"Shock" with SWG?

[cptkirk]

Some background before I get to my question. My SWG is rated to generate 1.45 lbs/day, which for my pool would raise the FC by 8ppm if run 24 hours at 100%. My FC demand is quite low (about .6 ppm/day) even with a relatively low CYA (in 30 to 40 range), and in season I generally run my SWG at 20% for 9 hours daily (which generates .6 ppm to balance out the loss) which keeps my FC in the range of 3 to 4 ppm. My CC is almost never measurable, but every now and then (maybe once or twice a season) it will get just a little pink when I add the DPD reagent. When this happens, I had been adding a pound of dichlor as "shock" (something I bought before I knew better). This approach seems to work OK since I'm not adding dichlor very often, but I would prefer not to use it going forward (particularly since the dichlor I have also has a little copper in it, I suppose presumably to "fight algae").

My question is, it appears I could get the same FC rise from running my SWG at 100% for 12 hours as I get from a pound of dichlor (about 4 ppm). Would this work just as well, or do I really need the "all at once" boost of added chlorine to get the desired result?

 

[Oly]

I understand your enclosure protects your FC from the sun, but with your CYA at 30 or 40 ppm and utilizing a SWG I'm not sure why you are targeting a FC level of only 3 to 4. I would raise your FC target level and avoid dealing with algae, the dichlor and the copper algicide. FC/CYA Levels
Use liquid chlorine to raise your FC level then adjust your SWG to keep you in the proper target range for your CYA. For a non SWG pool at 30ppm CYA that is 4-6 ppm and at a CYA of 40 it is 5-7 ppm FC. You may want to do an Overnight Chlorine Loss Test and diagnose if you have a bigger issue brewing.

 

[Jimrahbe]

Kirk,

If you just kept your FC at 5 or above you'd never have to add "shock" to your pool..

I always keep my FC at my target or above.. I never try to keep my FC between my minimum and my target.

Thanks,

Jim R.

 

[mguzzy]

Jim! I am and always will be your friend.. so from one friend to anther throw (or give) away the copper stuff. It will only accumulate in your pool and eventually stain. As the others have said, use the high end as your target not the low end. you can even go higher as long as you stay below SLAM FC and stay on the FC/CYA Levels. If you need to add an immediate boost to your FC use liquid chlorine.

 

[ajw22]

My question is, it appears I could get the same FC rise from running my SWG at 100% for 12 hours as I get from a pound of dichlor (about 4 ppm). Would this work just as well, or do I really need the "all at once" boost of added chlorine to get the desired result?

That is correct. There is no problem boosting your SWG output to get some more FC. It is helpful if you don’t have liquid chlorine on hand.

I would rather boost the SWG for a day or two then add dichlor.

 

[cptkirk]

This is a great forum, it has made me a much more well informed pool owner and I appreciate everyone's advice. I'm not ignoring the chart or the wealth of information about CYA/FC ratios on the forum. My water has always been clear, and I've never had to SLAM the pool. I recently did an OCLT just out of curiosity (no measurable loss) and I've also tested my SWG to see if it generates chlorine at the stated rate (it does). I'm comfortable with my operating parameters for my specific pool and usage patterns.

That is correct. There is no problem boosting your SWG output to get some more FC. It is helpful if you don’t have liquid chlorine on hand.

I would rather boost the SWG for a day or two then add dichlor.

This is really what I am asking. If I find I'm getting a slight uptick in CC, can I use a temporary boost in the SWG settings to clear the issue (before it really becomes a problem) or does it really take supplemental chlorine to take care of it? In other words, if I raise the FC over the course of 12 hours to the same level as I could by adding a jug of bleach (which I do not keep on hand), does it matter?

 

[ajw22]

This is really what I am asking. If I find I'm getting a slight uptick in CC, can I use a temporary boost in the SWG settings to clear the issue (before it really becomes a problem) or does it really take supplemental chlorine to take care of it? In other words, if I raise the FC over the course of 12 hours to the same level as I could by adding a jug of bleach (which I do not keep on hand), does it matter?

Does not matter. Chlorine is chlorine.

It can take you 12 hours before you pickup that liquid chlorine and by then your SWG has it in the water.

You are way overthinking things.

There is nothing in pool water chemistry that is very time sensitive.

 

[cptkirk]

There is nothing in pool water chemistry that is very time sensitive.

Thanks, this was the gist of my question, whether the time frame of the increase had anything to do with the effectiveness.

 

[ajw22]

Use the tools you have.

 

[mguzzy]

Thanks, this was the gist of my question, whether the time frame of the increase had anything to do with the effectiveness.

Only in that if there is a active bloom insuing that the SWG output may not be able to keep up with the resulting FC loss since it produces at a slow constant rate. But it sounds like you keep close tabs on the state of your FC. So it doesn't sneak up on you. If I know I am going to experience a high FC demand like a heat wave or pool party I will turn the swg out up a few days ahead if time to load up on FC.

 

[ajw22]

Only in that if there is a active bloom insuing that the SWG output may not be able to keep up with the resulting FC loss since it produces at a slow constant rate.

Depends how oversized the cell is in relation to the pool volume. Some folks have cells 4X or more oversized. They can get a good amount of FC pretty quickly if necessary.

 

[mguzzy]

I agree.. but the OP is only over sized by 2x.. so trying to Shock/SLAM/Superchlorinate with his SWG is not going to have the same immediate effect as dumping in a gallon of chlorine. If a small swing in FC is desired yeah use the SWG. If you need more then use liquid and save the SWG for maintaining. That was one of the best SWG lessons I learned on the forum.

 

[cptkirk]

Bottom line seems to be that if all I've got going on is a little CC, turning up the SWG to 100% for say 12 hours or so is fine. If I don't see the kind of FC rise that I would expect from that, supplemental chlorine would be called for.

 

[mguzzy]

You got it!