How much salt does liquid bleach add?

[chem geek]

Another thought. Since you seem to be having a lot of outgassing of carbon dioxide, you might consider running your pool at higher pH and lower alkalinity, say start at 7.4 or 7.5 and lower alkalinity to 80. See if you still get the same amount of pH rise and alkalinity drop (after adding acid to restore the pH) as you do currently. If it's better, then this is an option for you.

The relationship between carbon dioxide outgassing is shown in the following link (CO2.png) where you can see that there is a rather large change in the relative rate of outgassing from a change in pH and a lesser dependence on alkalinity. The difference between pH 7.3 and Alk. 100 (relative outgas rate 20) and pH 7.5 and Alk. 80 (relative outgas rate 7) is almost a factor of 3 difference which may be enough for the 7.5 and 80 combination to be stable enough for you to live with. At least it's worth a try and with your current situation it should be easy enough to see how it goes. Of course, you may still bounce in pH from 7.5 up to 7.6 but you may not need to add as much acid as before.

If you try this, be sure to report back your results. I'm trying to see what sort of relative outgas rates are "tolerable" in different situations. Right now you'll see the "Limit" line in the graph at around 15, but this is somewhat arbitrary and dependent on the amount of aeration (and you have quite a lot due to the wind and rain).

Richard

[smallpooldad]

Wow,

I am so impressed with your knowledge and even more with your kind help.

I will try all you suggested and report back. For the next few days I am removing iron stains and will be draining the pool on Thursday or Friday.

One last thing I did a phosphate test before the iron treatment and it was beyond a 1000 ppb, most probably airborne pollution and leaves falling from a nearby tree which I net out daily. I wonder if this level could cause problems? I have no algae issues but I will now use a phosphate remover from SeaKlear to control this, do you have any opinions on this?

Aloha,


Paul

[smallpooldad]

Ok,

If we lower the Alk to 80 should we use a CYA adjustment for 50 at 7.5?

In other words should the indicated Alk on the test be higher?

Aloha

[chem geek]

Ok,

If we lower the Alk to 80 should we use a CYA adjustment for 50 at 7.5?

In other words should the indicated Alk on the test be higher?

Aloha

Good catch. I misread your earlier post where your real TA dropped from 120 to 100. Generally when we report TA on this forum we report the test measurement's Total Alkalinity that is not adjusted for CYA. If you adjust the TA for CYA, then this isn't TA anymore it's Carbonate Alkalinity instead (CA? -- could get confused with CYA or CH so we just don't use this). When we get all the numbers including TA and CYA, we can do the appropriate compensations as needed.

So yes, drop your actual measured TA from 120 to 100 and let the pH rise a little to 7.4 or 7.5 as a starting point. Then see how much acid you are adding to keep the pH stable. If it's less and if it seems like your fighting the rise in pH less, then this is a better alkalinity to be at. If there is little or no change, then you are experiencing something that we've seen on the rising ph levels thread and we don't yet have an explanation for it. So if the lowering of alkalinity doesn't help your pH rise and acid usage, don't sweat it. There isn't anything you are doing wrong.

Richard

[smallpooldad]

Thank you,

I will report back in a week.

Aloha

[smallpooldad]

Well thank you it worked brilliantly. The outgassing theory worked very well despite high winds blowing over the pool from the remains of a tropical depression.

At a pH of 7.5 and an adjusted Alk of 80 I have not used any acid or baking soda in a week.

So from now on, if you do not mind, I will address you as St. Outgasser, and your theory as the Gospel of Outgassing according to Chem Geek.

Aloha and thank you once again for all your kind help.

[chem geek]

I just got back from vacation and was pleased to see your post reporting the positive results of lowering TA and increasing pH to reduce your pH upward drift and your pool's demand for acid. Glad it worked out and that I could be of help.

As for the name, I'll just stick with chem geek for now. I won't even go where the "outgassing" jokes lead...

Richard