[Shock For Salt Water Systems]

Okay -- I understand. So I should bring my CYA levels up to normal first, and if I'm still not seeing adequate chlorine, I can take it from there. Right now, the generator has been running at 100% with the filter on for about 4.5 hours, and the chlorine levels are still barely being picked up by my liquid test kit. I did a test right at the return and I do get a higher reading there, so I know chlorine is being produced, just not holding.

[Shock For Salt Water Systems]

<!--quoteo(post=80149:date=May 24 2009, 07:54 PM:name=jkusmier)--><div class='quotetop'>QUOTE (jkusmier @ May 24 2009, 07:54 PM) <a href="index.php?act=findpost&pid=80149"><{POST_SNAPBACK}></a></div><div class='quotemain'><!--quotec-->Is one even technically "shocking" their pool when boosting SWG output for an extended period of time? I thought shocking implied breakthrough chlorination, i.e. increasing the FC level so quickly that CC is burned out - and I've read the slow FC rise via boosting SWG output won't accomplish that. Or is that BS? Just curious.<!--QuoteEnd--></div><!--QuoteEEnd-->

It's just BS. Yes, the superchlorinate will raise the chlorine slowly, but it will keep raising it, assuming the SWG is powerful enough. If the CYA level is high, you can get the FC level pretty high, but will be shortening the life of the SWG for no good reason. Shocking with separately added chlorine is the way to go, but is normally not necessary if one keeps the FC at a minimum of at least 4.5% of the CYA level (for SWG pools).

As for getting rid of CC, normal chlorine levels are usually sufficient. All that higher FC levels do is oxidize CC faster. There is no magic number where it "breaks through". The breakpoint chlorination curves usually shown start out with ammonia in the water and then chlorine is added so initially there is no measurable FC and instead CC builds up and then the CC drops and the FC can grow again. In a pool, that's not what happens since there is plenty of excess FC and the CC is continually being oxidized. "Breakpoint" refers to not having enough FC and then you reach a threshold where monochloramine can get oxidized; in a pool with some FC in it, the CC is continually getting oxidized.

Now if the CYA is high and the FC low, then the oxidation reaction can be slow taking hours for monochloramine and for urea taking many days unless the water is exposed to sunlight or the temperature of the water is high (as with spas).

Richard

I just converted to a salt system myself. I just want to make sure I understand correctly -- you're saying that we should really try not to ever use the superchlor function on the salt cell?? And that if we need to shock, we should only use liquid chlorine?? I'm stunned -- the main reason, after all my research, that I decided to switch to salt was that I would never have to handle noxious chlorine ever again! The only reason I was considering adding powdered shock (Leslie's PowerPowder Pro) was because the CYA is low (since the pool was just filled). I was then planning on giving away all my chlorine products!