Jun 21, 2009

I have a 24000 gallon salt water vinyl liner pool with a chlorine generator. I just added some baking soda to increase my alkalinity and I am asking myself why. My levels are as follows:

salt 3000 ppm
pH 7.7
alk 50 ppm
free chlorine 3.5 ppm
cya < 20 (I will be bringing that up shortly)

The thing is, my pH just doesn't change much. If anything it tends to the high side of the acceptable range. The bicarbonate is going to shift the equilibrium to a higher pH and I am not sure I want that. Isn't chlorine more effective at a lower pH, say 7.4 than it is at 7.8?


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
As soon as there is any CYA in the water the whole chlorine more effective at lower PH thing stops being true, or rather becomes such a small effect that you can completely ignore it. For various other reasons, it is best to let the PH settle around 7.7 or 7.8 and TA around 60.

You don't want TA to be too low or PH can fluctuate way too easily. 50 is right on the edge of acceptable, though I recommend 60.

And obviously you need to raise your CYA level, which will bring the PH back down.

Don't try to micro-manage the PH. It is going to change a bit every time you add any chemical. If you try to keep tight control over it you will just end up adding unnecessary chemicals or worse not adding something your need. Just let the PH wander between 7.5 and 7.8 and adjust it if it is going to go out of that range and you will be fine.