Another SWG PH question

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stevodevo

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LifeTime Supporter
Dec 22, 2011
57
Gold Coast, Australia
Hi all,

Just wondering what the consensus is on SWG runtimes and reducing PH rise. I've read enough on this forum to know that the operation of a SWG inevitably means PH rise and reducing runtime (and elevated CYA) is the goal. My question... is it the chlorine output setting or the actual runtime that contributes most the the PH rise. In simple terms, supposing I can keep my water adequately filtered and chlorinated in 8 hours/day on output setting 50%, would I be better off running my chlorine output on 50% for 8 hours or 16 hours on 25% to keep the PH in check? For the sake of this argument, I'm not caring about electricity costs.

BTW - the examples above are hypothetical to keep it simple. In my smallish pool I've managed to get everything working good in the cooler weather running the pump for 6 hours a day on the SWG's lowest setting which is approx. 10% chlorine output. Every now and then I bump it up to level 2 if the FC has dropped a bit. In hotter weather I need to run it higher, but I assume my PB over-specced my SWG to allow for this (thanks Phil)... all good considering he was still the best package out of all the quotes I got.

Thanks,
Steve.
 
No difference. The % setting is the amount of time the cell is generating over a certain 10-15 minute period. So as stated above the cell would actually be on for 4 hours in both scenarios.
 
IMHO the pH rise when using a SWCG is related to the chlorine loss and also how much hydrogen is lost. The two factors are somewhat independent and at least partially out of casual control. Both are related to actaul loss of matter/mass of the pool that is replaced by the adition of hydrochloric acid.
 
It depends if there is any source of aeration other than the SWG. Say you have a spillover spa. The longer you run the pump, the more spillover there is, which is aeration, which raises the PH.

In the example stevodevo gave, the SWG is energized for the same amount of time either way (50% of 8 hours is 4 hours actually turned on, 25% of 16 hours is 4 hours actually turned on) so there is the same amount of PH increase from the SWG. But the amount of PH increase from other factors, i.e. any water features, can make a difference because of the different pump run times.
 
Thanks all. I've never noticed the cell turning off and on, but then again I probably have never stood and watched it that closely for a straight 10-15 min period. Having said that, my cell definitely looks like its generating a lot more at higher settings and less when set lower (going by how white the water looks as it passes through the clear chamber), so I always assumed it just runs at a certain power output for the entire runtime.

Seems the simple answer is it doesn't matter which way you slice or dice it, so you may as well save power and just go with the shortest run time.
 
Basically what Jason said. The water passing through the SWG causes aeration which raises the PH. Does matter if the SWG is on or off it still is aerating the water which in turn raises PH. Running a waterfall or fountain will do the same. So it's not the fact the pool is salt water it has PH problems. More that it is constantly being aerated which is reason. Lowering the PH a little lower than normal and I've that lowering the TA also has helped.
 

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