How much salt does liquid bleach add?

[chem geek]

First of all, why is your calcium rising? You don't seem to be adding anything that would increase calcium (such cal hypo for chlorine -- you are using bleach).

As for the other parameters, I can reproduce what is going on in your pool by assuming the following (converted to the equivalent as if it were done every day):
ACID: You add 8 ounces of muriatic acid per day PLUS there is an additional equivalent of 10.5 ounces of muriatic acid that is probably coming from the rain.
BUFFER: You add 14.6 ounces (weight) of sodium bicarbonate every day. This is equivalent to the amount needed to raise alkalinity by 20 ppm over 3 days.
OUTGAS: You are outgassing about 5.5 moles (about 8.9%) of your total carbonate in your pool).
CHLORINE: You are adding enough chlorine equivalent of 2 ppm per day. I also assume that this same amount is used up through normal processes each day.

It makes sense that your alkalinity drops faster with rain since the raindrops probably churn up the water and increase the rate of outgassing and you have a lot of that due to the wind anyway. When you say that during rains the acidity rises faster, did you mean the pH rises faster (which is actually more basic, not acidic)? If so, then that doesn't make as much sense since there appears to be more acid getting added to your pool from some source beyond what you add because your pH is not rising as much as it should just from the outgassing (alkalinity change).

If you are getting lots or rain, then I would expect all of your parameters, including calcium and alkalinity, to drop from dilution. Again, the rising calcium is a strange thing.

Anyway, there doesn't seem anything terribly wrong with your situation. When you have a pool exposed to the environment, you're going to be at the mercy of that environment. Only a pool cover that would keep the rain out would help.

That's my two cents.

Richard

[chem geek]

P.S. to last post.

Your increase in calcium may be due to the water you are refilling since it does have some hardness to it, but I didn't run through the calcs to see if that explains it all. When water evaporates, it just concentrates what's in the pool so if you add pure water you get back to where you started, but when tap water has something in it, then it gets added to what's already in the pool. It's possible the rain may add some hardness -- you could test your rain water to find out and also test it for salt which, as you surmise, may be where the salt is coming from (normally rain doesn't have salt, but maybe the winds mix up sea spray with rain during storms -- who knows, just test it to find out).

At any rate, a pool cover would also cut your evaporation and generally stabilize your pool. Other than that, I don't have anything to suggest except enjoy the pool!

[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