Rate of pH rise since the converting pool to SWCG

[jaymantx]

Hi guys,

It has been about two weeks since I dumped bunch of salt in the pool, and turned on the SWCG. I am still trying to figure out the SWCG running schedule to get a stable level of FC. It's harder than I thought especially during the seasonal change in Texas.

One thing I have noticed since the conversion is that pH level seems to rise a lot faster than prior to the conversion. I do understand the chemical formula where the Cl that gets used up needs to be replanished by MA, therefore the increase in MA demand. Prior to the conversion pH jumped 0.5 (pH from 7.5 to 8) in 7-8 days, but it seems as though pH rises 0.5 in 3 to 4 days now. My FC demand during hot sunny day is about 3-4 ppm. Given this condition, does the pH rise of 0.5 every 3-4 days seem reasonable? My pool was finished 2.5 months ago, so I believe plaster is still raising the pH. Will this stabilize once the plaster cures more? How frequently do you guys add MA?

For the reference here are other readings:
TA: 70
CH: 325
CYA: 60
FC: 7
Salt: 3100 ppm

Thanks in advance,
Jay

 

[needsajet]

Hello there

You've probably read the Wikipedia article about MA replenishing Cl, which sadly is entirely incorrect and misleading, including the formulas. There are several incorrect things in that article. But suffice to say your only loss of Cl- ions is splashout, overflow and backwash. MA does indeed add some Cl- ions, but it's small compared to the salt. Cl- ions are not depleted by an SWCG.

There is nothing about the SWCG chemistry that raises pH. What does raise pH is aeration, and that's slightly increased by the bubbles created by an SWCG. It will not increase total consumption of acid, but will increase the rate of the pH rise.

The chemistry is very well described here: Pool Water Chemistry and within that thread just search for "SWG" and you'll find all the references. Post no. 3 has the chemistry of SWGs, and then there are other references elsewhere in the thread.

I add about 3/4 c. once per week, but I allow my pool to ride along at pH 7.9. I only add acid when I see 8.0.

if you want to spread out the frequency of additions, you can try lowering your TA. Your TA will continually rise from topping up water, and some is probably coming from your newish plaster. That effect lasts quite a while, sometimes more than a year. You'll notice that people with fibreglass and vinyl pools add a lot less acid than us concrete heads.

Cheers!

 

[bobandsherry]

I have SWG and I see pH rise about .5 or so every 3-4 days, my TA is at 60. I add about a cup MA every Wednesday and Saturday. If i do nothing it will rise to 8.2 and level out, but I've seen 8.4 after coming back from vacation leave. My pool is now 2+ years old so it's not new plaster. I do have my descents running, but honestly didn't see much difference when they were off, so I now just leave them on for the sound.

 

[jaymantx]

Thank you for your insight! You are right, I read it from Wikipedia. LOL I wonder if the SWCG bubbles are causing the faster pH rise. Weather has been colder and breezier.. Perhaps the wind? I plan to invest on a pH sensor and the CO2 gas tank actuator in the future for pH balancing automation...

Hello there

You've probably read the Wikipedia article about MA replenishing Cl, which sadly is entirely incorrect and misleading, including the formulas. There are several incorrect things in that article. But suffice to say your only loss of Cl- ions is splashout, overflow and backwash. MA does indeed add some Cl- ions, but it's small compared to the salt. Cl- ions are not depleted by an SWCG.

There is nothing about the SWCG chemistry that raises pH. What does raise pH is aeration, and that's slightly increased by the bubbles created by an SWCG. It will not increase total consumption of acid, but will increase the rate of the pH rise.

The chemistry is very well described here: Pool Water Chemistry and within that thread just search for "SWG" and you'll find all the references. Post no. 3 has the chemistry of SWGs, and then there are other references elsewhere in the thread.

I add about 3/4 c. once per week, but I allow my pool to ride along at pH 7.9. I only add acid when I see 8.0.

if you want to spread out the frequency of additions, you can try lowering your TA. Your TA will continually rise from topping up water, and some is probably coming from your newish plaster. That effect lasts quite a while, sometimes more than a year. You'll notice that people with fibreglass and vinyl pools add a lot less acid than us concrete heads.

Cheers!

- - - Updated - - -

That's good to know. Thanks for the reference! Maybe this is the new norm that I need to get used to.

I have SWG and I see pH rise about .5 or so every 3-4 days, my TA is at 60. I add about a cup MA every Wednesday and Saturday. If i do nothing it will rise to 8.2 and level out, but I've seen 8.4 after coming back from vacation leave. My pool is now 2+ years old so it's not new plaster. I do have my descents running, but honestly didn't see much difference when they were off, so I now just leave them on for the sound.

 

[spoonman]

Stenner pump for acid is a great solution if the problem warrants it. My pool has an insatiable thirst for acid and the Stenner has worked wonders.