Tweaking either pump run time or SWG % to get to optimum FC level

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QingGuy

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Mar 22, 2015
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Las Vegas NV
Here are my numbers:
FC - 3.5
CC - 0
pH - 7.8
TA - 100
CH - 250
CYA - 70
Salt - 3,450

I'm running my SWG for CH now, no pucks or adding bleach, for the past week each morning when I test (after 30 minutes of pump running) my FC is between 3 and 3.5 or minimum based on the Chlorine/CYA Chart with my target being 5. I run my pump/SWG for 9 hours each day with the swg set at 75%.

What would you recommend as my tweak to get to 5 every morning? Increase pump run-time or up my SWG %?

I debated where to post this here or in SWG so mod if you think the other area is more appropriate please move.
 
I have the same question. My pool opened for the first time in May. In the beginning, I had 9 hours of pump run time at 60% on the SWG. I found that I was overshooting on FC after a bit and so I reduced the run time to 8 hours. As the summer got hotter, I increased pump run time back up to 9 hours and then when I was borderline on the FC I raised the SWG to 80%. Now as the days are getting shorter I've kept the SWG at 80% but dropped the run time back down to 8 hours.

My assumption is that for the SWG life, 8 hours @ 100% is the same as 10 hours @ 80% so it would seem that maximum efficiency would be to run it with the shorter pump time with max SWG output. As long as that amount of pump run time is sufficient to keep your pool skimmed.

That's newbie advice so take it with a grain of salt ;-)
 
That is pretty good newbie advice!

Either is fine and it makes no difference, the SWG will be working and generating the same amount of chlorine whether it runs 100% for 5 hours or 50% for 10 hours. So, it is cheaper to increase the percentage because you aren't running the pump longer. Of course, that intelliflo pump is cheap to operate at low speeds so it probably doesn't matter much. I make chlorine with my pump at 1100 rpm which only uses 150 watts.
 
QingGuy,

What is the size of your cell? 9 Hours at 75% should get you to well above 5 ppm. I run for 4 hours at 50% and have a FC level of over 5 ppm with about the same size pool. So unless you have a very small cell, something is not right.
 
The IC40 produces 1.4 lbs/24 hr or adding about 1.7 ppm per day with your schedule and settings. So your extinction rate is about 33% which seems a little high for a CYA of 70 ppm even if you don't cover the pool.

Have you tried an OCLT?

If you pass OCLT and want to increase FC, then I would increase the SWG % to 100% to get to 4.7 ppm which should be good enough.

BTW, the minimum FC level for an SWG is around 3.5 ppm for a CYA of 70 ppm so you are probably ok at that level as long as you don't let it dip any further.
 
I haven't tried the OCLT, I can. My pool is full Vegas sun all day 7:00 a.m. to sunset and I don't use a cover.

Would you recommend OCLT? Going to have four teenage boys in the pool for a couple hours this afternoon will that create any issues with doing OCLT tonight?
 
The only reason I am recommending OCLT is that the FC extinction seems a bit high and it would just eliminate that as a cause. An OCLT is done after sundown so after everyone is out of the pool and the sun is down, you would measure FC and then once again in the morning. Make sure to mix the water before measuring but without adding any chlorine.
 

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QingGuy said:
This mornings results
6:15 a.m.
FC - 3
CC - Trace

So a loss of .5 overnight. Any thoughts on even with running my SWG 9 hours a day my CC is so low?
Click to expand...

Just be happy it is. There's no reason to be concerned with CCs if they are low. That's a good thing. CCs levels can be affected by organic matter, bather load, sunlight, etc. as long as they are less than 0.5ppm, you're good.

Your bigger concern is your FC. You are right on the edge of the acceptable lower limit. You need to increase your FC some more.


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mas985 said:
The only reason I am recommending OCLT is that the FC extinction seems a bit high and it would just eliminate that as a cause. An OCLT is done after sundown so after everyone is out of the pool and the sun is down, you would measure FC and then once again in the morning. Make sure to mix the water before measuring but without adding any chlorine.
Click to expand...
So what are your thoughts based on my OCLT, seems odd that my FC numbers are not higher.

JoyfulNoise said:
Your bigger concern is your FC. You are right on the edge of the acceptable lower limit. You need to increase your FC some more.
Click to expand...
Right, so I guess I just need to decide whether to run my pump longer or increase my SWG output from the current 75% setting. Or, do I maintain current settings, bleach to FC 5 and see if it maintains 5?

Also wanted to mention I'm confident in my CYA reading.
 
For giggles I upped the CH to 5 (recommended level for my CYA) and I'm going to keep SWG and pump time as is and monitor for the next few days. I cannot imagine that my SWG @ 75% cannot maintain 5 ppm. I'll update with my experience.
 
ping said:
Make sure the cell is clean of scale as that can cut down on the production rate.
Click to expand...
Checked it prior to installing (less than 30 days ago, new pool) and everything looked good. Installed about 5 weeks after pool was filled, all plaster dust was gone. I do know it has a self clean cycle it does after 30 days, maybe that will bump up production, wish I could remember the day in installed it.

Also thought I'd add I LOVE pool math. Added the exact amount of bleach it recommended, tested 40 minutes later and dead on 5 ppm!
 

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