding 2.38ppm of chlorine a day.

Out of curiosity, how did you get to the 2.38ppm of chlorine a day?
Do you have a formula somewhere?

 

[ping]

Your SWG is capable of generating 0.98lbs of chlorine a day and converting those numbers by how many hours you run the pump and the SWG output % I calculated that you were potentially adding 2.87 ounces of chlorine gas to the pool a day. I then entered that number into effects of chemicals in PoolMath and it calculates out to be 2.38ppm of chlorine in your pool.

There are other formulas that can be used to calculate out but the main numbers that you need are the maximum production in 24 hours which is .98lbs or 15.68 ounces, the SWG on time, and the SWG output %.

- - - Updated - - -

Your SWG is capable of generating 0.98lbs of chlorine a day and converting those numbers by how many hours you run the pump and the SWG output % I calculated that you were potentially adding 2.87 ounces of chlorine gas to the pool a day. I then entered that number into effects of chemicals in PoolMath and it calculates out to be 2.38ppm of chlorine in your pool.

There are other formulas that can be used to calculate out but the main numbers that you need are the maximum production in 24 hours which is .98lbs or 15.68 ounces, the SWG on time, and the SWG output %.

 

[jorivesud]

So, I did OCLT, but forgot to raise FC.

June 25th, 9:15pm: FC: 5.2, CC: 0
June 26th, 5:50am: FC: 4.6, CC: 0

It seems like my dirty filter was likely eating my FC.

 

[DaninFLA]

So, I did OCLT, but forgot to raise FC.

June 25th, 9:15pm: FC: 5.2, CC: 0
June 26th, 5:50am: FC: 4.6, CC: 0

It seems like my dirty filter was likely eating my FC.

you need to redo it with a high FC, will magnify any decreases. you had 0.6ppm...wouldnt be surprised if that's over 1ppm when you raise it to 15ppm and redo. for example, you had a 0.6ppm loss from 5.2...that's a 11.5% decrease in FC. if you raise it to 15ppm, a 1ppm drop would be 6.6% decrease in FC. so you are double. But its not really a linear relationship...so retest with high FC and report back.

dirty filters aren't eating FC anymore than algae in your pool, its all in contact with the same water/FC

 

[pooldv]

Agreed, OCLT should be done with at least 10 ppm FC.

Usually when a filter gets that dirty that fast it is because of algae starting to grow in the pool.

Here are the early signs of algae growth:
1 higher than normal chlorine consumption, gets a little worse every day
2 filter getting dirtier much faster than normal
3 slightly slimy pool walls or small 1/4" patches of algae, gets worse every day
4 slightly cloudy water, gets a little worse every day
5 water starts to turn green
6 frogs and salamanders move in and it is officially a pond!

With an SWG this can be a fairly slow process over one to several weeks. You don't always get all symptoms but any one or two of them is your early sign to manage your pool a little more closely and probably keep a little more chlorine in the pool.

 

[jorivesud]

Ok, as per recommendation, I did an OCLT at higher FC.
- brought my FC to 15 at 9:15pm yesterday. (Might as well bring it to shock and be ready if SLAM was needed)
- brushed the pool thoroughly.
- this morning at 5:30am, it was at 14
- SWCG started at 6am, at 9am I was back at FC = 15
- I will leave it like this and do another OCLT tonight.

A drop of 1 is enough to think I could have something growing?

 

[jorivesud]

Last OCLT results:

Sunday night 9pm, FC: 14.5
Monday morning 6am, FC: 14.5

I guess I had something that was just about to start, and seems like it got tackled on time and could be killed quickly.
I will now let my FC drift to regular level.

Thanks for not letting me ignore it.

 

[Texas Splash]

It's a good feeling when you know you've done it. Enjoy.