Does an IFCS affect pH? Aggressive mystery pH rise.

[bradgray]

Howdy all,

Once in awhile we end up with a pool that seems to fight us a bit and behave differently than expected. In some cases it's an evasive pH rise.

We are familiar with all the typical culprits, but when none are relevant or we've ruled them all out, we can't help but scratch our heads and go hunting for ghosts. One curiosity has been if an IFCS aeration is able to generate a pH rise. I'm unclear on the science in terms of whether it needs to be surface turbulence, but I'd be willing to accept any such disturbance may trigger breakdown of CO2 regardless of its depth.

Is this correct?

 

[ajw22]

Eventually any aeration in the IFCS needs to get to the surface.

 

[JoyfulNoise]

There really shouldn’t be any air in the IFCS and it shouldn’t cause much surface turbulence because the heads should be directing their water flow at the floor so as to push dirt and debris towards the floor drain.

Does turning over water contribute to pH rise … possibly a little more than a stagnant surface but not likely enough to be “aggressive”.

What’s the TA and temperature of the pool?

 

[bradgray]

There really shouldn’t be any air in the IFCS and it shouldn’t cause much surface turbulence because the heads should be directing their water flow at the floor so as to push dirt and debris towards the floor drain.

Does turning over water contribute to pH rise … possibly a little more than a stagnant surface but not likely enough to be “aggressive”.

What’s the TA and temperature of the pool?

In the case of the most recent example, TA is 60 and temp is 70. Salt cell is disconnected, pool is covered with no recent use and chlorine is stable so no LC has been added recently, no spillover, no jets, no features. Just covered water with an IFC and filter pump. Has an intellichem but we've left the acid drum empty and pulled the LV for the stennor off because it would just lock out unable to keep the pH down.

 

[JoyfulNoise]

If the pool is covered then there is no outgassing of carbon dioxide possible and so the pH can not rise from the equilibrium reaction of dissolved inorganic carbon. So your options are some kind of chemical addition that is causing the pH rise OR faulty testing.

I would test the pH of a deep water sample using both reagent testing AND a properly calibrated pH probe. Make sure the reagents are fresh and make of few calibration tests using bottled water and tap water to ensure that the reagents and pH meter are testing as-expected. Distilled water should have a pH below 7.0 and bottled mineral water typically has a pH above 8.5 to 9.0. Tap water from a sink should be in the mid to high 7’s typically. Make sure that, in all cases, the FC is below 10ppm.

 

[jonpcar]

I agree with @JoyfulNoise that aeration should not be the issue as he is correct in that a pool system with no leaks and an IFCS will NOT introduce air into the pool.

BUT, water turbulence COULD be an issue, especially for popups at the top level steps/beach entrances/possibly benches as well. Also, many IFCS floor popups shoot all the way up the walls and clearly have turbulence near those surface areas (but not as much as the top steps, in my experience). I don't know how much this turbulence impacts pH.

In my IFCS system, I DO need to add acid constantly…about 4oz a day (of 32%) through swimming season. This seems to definitely be on the high end of acid requirements for systems. On the other hand, I believe that my pool’s pH rises even when I limit my IFCS use, but haven’t characterized this to know for sure. Eventually I am planning to add a pH monitor and compensate real time…that of course won’t solve the issue but it would allow this theory (of pH rise due to IFCS) to be verified, or not.

 

[JamesW]

In some cases, plaster dissolves and causes the pH, TA and CH to rise.

If the pH rise is due to plaster dissolving, then the TA and CH will rise by the same amount.

Are the TA and CH rising at the same rate?

What is the pH being kept at?

At what pH is acid added?

What are all of the readings?

What is the CSI range?

 

[bradgray]

If the pool is covered then there is no outgassing of carbon dioxide possible and so the pH can not rise from the equilibrium reaction of dissolved inorganic carbon.

This was also suspected. Thank you for confirming. I was unsure if the gaps at the edges and near the bond beam would suffice as escape routes for the outgassing.

So your options are some kind of chemical addition that is causing the pH rise OR faulty testing.

I would test the pH of a deep water sample using both reagent testing AND a properly calibrated pH probe.

Make sure the reagents are fresh

We've used two separate Taylor kits and the phenol red is brand new. Chlorine is 3ppm as of last test. It has been higher but not recently.

Tap water from a sink should be in the mid to high 7’s typically.

Spigot tested at 8 when we started the pool a year ago. But this pool is not losing water so we did not presume it was being diluted with high pH source water.

 

[bradgray]

In some cases, plaster dissolves and causes the pH, TA and CH to rise.

Pool is over 1 year and is pebbletech. I wouldn't expect such an issue with high calcium and high ph. Thoughts?

If the pH rise is due to plaster dissolving, then the TA and CH will rise by the same amount.

Alk is slowly trending downward due to the acid use. We're going to have to use bicarb in the next few weeks at the current demand.

Are the TA and CH rising at the same rate?

Hardness was between 200-300ppm last test on 1/4/24. We don't test hardness as often as other variables. I'm willing to confess this is not an element we focus on unless the pool water is aged or we begin to see scale.

 

[bradgray]

BUT, water turbulence COULD be an issue, especially for popups at the top level steps/beach entrances/possibly benches as well. Also, many IFCS floor popups shoot all the way up the walls and clearly have turbulence near those surface areas (but not as much as the top steps, in my experience). I don't know how much this turbulence impacts pH.

1/3 of this pool is stairs, with heavy density of pop ups on every stair. I'm feeling like we have something here.

 

[JoyfulNoise]

Does the auto cover float on the surface of the water or is it suspended?

 

[wireform]

Auto covers by design sit on the water except one foot from the walls where they are on an angle towards the water. To the point that if you lose a bit too much water due to evaporation or a small leak where the cover in the deep end has to pull too much over the back wall into the cover box, the amp limiter will kick out on you and shut the motor down.

 

[JoyfulNoise]

Well, if the IFCS heads on the steps create a lot of water turbulence and the cover is not in intimate contact there, then I suppose there could be significant aeration. One way to test that would be to stop using the auto cover for a bit and float a bubble cover on the surface that is cut to fit edge to edge. Then see if the pH rise is mitigated at all.

 

[JamesW]

Track CH and TA to see if they gain the same amount over time.

If the CH is rising with no calcium being added, then it might be coming from the plaster.

What is the CSI?

 

[mgtfp]

Can't you just turn off the IFCS for a while and see if the pH rise stops? Not permanently of course, just to confirm / rule out the IFCS.