How much FC should a SWG produce?

lmnconn

Well-known member
May 3, 2014
53
Missouri
Just installed a circupool SJ55 and I don’t think it’s producing as much FC as it should. When I run the SWG for 12 hours on 75%, the highest my FC goes is 6. The same holds true if I turn it up to 100%. I called Circupool and they gave me the run around about phosphates. They also recommended to raise my salt level from 3400 to somewhere between 4000-4500. I am currently adding more salt (slowly). Today I am at 4000 and I tested the water from the jet (using my vacuum hose to fill my vial so it’s not diluted). I have the SWG at 100%, and the Chlorine level coming out is 6. If it only comes out at 6, how could my FC ever rise higher than that? I know target is 6 for my CYA level, but I’d feel safer if I could get my FC to 7.

FC 5
CC 0
Ph 7.6
Allk 70
CH. 120
CYA. 70

Pool is clear and passes OCLT, so everything is fine there. I’m just wondering how high of a level of chlorine other people’s SWGs produce? I was thinking mine would be more
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,484
Bedford, TX
I,

I am not sure that you can just grab some water from your return and turn that into an output FC number for the SWCG.

In "Theory" your SWCG will produce 37.6 oz. of chlorine gas over a 24 hours period, when running at 100% output. That should cause an increase of 12 ppm in a 24K pool.

If you are running your pump for 12 hours, that would be an increase of 6 ppm over a 24 hour period, but (always a but in there...). Most pools use 2 to 4 ppm of FC per day.

You need to run the SWCG for a few days and monitor the FC valve at the same time each day and determine if the FC level is trending up or down... I would not base anything from just one test.

Thanks,

Jim R.
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
3,959
CT
Use bleach to get to your initial FC target, then use the SWG to maintain FC.
 

bobandsherry

Bronze Supporter
Apr 20, 2016
392
Riverview, FL
If your pool is clear of algea, passes OCLT, then you can verify your swg production overnight

1. First test what FC is
2. Turn swg to 100%
3. Test FC in morning before sun comes up, same process as when you would do OCLT

You can then use that to see what difference is. If FC was raised by 3 in 8 hours then you would approximate that FC production is 9 for full 24 hours. I wouldn't run at anything lower than 100% you can't be assured how many hours of active production there was.

Just my suggestion.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
4,957
Damascus, MD
I don't think your testing methodology is valid at all for measuring SWCG output levels. You are simply measuring the water at that moment in time coming out of the returns. I agree with others. Measure the chlorine at night, turn on your SWCG to 100% and measure again in the morning. Calculate the # of hours between the two tests to figure out daily output. That will give you a rough idea of the output. Mine is a relatively low output SWCG and I am constantly turning it off or down. I have it at 53% at the moment 24x7. It is fairly well stabilized at keeping daily 8ppm chlorine maintenance. When it gets to 9+ I turn it off or down until it is around 7. If I let it go it has gotten up to 15. We are in the pool almost daily right now. I had 5 people in the pool yesterday for probably 5-6 hours (including kids) and chlorine dropped only to 5. Pool gets full sun most of the day. I didn't even bump the SWCG output for that. So a lot depends on your pool usage and general cleanliness level. I am really anal about getting leaves out and clean the skimmer baskets daily and 2-3 times a week I run the robot.
 

lmnconn

Well-known member
May 3, 2014
53
Missouri
I have bumped it up to 7 with chlorine. It stays there overnight, but drops in the sun. I've been running the SWG from 3PM to 3AM. I check my FC before the pump and SWG come on at 3PM, when the FC should be at it's lowest point. I will lose 2- 3 PPM on full sunny days. The SWG will bring me back up to only 6. No matter if I run it at 75% or 100% and regardless of if my FC is at 3 or 4, it only brings it up to 6.

- - - Updated - - -

I have done all of this. My FC is usually 6 in the morning. I test again before the SWG comes on at 3PM. It drops down to 3 or 4. The SWG comes on at 3PM and runs til 3AM. The next morning the most I have again is 6. As I stated in my original post, it passes the OCLT. I have run the SWG at 75% and I've run it at 100%. It seems to make no difference. That is why I'm trying to see how strong it is coming out of the SWG.
 

ping

TFP Expert
LifeTime Supporter
Jun 24, 2011
3,134
Long Beach, CA
When you pass the OCLT are you running the pump over night and turning the SWG off? If not, try that tonight and raise the FC to 10ppm to run the OCLT.

If you are passing the OCLT while the system is running, then run another OCLT tonight but let the SWG run at 100% all night long. If you test at 9:00 PM and 5:00 AM the FC should have raised by around 4ppm.

I really think it is putting out about the right amount of chlorine each day. With it set to 75% and 12 hours the SWG should produce 4.4ppm of FC. If it starts making chlorine starting at 3ppm and adds 4.4 ppm during the run the FC would measure 7.5 but you haven't taken any loss during rest of the day. That would only take 1.5 ppm of loss for the evening hours, which is a lot but it seems your pool is losing a lot of FC each day. I would bump the CYA up to 80, it will make a difference.
 
Last edited:

bobandsherry

Bronze Supporter
Apr 20, 2016
392
Riverview, FL
You are not making much of a difference in chlorine generation between 75% and 100%, it only makes .4ppm more chlorine for your pool at the 100% setting.
I think your math is off. From what was mentioned above, the SWG produces 12ppm/day at 100%. For 12 hours, 3pm to 3am, that would be 6ppm. 25% reduction would be 1.5, right?
 

lmnconn

Well-known member
May 3, 2014
53
Missouri
I do the OCLT with everything turned off. I have 0 to only .5 loss. I have my salt bumped up to 4000 now and did get a little higher FC level reading. I’m going to raise it up to about 4200 so it falls within range of what the tech at Circupool recommended. Hopefully I’ll find the sweet spot where it’s happy. It has been VERY hot and sunny here, so if I’m getting by in this weather, I should be OK. It’s 2:30 PM and the temp is already up to 97 today! Thanks for everyone’s thoughts and suggestions.
 

ping

TFP Expert
LifeTime Supporter
Jun 24, 2011
3,134
Long Beach, CA
I recommend to always run the pump overnight when doing an OCLT. There could be something in the plumbing causing the FC to deplete, something might be hiding in the filter. Without running the pump you haven't ruled out the entire pool system of having organics.
 

bobandsherry

Bronze Supporter
Apr 20, 2016
392
Riverview, FL
I recommend to always run the pump overnight when doing an OCLT. There could be something in the plumbing causing the FC to deplete, something might be hiding in the filter. Without running the pump you haven't ruled out the entire pool system of having organics.
Agree, I experienced that my descents or bubbler may have been the cause, would have gunked up while I was on extended vacation.