Low FC - Any idea why?

Sep 3, 2007
21
#1
From a sample taken in the morning a few hours after the salt generator was shut off. The system was run for 12 consecutive hours overnight.

FC - 0.6
CC - 0.4
PH - 7.6
TA - 110
CH - 800
CYA - 40-50

I have the generation level set to max (100). I will be checking the chlorine levels again later today to compare.

I have a small amount of visible algae on the walls at the waterline. Aside from that, the pool is clear. I have been adding about 1/2 gallon of 10% liquid chlorine twice a week to supplement the salt system. If I don't do this, the pool will begin to green in about 2-3 weeks.

The salt system is an AquaRite and is about 3 years old. The salt cell was replaced last year. It initially made a higher level of chlorine (maybe a month?) but seems to have dropped down to the same levels above. I've been battling this problem from day one it seems, and have all but lost faith in SWG in general. The pool builder hasn't been much help beyond replacing the cell. They have their own store and seem to be more focused on selling me some snake oil to fix my problem (surprise!!). I get a different answer from every employee I talk to. The same holds true for other pool stores.

Is it possible that even with CC of 0.4 I have a chlorine demand high enough to keep the salt system from really doing a good job? Maybe my CYA level isn't high enough? Also, I have a waterfall feature, which I run constantly when the filter/SWG is on. Could this be contributing?

Any help is appreciated!
 

tagprod

LifeTime Supporter
Jul 3, 2007
489
Tomball, Texas
#2
I think all the chlorine that's being generated is fighting the alagae. Your CYA should be higher with a SWG - like 60-80. Get your Chlorine level up to shock level - 15 PPM maybe even 20 to be on the safe side and test throughtout the day making sure to hold it that high. It's good to test after sunset and test again in the AM to see how much the drop is. When you're holding chlorine overnight with no loss you've beat the algae. Good old 6% unscented bleach in the right amount will get your chlorine levels high enough.
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
#3
Schwim, the SWCGs are great at keeping a constant level of cl in the water! However, sometimes they get overloaded and algae can form, once it is visible, the SWCGs have a lot of trouble generating enough to fix the problem :( If your pool is at that point, you need to use unscented bleach to shock the pool and maintain that level until the algae is all gone (as per Brians instructions)

I suspect that at some point, either the salt got too low, the flow was restricted (causing the cell to shut off) or the chlorine demand was just too high (too many kids peeing in the pool, too much debris blowing in...) The other thing is that your CH is WAY TOO HIGH!! - break the cell down and see if it doesn't have scale on the blades!! Please check your diagnostic button -
The results (by # of push):
#1 water temp
#2 volts to unit
#3 amps
#4 % desired output
#5 instant salinity (with a "-" in front)
#6 model
#7 software revision

Please post the first 5 push results and I may be able to offer more help.
 
Sep 3, 2007
21
#4
I'll post those numbers shortly. Last I checked, they were all in spec per the owner's manual. This was about 3 weeks ago.

No scaling, I've been diligent to keep the cell clean. It looks clear right now.

Regarding the high CH, I'm told that the public water source here is like that, not much can be done. I guess I could test some tap water and see if replacing some of the water will help. Is there anything else that can be done about that? Could that be affecting the SWG output?
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
#5
Schwim, I was only asking for the #s to be sure that there wasn't scaling (the volts and amps will change if there is). If the 800 is from the fill water, there are ways to keep it from precipitating out into the water, and on to the cell, but I'll leave that for later.

I think that the pool got 'overloaded' for the SWCG and the algae took hold (if you are using the 'superchlorinate' switch for caring for this, please realize that it only works for the first 24 hrs. or until the unit shuts off, after that it goes back to it's regular % output)
 
Sep 3, 2007
21
#6
Got it.

Here are the numbers:

#1 water temp - 90F
#2 volts to unit - 23.0
#3 amps - 6.1
#4 % desired output - 100
#5 instant salinity - 3500
#6 model - AL-2 (is this right?)
#7 software revision - 1.32

Also, I just check the chlorine again - 0 FC, 0.2 CC. This was after a day of sun, no use. The pump was circulating water for about an hour prior to this test.

Forgot to mention - this is a 22000 gal pebble finish pool, in case that matters.
 

lsbarkley

LifeTime Supporter
May 15, 2007
98
New Jersey
#7
The Pool Calc says you need 730oz of bleach to raise up to shock level of 16 for your pool. Walmart sells UltraBleach for around $2.30 for 175 oz I believe. That is a little over 4 Jugs. I would buy more because the algae is going to use up a lot of that quickly. Maybe buy 8 or so if you can. Pour the bleach in the pool over a return to mix. Follow tagprods post about checking FC levels and make sure to brush the algae off the walls and floor. There are some stickies that will be helpful to read also. I just battled a case of algae myself...my two cents...be patient and you will get under control. The people at this site are amazing.

Ls
 

duraleigh

Admin
Mod Squad
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In The Industry
Apr 1, 2007
31,338
Sebring, Florida
#8
To emphasize what barkley is saying, you have algae in your pool and your SWG is not able to clear it out, You need to supplement the Cl capability of the SWG with bleach until you get rid of the algae.
 
Sep 3, 2007
21
#9
Yes, that is what I was thinking. I am troubled by the low FC output, but I guess that could be a side effect. It seems that low FC output is always the case in my pool, so I haven't been sure which came first - the low FC which allowed the algae to grow, or the algae, which prevents the SWG from making enough FC.

I will shock the pool and post an update.
 

duraleigh

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Apr 1, 2007
31,338
Sebring, Florida
#10
Actually, the low FC came first. For whatever reason, the FC got low enough in your pool to allow algae to get a foothold. Once it does, the demand for chlorine increases by a bunch and a typical SWG cannot supply this big increase in demand.

Once you shock your pool with bleach and get rid of the algae, I think your SWG will be able to supply enough FC to keep your pool clear......about 3-6ppm in your case.