Chorline drop with CYA...Can a SWG keep up?

Florida Penguin

Platinum Supporter
LifeTime Supporter
Mar 23, 2008
:?: 12,000 Gal pool
Jandy Aquapure 1400 SWG
Solar cover on, but waterfall on and spa spillover always on.
Heated to 88 degree F.
3 months old, just acid cleaned SWG last week (due to lack of Cl was keeping the cell in reverse mode trying to clean it....after acid wash, it was working goes in and out of reverse mode normally)
All tests below are with TF-100 kit

I noticed my FC levels were dropping often, even after the acid clean of the SWG. Checked CYA and it was 40. I confirmed water tests with local store (TF-100 matched up pretty close to the store testers).

I added 3 lbs of CYA 48 hrs ago. I also added 96 oz of bleach at the same time and a few hr later, the FC was about 7-8. This AM (which is aobut 36 hrs past adding both bleach and CYA), the FC was 2.5.
My SWG runs for 10 hrs a day and I have the SWG set for 80%.

So, after the above results, I ran the SWG for 12hrs at 100% to see what would happen.

This evening, (now 48 hrs since adding CYA), the CYA=80 on the TF-100 test kit (as predicted by chemgeek's spreadsheet ..thanks!). The FC is now about 3.

So I am a little concerned. I would have guessed that at 12hr of 100% output, the FC would be up more than just the 0.5 that I got today. This is not even summer yet, and I have the solar cover still on. I am not sure if 10 hrs of 80% output during the summer will hold the FC at the 4.0 that I need to keep it at.

My hopeful thought is that the CYA is still soaking up the FC and that most of the SWG output today went into the CYA buffer.

So I added some bleach tonight and I got the FC up to 5-6 range.

Does this sound resonable? Should I be worried? I think my SWG is working. The FC did go up, just not as much as I would have liked. Additionally, the pH is definately rising faster when I crank up he % output (pH was 7.5 two days ago, now it was I added some acid today as well.

Other labs....TA=90, ph 7.5-7.8 range, CA=350, salt 4000, no CC (all chlorine is FC), boric acid about 30-50 ppm, never had an alge bloom....and pool is crystal clear now.

Any thoughts? Thanks. :?


LifeTime Supporter
Jul 24, 2007
Suwanee, GA
I think you've got problems with your SWG. My PB started my SWG at 40% and the CL was over 15 when I first checked it and my pool is a bit bigger than yours at 21k. I'm currently at about 10% with water temps at about 60 and it is holding an FC of 2. With 80%, 88 degree water and a 10 hour pump time our CL should be sky high. I noticed that your salt is a bit higher than jandy recommends between 3.2 and 3.5.

Have you tried emailing Jandy support? They have been pretty responsive when I contacted them in the past.

Florida Penguin

Platinum Supporter
LifeTime Supporter
Mar 23, 2008
8) I called my builder. He thinks this is about par for this unit after adding CYA.

Here is South Florida, he said it is not uncommon for the SWG to be at 80% or more during the summer months. Also, he often suggests supplementing with bleach/chlorine right after big pool loads, esp. in the summer.

He thinks the SWG would be giving some kind of error code or it wouldn't work at all. It either works or doesn't work, there is no state where is works not as good (as long as the salt, etc. is OK).

He thinks the combination of the recent addition of CYA plus that I keep the pool 88 degrees is putting a high chlorine demand on the pool, even if the solar cover is on.

Any input on this is appreciated!


TFP Expert
LifeTime Supporter
Mar 29, 2007
Coastalish 'down easter'
If you want to check the cell - you can fill a bucket with pool water and disconnect the cell, place it in the bucket and trick the flow sensor into thinking the pool is running. You should see hydrogen gas accumulating and after a minute a cl test for the bucket water should be very!! high.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Something must be wrong somewhere, that doesn't sound normal. The 1400 is rated for pools up to 40,000 gallons, it shouldn't be anywhere near 80% in a 12,000 gallon pool. Common causes of low FC levels include: low CYA level, low salt level, scaling on the cell plates, short pump run times, algae, and malfunctioning SWG.

If I am following your report correctly you now have the CYA level at 80, which is fine. The pump is running 12 hours a day, which is fine. Salt level is 4000, which is fine. You just acid washed the cell and didn't see any scale on the plates. That leaves algae and a malfunction. Clear water does not rule out algae. I suggest you use bleach to bring the pool up to shock level (FC level above 20) and see if that clears things up.


LifeTime Supporter
Oct 5, 2007
Valrico, FL
Another possibility is that you have a low level infestation. Late last year I had to increase the output of may SWCG from 7% to over 30%. The water was clear, no unusual amount of CC, just a high chlorine demand. At first I thought it was the SWCG, I even had the Mfgr come out and check it. However later I shocked the pool, and now my setting is back to normal. So it is possible to have something growing in your pool and the only sign is an increase in chlorine demand! I suggest trying to shock your pool and then see if the chlorine demand returns to normal.

Florida Penguin

Platinum Supporter
LifeTime Supporter
Mar 23, 2008
:-D Thanks for all the advice...

I kinda did what most suggested. I addeded extra bleach the other night. (didn't test afterwards, so probably not enough bleach to get to the shock level (based on past experience.)

Anyway...this morning I was at FC of 3. I am now 4 days out from adding CYA. I ran the SWG at 100% for 12 hrs again today and tonight I have a FC of 7 (Yeah!!!)

So, I think my orginal thought of the CYA soaking up all the FC output may have some truth to it. My theory is that now the CYA is fully dissolved and saturated with FC, so the SWG output is now reflected in the rise of the FC level.

I will back down the SWG output to 60% and bring it down slowly over the next week or two while closely watching the FC levels.

I will try the full shock treatment next if needed.

As a side note....I do not know how people can keep a pool in top shape without a good test kit for FC, etc, etc,...
I talk to people all the time who do none of this testing and "seem" be doing OK with their pool...however, there always seems to be a catch. For example, they usually say, " Everything is going fine, and I just add a little of this aglacide stuff once a week and I have no problems..." My suspicion is that they are masking a bigger problem and after some time, they will run into trouble with their pools.

Thanks again for all your input....