What contributes more to pH rise?

[eqbob]

In general....which contributes more to the constantly rising pH in a SWCG pool?

The by-product of SWCG production (sodium hydroxide) or aeration?

Just curious.....

 

[jblizzle]

The by-product of the SWG ... is ... aeration.

 

[eqbob]

Hmmm... Ok. I don't understand that unless your talking about the hydrogen gas that also is produced?

I was talking about the aeration through water returns above the water lines..sconces, waterfalls, etc...

 

[JamesW]

An swg is mostly pH neutral when accounting for chlorine loss. Aeration is virtually all of the cause of pH rise.

 

[chem geek]

As described in this post, the production of chlorine in a saltwater chlorine generator or the addition of a hypochorite source of chlorine raises the pH, but the consumption/usage of chlorine is acidic where the net result in both cases is pH neutral. The exception is the small amount of excess lye in hypochlorite sources of chlorine and any undissolved chlorine gas from the SWCG that outgases.

Most pH rise in SWCG pools is from carbon dioxide outgassing which is higher when there is more aeration. The hydrogen gas bubbles in the SWCG aerate the water and as I mentioned there can also be some undissolved chlorine gas outgassing. The latter can occur more if you have a short pipe run from the SWCG to the return in the pool. If that is your situation, you can try pointing the return more downwards (or diagonally down for a round pool). As for minimizing the carbon dioxide outgassing, lowering the Total Alkalinity (TA) level and having a higher pH target will reduce the rate of pH rise. As shown in this chart pools are over-carbonated compared to the equilibrium amount of carbon dioxide from exposure to air. Finally, after lowering the TA level, using 50 ppm Borates provides additional pH buffering without being a source of rising pH itself.

 

[eqbob]

What is define as a short pipe run? Mine is well over 40' so I wouldn't think that would be short...
Is the equation set at the top of page 4 in this link
http://www.lowrycg.com/wp-content/uploads/2013/05/Using-Air-and-Acid-to-Get-Perfect-pH-and-Alk.pdf
correct?
If so, what creates the bicarbonate?