SWG and pH.

[rjb1211]

I figure I am going to be a pain on here for a while as I just got my new equipment installed which includes my first experience with SWG.

In the past I was constantly adding acid to counteract the pH rise from adding liquid chlorine. What should I expect from SWG? I couldn’t get Pool Math to tell me.

 

[ajw22]

Chances are you will see the same pH rise with a SWG as with liquid chlorine.

 

[Newdude]

Target a 60 TA and 7.8 PH. Only run any waterfeatures 15 mins a day to flush them when you aren't out there enjoying them.

I figure I am going to be a pain on here for a while as I just got my new equipment installed

I'd like to point out that the TFP army literally shows up all day. everyday, to help folks. Why can't you be one of those folks ?

We get low key sad in the off season when it's quiet.

 

[mas985]

Liquid chlorine will raise PH only temporarily. As the FC gets used up, the PH drops back to where it was before that CL was added. Pretty much the same thing for the SWG chemistry. It is only temporary and should not need a PH adjustment for those factors.

PH - Further Reading

www.troublefreepool.com

However, there could be other reasons the pool experiences PH rise such high TA/PH fill water.

 

[rjb1211]

I read the Further Reading section on this and it seems to make sense but that hasn’t been my experience over 25 years of adding liquid chlorine or bleach. I could count on pH going from say 7.6 to 8.0 after adding the necessary amount of bleach over a few days. At that point I would add enough acid to take it back down to 7.6. This is excluding any rain or other fill water.

With SWG I am anticipating a more consistent FC level and maybe that will help keep the pH from rising aa much.

 

[mas985]

Correlation does not imply causality.

The science is solid for the chemical reactions. Plus if you do the math, the amount of PH rise due to a typical dose of CL is actually quite small.

 

[Bperry]

I read the Further Reading section on this and it seems to make sense but that hasn’t been my experience over 25 years of adding liquid chlorine or bleach. I could count on pH going from say 7.6 to 8.0 after adding the necessary amount of bleach over a few days. At that point I would add enough acid to take it back down to 7.6. This is excluding any rain or other fill water.

With SWG I am anticipating a more consistent FC level and maybe that will help keep the pH from rising aa much.

If you were following typical advice to keep the TA between 80-120 then that would explain your fast pH rise. If you keep it lower at 50/60 the pH rise is very slow.

 

[rjb1211]

I was keeping TA around 80. Is that wrong?

 

[ajw22]

I was keeping TA around 80. Is that wrong?

TA down to 50-60 is ok.

Let your TA find an equilibrium with your pH.

Forcing TA and pH to numbers just causes it to seek out equilibrium.

PH TA Relationship - Further Reading

www.troublefreepool.com

TA - Further Reading

www.troublefreepool.com

 

[rjb1211]

Thanks. I just played around with numbers in Pool Math and keeping TA at 60 and pH at 8 gives a good CSI value.

 

[Bperry]

I was keeping TA around 80. Is that wrong?

The higher the TA gets, the faster the pH rises.

 

[ngc4900]

So a TA of 50/60 does not cause any damage to the pool equiptment etc.? My TA is at 110 and I am tired of having to throw in Acid every 3 to 4 days. Thanks

 

[Bperry]

So a TA of 50/60 does not cause any damage to the pool equiptment etc.? My TA is at 110 and I am tired of having to throw in Acid every 3 to 4 days. Thanks

Nope, perfectly fine. In fact the reason you have to add so much acid is because of your TA.

TA of 80-120 is good if you only use trichlor pucks for chlorine because those are acidic and lower the pH and TA slowly as they dissolve.

 

[ajw22]

So a TA of 50/60 does not cause any damage to the pool equiptment etc.?

Nope. Not as long as your pH stays stable and rising. pH behavior is an indicator if TA is getting too low.

My TA is at 110 and I am tired of having to throw in Acid every 3 to 4 days. Thanks

Throw in acid to keep your pH in the 7's.

High TA can cause scaling in the SWG. Read TA - Further Reading

 

[ngc4900]

I just re-read pool school about lowering TA with acid and then using aeration and repeating. I have a water fall feature built into my pool and I can turn my returns up to the surface. PM also states you can use the SWG to aerate the water. How does one do this? Thanks.

 

[ajw22]

. PM also states you can use the SWG to aerate the water. How does one do this?

Where is that said?

 

[Bperry]

I just re-read pool school about lowering TA with acid and then using aeration and repeating. I have a water fall feature built into my pool and I can turn my returns up to the surface.

Your TA will lower itself without any effort if you just manage the pH and not add any more baking soda. No reason to lower it any faster than natural unless your fill water TA is really high and pushing the TA up in your pool.

 

[proavia]

Please provide a specific reference where is says the SWG can be used to aerate the water.

A lower TA (in the 50-60-70 range) will help slow pH rise. Of course, it will take acid additions to lower the TA.

Keep your CSI in the 0.00 to -0.30 (negative 0.30) range to minimize scaling in the SWG.

 

[mas985]

I just re-read pool school about lowering TA with acid and then using aeration and repeating. I have a water fall feature built into my pool and I can turn my returns up to the surface. PM also states you can use the SWG to aerate the water. How does one do this? Thanks.

An SWG creates hydrogen gas bubbles, when it is actively generating chlorine, and gas bubbles increase the surface area of the air/water boundary so that carbon dioxide removal from the pool water is also slightly increased. But the volume of bubbles tend to be quite small so the effect is also small. An air compressor can also be used to create this same effect and is generally more effective than the SWG would be.

But by far the waterfall will likely be the most effective method. That will not only create air bubbles under the surface but also increase the surface area of the pool to air boundary by creating waves.

lastely, Simply running the pump will also increase the release of carbon dioxide by bringing more carbonated water to the pool surface where it can then be released. Pointing the returns to the surface also increases the release rate.

But as was stated earlier, the PH will rise on it's own without the addition of any "extra" aeration.

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

Aeration can be provided by a SWG, spa jets, waterfall, fountain, return pointed up so it breaks the surface, air compressor, kids splashing, rain, etc. this one, and this one show examples of home made fountains and this post shows a spa style jet that fits into a return.

 

[ngc4900]

Thanks everyone, Mark found it above. Per your recommendations, I will let the TA drift downward on its own.