FCL - Not Enough

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
Recently had pool guy install a Hayward Aquarite 940. About 3 weeks ago.

My pool is approximately 20k gallons.

Things seemed to be going great. We run our pump 24 hrs, and with the SWG set at 50p the FCL built to close to 5ppm. We started turning it down to 40p, then 35p, then 30p. We stabilized to around 1.7 ppm. Probably a little low, but that’s where it was.

About a week later, the FCL is at 0.5ppm I figure, I got too aggressive with going low, so I put it back to 50p. The FCL never budged. 0.5ppm for a week. CCL stayed between 0.0 - 0.2. I contacted the pool guy, he said to put in Super Chlorinate. After 24hrs, we were up to 0.9ppm. Power cycled to clear the memory, ran Super Chlorinate again for 24hrs. FCL up to 1.8ppm. Repeat. FCL up to 3.0ppm. He wanted me to get to 3.0ppm. Seemed reasonable.

Turned it back down. Sunny day. A good amount of swimmers. Didn’t check it before bed. Pump ran all night. This morning FCL is 0.5ppm. I ask pool guy and he thinks it could be a high chlorine demand. Sunny day. Heavy use. Turn on super chlorinate, put a cup in front of a jet, test that water. I test it and it’s at 2.0ppm the water in the deep is 0.5ppm. (I can’t crack a union and test there because I have a broken arm - so the 2.0ppm isn’t crazy accurate, but it’s higher than existing so the salt cell is working somewhat). Seems like it should be much higher.

I’m just not sure what to think. It seems like my salt system isn’t generating enough chlorine. To keep it at 3.0ppm, I’d have to run it at 100p constantly. My pool guy, is a great guy. Very practical and seems honest. I believe we have a 3 year warranty on the unit, but he obviously wants to check everything first before we go that route.

Mind you, my water is crystal clear. Doesn’t smell. Feels nice. All in all, you’d think I’d be happy. PH may be a tiny bit high, but that’s to be expected with running in super chlorinate for a few days. Maybe I’m just testing it and worrying about it too much. I just don’t want to wake up to an algae bloom at some point.

Also, I should add that I have never shocked the pool since we opened it back in April. The CC has never been above 0.3. We just bought the house, the pool was green and black. I read on the forums and the site how to maintain a pool and it has been great so far. We wanted to switch to SWG for the water feel and no CYA issues.

I appreciate any thoughts, suggestions and comments.

My tests this morning:
AquaRite 940
Vinyl pool
Approx 20,000 gallons

Using LaMotte ColorQ 7
FCL 0.5
CCL 0.1
PH 7.7
ALK 78
CH 150
CYA 70
SALT 3200 (on panel of AquaRite and verified myself with a salt test)
Phosphate 700 (from pool store, I just had them test because I was in the area And wanted a double check)
Total Dissolved Solids 3700
 
Last edited:

Msch99

Gold Supporter
Bronze Supporter
Jun 11, 2018
908
Verona, MO
I would perform an OCLT. May have a bloom starting. Or turn off swg and chlorinated manually to see if is algae or swg not working. Betting on bloom.
 

crabboy

LifeTime Supporter
Jul 24, 2007
647
Suwanee, GA
One evening, add some bleach to get the FC up to between 3-5 and then run an Overnight Chlorine Loss Test (OCLT). This will let you know if there are organics consuming your chlorine.

Just a tip, to test the water straight from the jet, I have a short length of rubber tube that I'll stuff into the return socket about a foot, then I can fill from the other end of the tube. Its rare that I ever test that water, but it happens. I usually use that tube to fill the basketball/volleyball bases.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
Thank you for the fast responses.

So, even though I’m not seeing algae, I could have it and my Chlorine demand is just really high because of it and the SWCG is not keeping up with it. I just figured since all looked nice good, I didn’t have a problem with algae. Plus, since CC was always less than 0.5, I assumed I was good.

On the OCLT, if I get it up to 3-5 with bleach, I’m assuming I should shut off the SWCG? EDIT: Just read SLAM again which states yes to this question.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,824
Laughlin, NV
FYI -- Be sure the model of ColorQ you have can read FC in the 20+ ppm. You will be testing at that level for the SLAM.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
FYI -- Be sure the model of ColorQ you have can read FC in the 20+ ppm. You will be testing at that level for the SLAM.
I don’t believe that it can. I think it stops around 15ppm and only says HI. If so, I dilute the sample using distilled water and calculate. I did that in the spring when I had to use 80 gallons of 10% to bring the pool that hadn’t been opened in four years back to life. Haha.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
Then you need a FAS-DPD test kit for cases where your FC is above 10 ppm.
Thanks. I’ll get one. I’m also curious to try a different test kit because the LaMotte seems to be a bit sketchy with Alkalinity and CH. The exact same test water can show wild swings in those two if I test multiple times.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,824
Laughlin, NV
Good idea. The drop based kits are accurate. The ColorQ is not all the time. OK if you want to use it for spot checks, but the drop/titration kits should be used to base chemical additions on.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
Good idea. The drop based kits are accurate. The ColorQ is not all the time. OK if you want to use it for spot checks, but the drop/titration kits should be used to base chemical additions on.
Makes sense. I’ll follow the advice and report back in a few days.

I figured since CC was always low that I never really had an issue.
 
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Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
It will be a few days for sure. My wife and kids are going out of town later this week, and being that this is Pittsburgh - we don’t get that many sunny days. Since it will be nice this week, I don’t want to risk them not being able to swim. I’ll have to risk an algae bloom - but I’ll add some liquid to at least get up to 5.

If I do test at the salt cell or can get a rubber hose for testing at the jet, what would you expect the FC ppm to be? Getting ahead of myself a bit, but I do want to confirm the salt cell is doing what it should. Knowing that I do need to do all the other things above as well.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
Ok thanks. I will try an OCLT overnight and report back. I added in liquid 10% earlier because I had no FCL as stated at the beginning. Was probably around 8-10ppm most of the day. I will get it to 10ppm tonight and do the OCLT.

I don’t have a proper FAS-DPD test kit, since I just ordered it. I’ll use my ColorQ, recognizing that there may be an accuracy issue.
 

Patrickoleary

Well-known member
Apr 7, 2019
160
Greensburg,PA
I did the OCLT with my ColorQ. I didn’t have enough liquid to get to 10ppm. My results are posted below anyways.

FCL night 6.16 845 PM
FCL morning 5.16 630 AM
CCL morning 0.31

I’m away for the rest of the day so I out the SWG on just to keep some chlorine going in. Any thoughts?