Very low CL - zero cyanuric acid - a-pilot SWG - next step?

poolSWG

LifeTime Supporter
Aug 29, 2007
15
Southern NJ
New IGP (vinyl) 22.5K, 48sqft DE filter, autopilot SC60

I have been running the the SWG since Monday evening (500lbs of salt added Monday noon - all disolved) Dig220 indicates 3200
Filter pressure 12psi

Could not measure any appreciable Cl level all week running pump and SWG almost 24hr/day
Monday: Power Level 1 @ 50% Cl = 0
Tuesday: Power Level 2 @ 50% Cl = 0
Wed: Boost 24hr Cl = 0.3
Thurs: Power Level 2 @ 50%
Had about 0.3 Cl last night according to a pentair drop test kit the installer left (I will be ording the TFP kit tonight).
Then Put 2 jugs or 6% bleach = 348oz about 9PM

Using the bleachCalculator should have raised Cl to 7.2

Took a sample to the pool store this with the following results at 8AM:
TA = 110
pH = 7.6 (my drop test indicated 8.2)
CYN = 0
TH = 130
TC = 6.3
FC = 6.3

Just tested water again (9.5 hours later) with test kit - ALMOST ZERO CL :!:
I just broadcast 4lbs of cynaric acid (most sitting on bottom) - may need a couple more lbs
A couple of questions:

Would zero stabilizer cause such a rapid Cl burn off by the sun?
Would the loss of some FC overnight (expected 7.2, actual 6.3) indicate algae?
Is the next step to bleach it again once the CYN level is raised?

Any suggestions would be greatly appreciated
 

pooladdict

TFP Guide
In The Industry
May 14, 2007
819
New Brunswick Canada
Yes on the zero stablizer an sun bleaching it out that fast.

You should put CYA into the skimmer, not directly into the pool.

Check your manual, not sure, but am pretty sure you will have some readings on your swg that will show electrical current and this will show that SWG is indeed producing.

Others will chime in soon, with far more knowledge then me, so be patient.

Rik
 

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JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Zero CYA would allow the sun to wipe out all of your chlorine very very quickly.

Transporting the water to the pool store tends to lower the chlorine level, so I wouldn't assume right away that you have algae or anything like that. On the other hand having chlorine near zero for a while will tend to bring on the algae.

Broadcasting stabalizer around the pool isn't the best idea. It is somewhat acidic so it could potentially cause minor damage to the liner. It also disolves very slowly. Putting it somewhere with lots of water flow speeds up the rate at which it disolves. So most people add stabalizer either through the filter or in a sock in front of a return.

With a SWG you are going to want a higher CYA level that you will get from 4 lbs of stabalizer. AutoPilot recommends CYA of 60-80. I would add some more CYA, say another 4 lbs to start, to the skimmer and then retest your CYA level in a week and add more as needed at that time (probably yet another 4 lbs, but wait to see).
 

poolSWG

LifeTime Supporter
Aug 29, 2007
15
Southern NJ
Thanks for the skimmer/sock suggestion - I will do that in the future. I can now see that it dissolves quite slowly. Would just using the vaccuum to get it off the bottom be better then just letting it sit? I would expect that to cause my pressure to rise a little bit until it was dissolved.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Vacuuming it up would be fine. I doubt it will have much impact on your pressure, the particles are too large to block much of the filter surface.