Swimming pool chemistry startup from well water - how slowly would you add ~3 cases of acid & ~50 pounds of calcium?

Gary Davis · Jul 30, 2024

Due to illness, the belated startup of my pool happened last week where for the saturation index (at the current 69 degrees Fahrenheit & 7.6 pH), I need roughly around 3 full HASA cases of 31.45% muriatic acid (to drop alkalinity from 270 ppm to 100 ppm) and just under about 50 pounds of calcium chloride (to raise calcium hardness from 290 ppm to 400 ppm), where my only question in this thread is how long would you take to add that amount of acid incrementally?

Given it takes about a month (or so) to fill the pool shell at about an average of a thousand gallons a day (which is all the well pump & booster pump can handle), there's no chance in using any of the filtering or self-cleaning circulation system, but I'm doing just fine using home-made self-engineered ad hoc buckets.

Using buckets for dissolving and for dilution while I'm slowly filling the pool, even without the pool equipment running, I'm easily slowly incrementally dosing to the requisite 7.5% of the CYA HASA chlorine sanitation (at ~3.25 ppm) & 30 ppm endgoal CYA protection (there is infinite sunlight and no cover) & 400 Calcium hardness endgoal needs by pouring a 25% dilution of chlorine and dissolving the almost-impossible-to-dissolve CYA granules and exothermic CaCl flakes into buckets - where my main question about timing is about the dozen gallons of HCl mostly.

How long would you take to slowly incrementally add a dozen gallons of hydrochloric acid to a pool by hand?
Would you take a month? A week? A few days?

DrewLG · Jul 30, 2024

Gary Davis said:
How long would you take to slowly incrementally add a dozen gallons of hydrochloric acid to a pool by hand?
Would you take a month? A week? A few days?

If I were unusually focused on keeping the chemistry balanced while filling a 35000-gallon pool over ~30 days, I would do this:

I'd test pH every day as I filled the pool, and I'd use PoolMath to determine how much acid to add to that day's actual volume to drop pH to 7. And then I'd add that.

I wouldn't care whether I used all of the 12 gallons before the pool was full.

Meanwhile, I would add half a pound of CYA the first day, and one pound of CYA every 3 days after that. And I would test FC every day and dose the pool with chlorine to 10ppm.

Gary Davis · Jul 30, 2024

DrewLG said:
If I were unusually focused on keeping the chemistry balanced while filling a 35000-gallon pool over ~30 days, I would do this:

I'd test pH every day as I filled the pool, and I'd use PoolMath to determine how much acid to add to that day's actual volume to drop pH to 7. And then I'd add that.

Thanks for the advice to balance daily what I've got in the pool, which, at the moment, is about half of the 38K gallons or so (I'm not quite sure how many gallons the pool holds but it's around that number).

At the current 70-degree (unheated) temperatures, I know for sure that the well-water buffering alkalinity has to eventually massively go down as the calcium hardness has to equally eventually massively go up if I want a balanced saturation index to remain in a +/- 0.3'ish range that allows the pH ceiling to not be so high as to push the sanitation efficacy into the pH +8 range.

DrewLG said:
I wouldn't care whether I used all of the 12 gallons before the pool was full.

That makes sense to treat the pool as if it was only the gallonage that's currently in it, and dose the acid daily accordingly even as the one chemical that is the most difficult to add sparingly is the muriatic acid when you know three cases will eventually be needed.

DrewLG said:
Meanwhile, I would add half a pound of CYA the first day, and one pound of CYA every 3 days after that.

Again, it's a good idea to bring up the CYA from zero to 30 ppm slowly, where, luckily, adding too much doesn't harm anything (except add to the CYA alkalinity a bit) as I know CYA will be diluted moving forward with the filling.

DrewLG said:
And I would test FC every day and dose the pool with chlorine to 10ppm.

This I'm already doing where, given there is no bathing load or particulate load, I'm keeping the FC at about 7.5% of CYA plus a couple of PPM (roughly about 2.25 ppm plus about 2 ppm) for about 4 to 5 ppm (where I've been adding the chlorine at dusk for the obvious lack-of-sunlight reasons).

I generally buy about 3 cases of acid and about 6 cases of chlorine at the local dealer, who is far away (I live in the boonies) so I only go to that part of town infrequently - and he gives me a good volume-discount price (yes, I know chlorine degrades over time).

DrewLG · Jul 30, 2024

Gary Davis said:
At the current 70-degree (unheated) temperatures, I know for sure that the well-water buffering alkalinity has to eventually massively go down as the calcium hardness has to equally eventually massively go up if I want a balanced saturation index to remain in a +/- 0.3'ish range that allows the pH ceiling to not be so high as to push the sanitation efficacy into the pH +8 range.

Ok, but two things:

1. Your CSI can be in your target range with much less aggressive management of TA and CH than you are proposing. For example, these levels will give you a CSI of 0.280:

FC: 5
pH: 7.6
TA: 200
CH: 290 (unchanged from your fill water)
CYA: 30
Temp: 70F

And then, after the pool is filled, if you want to adjust CH higher and TA lower, you can do so slowly and gradually as you periodically add acid to counter the natural pH rise.

2. You'd want to keep your pH below 8 for other reasons, but just for correctness: Remember that with CYA in the water, pH has much, MUCH less effect on sanitation efficacy than without CYA. You've probably seen these graphs before -- the red lines (HOCl) are the important ones:

Bperry · Jul 30, 2024

Gary Davis said:
Due to illness, the belated startup of my pool happened last week where for the saturation index (at the current 69 degrees Fahrenheit & 7.6 pH), I need roughly around 3 full HASA cases of 31.45% muriatic acid (to drop alkalinity from 270 ppm to 100 ppm) and just under about 50 pounds of calcium chloride (to raise calcium hardness from 290 ppm to 400 ppm), where my only question in this thread is how long would you take to add that amount of acid incrementally?

Given it takes about a month (or so) to fill the pool shell at about an average of a thousand gallons a day (which is all the well pump & booster pump can handle), there's no chance in using any of the filtering or self-cleaning circulation system, but I'm doing just fine using home-made self-engineered ad hoc buckets.

Using buckets for dissolving and for dilution while I'm slowly filling the pool, even without the pool equipment running, I'm easily slowly incrementally dosing to the requisite 7.5% of the CYA HASA chlorine sanitation (at ~3.25 ppm) & 30 ppm endgoal CYA protection (there is infinite sunlight and no cover) & 400 Calcium hardness endgoal needs by pouring a 25% dilution of chlorine and dissolving the almost-impossible-to-dissolve CYA granules and exothermic CaCl flakes into buckets - where my main question about timing is about the dozen gallons of HCl mostly.

How long would you take to slowly incrementally add a dozen gallons of hydrochloric acid to a pool by hand?
Would you take a month? A week? A few days?

Never add more acid than it takes to reduce the pH to 7.2. The TA does not matter as long as the pH is 7.something

JamesW · Jul 30, 2024

Keep the pH at 7.2 and the CSI at 0.0.

The TA will slowly come down as you add acid to lower the pH.

There is no preferred timeframe.

It does not really matter how long it takes.

The time will really depend on how fast the pH rises, which depends on loss of CO2.

You can aerate to speed up the process, but there is no reason to try to accelerate the process.

JamesW · Jul 30, 2024

The amount of acid you can add will change and it depends on the TA.

As the TA comes down, the amount of acid you can add goes down.

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JamesW · Jul 30, 2024

If you had 50 ppm Borates, you could add more acid per dose, but there is no need to use borates.

Gary Davis · Aug 1, 2024

DrewLG said:
Your CSI can be in your target range with much less aggressive management of TA and CH than you are proposing.
And then, after the pool is filled, if you want to adjust CH higher and TA lower, you can do so slowly and gradually as you periodically add acid to counter the natural pH rise.
You'd want to keep your pH below 8 for other reasons, but just for correctness: Remember that with CYA in the water, pH has much, MUCH less effect on sanitation efficacy than without CYA. You've probably seen these graphs before -- the red lines (HOCl) are the important ones:

Thanks as that's all good advice, which I greatly appreciate given the total alkalinity is so high (the calcium isn't really a saturation problem in terms of controlling).

I've had this very high TA problem for many years since I refill the pool quite frequently with thousand-year-old well water (for reasons of saving the environment and my pocketbook), where the saturation calculation isn't a big problem since the TA is so high, it's rather easy to balance the water around +/- 0.3 at most temperatures that the pool will see (it will never freeze).

As for the Orenda charts - as you surmised - I've seen them all so I'm well aware of their philosophy of not chasing the pH. In fact, I've not only watched almost every Rule Your Pool video but Eric has been to my pool two years ago as we discussed the white precipitate that eventually comes out of the water in a fine powder which bubbles when acid is dropped into a small pile.

His recommendation, given that observation that even with the saturation numbers in sync, there was still a powder precipitate - simply because the TA was way out of range - was to give up on worrying about the saturation per se to first concentrate on lowering the TA to normal levels (and then, to worry about the saturation balance).

Eric said to control the calcium first and foremost, and then worry about the total alkalinity, where he commented off hand that people who don't have a super high TA in a big pool will never understand the problem because it's so difficult to resolve without massive amounts of acid - and because the calculations are inaccurate when concentrations are way out of normal ranges.

Gary Davis · Aug 4, 2024

JamesW said:
If you had 50 ppm Borates, you could add more acid per dose, but there is no need to use borates.

Thanks for that advice that borates allow more acid per dose, but the general rule I'm following is to get the TA under control first, as recommended in the borate thread, and even so, I had borates in the previous water and I wanted to get rid of them as I don't like the idea of once-a-borate-pool-always-a-borate-pool chemistry.

I've verrrrry slooooowly added a couple of cases of acid already, but I haven't fully filled the pool yet, so it's a titration & check method I'm using, where I'm getting a bit inventive (and somewhat lazy) in how I've been adding the acid (to lower the TA) and how I'm raising the pH as folks can see from illustrative photos I took today of the progress...

I'm going to open a separate thread on trying to find someone in the same boat that I'm in (high TA fill water) so I can glom off their experience, as it may be I'm doomed anyway given how far I have to go to get the TA anywhere near the "normal" range (and yes, I'm aware the +/- 0.33 saturation index can be met a million ways even with high TA).

Gary Davis · Aug 4, 2024

What is your fill water TA?
The reason I ask is I'm desperate to find someone in the same fill water situation that I'm in (very high total alkalinity of about 270ppm in a large pool).

In another thread we discussed how slowly to add massive amounts of acid (with aeration) to lower the TA in a large pool, where in this thread I'm simply asking to find SOMEONE (anyone!) who is in the same startup situation that I am in where the fill-water TA is so high that it's almost not worth trying to drop it to the "standard" range of around 100 ppm (give or take) just to get the saturation index into the +/- 0.33 non-aggressive/non-scaling range.

Is there anyone out there with the exact same problem?
How did YOU solve it?

The reason I think it's important to find someone with the same problem is that the solution seems so simple but it's expensive (and time consuming) and there may be a better way.

Of course, the most direct solution is:

Lower the TA with massive amounts of HCl (~12 gallons)
Simultaneously raising the pH with as much aeration as possible

But, as noted, that takes massive amounts of acid, where I could also wait for the monsoon season to fill the pool with low-alkalinity rainwater (but that isn't feasible at this point).
In addition, of course, I could have water trucked in - but that doesn't solve the cost problem as the costs are likely prohibitive and even then - I have to deal with the TA of that water.

I could do what I've always done prior, which is adjust for the saturation index with temperature without getting the TA into the normal range - but that ends up with calcium dust in the pool floor even with the saturation index being in the +/- 0.33 range (which Eric Knight tells me is likely because saturation calculations are increasingly less accurate when the ranges are off the scale).

In the end, with this thread, all I'm asking for is to find someone who has the same problem that I do - and to pick his brains as to how he solved the pragmatic problem of off-the-charts TA in a large pool.

mas985 · Aug 4, 2024

Gary Davis said:
Due to illness, the belated startup of my pool happened last week where for the saturation index (at the current 69 degrees Fahrenheit & 7.6 pH), I need roughly around 3 full HASA cases of 31.45% muriatic acid (to drop alkalinity from 270 ppm to 100 ppm) and just under about 50 pounds of calcium chloride (to raise calcium hardness from 290 ppm to 400 ppm), where my only question in this thread is how long would you take to add that amount of acid incrementally?

If I were in your situation, I would definitely not add any CH to the pool. Given it is very difficult to lower CH and you are trying to lower CSI, why raise it? 290 ppm is just fine for CH and a plaster pool.

Historically, we have had very high PH, TA & CH fill water so I am very opposed to adding CH unless it is very low. You can deal with CSI by just adjusting PH and TA. Keep PH at 7.2 until the TA drops for a reasonable CSI.

Gary Davis said:
I'm going to open a separate thread on trying to find someone in the same boat that I'm in (high TA fill water) so I can glom off their experience, as it may be I'm doomed anyway given how far I have to go to get the TA anywhere near the "normal" range (and yes, I'm aware the +/- 0.33 saturation index can be met a million ways even with high TA).

You really don't have far to go with lowering TA. With a TA 200 ppm and a PH of 7.2 will get you to a small negative CSI.

mas985 · Aug 4, 2024

I have responded here:

Swimming pool chemistry startup from well water - how slowly would you add ~3 cases of acid & ~50 pounds of calcium?

Due to illness, the belated startup of my pool happened last week where for the saturation index (at the current 69 degrees Fahrenheit & 7.6 pH), I need roughly around 3 full HASA cases of 31.45% muriatic acid (to drop alkalinity from 270 ppm to 100 ppm) and just under about 50 pounds of...

www.troublefreepool.com

But will repeat that historically, we have had high PH, TA & CH fill water. The only thing I have focused on is CSI. Target CSI to -0.3, keep PH >= 7.2 and ignore TA & CH except when determining CSI.

Just for reference, I am on the same plaster for almost 19 years now. So this methodology has worked quite well for me.

Lake Placid · Aug 4, 2024

Ending about 6 years ago I had worked for years at a seasonal commercial pool (300,000 gallons) that had 400-ish TA out of the tap. Yes we had a water slide to aerate the water and yes TA was adjusted with multiple carboys of acid over several days prior to opening to bring TA into a “more manageable range”. Once TA was reduced to a point we managed csi and let TA fall through PH management.

JoyfulNoise · Aug 4, 2024

Mark’s approach is probably the only pragmatic one in your situation. The only way to lower TA is with acid additions. So if you simply focus on keeping the CSI in the correct range, then the TA will naturally come down over time as you lower pH. In the beginning you will be adding acid almost daily. But as you get further along those additions will stretch out. You could install an acid feeder pump and simply use that to periodically add acid while monitor the pH using offline testing (I don’t recommend positive feedback control using a probe as that can be more trouble than it’s worth). Let the acid pump do the work and you simply change its dosing schedule as-needed.

Gary Davis · Aug 5, 2024

mas985 said:
I would definitely not add any CH to the pool. Given it is very difficult to lower CH and you are trying to lower CSI, why raise it? 290 ppm is just fine for CH and a plaster pool.

That's a good point. Thanks for that sound advice. It's good to get another take on the situation.

Your point is that I'm maybe fixated on the wrong metrics. I do have chronic calcium dusting though - even with the saturation index in the green, which I think might be due to the TA being so far in excess of the normal range that the calculations might not be accurate.

However, it's worth noting I belatedly agree with you that LOWERING calcium is much harder than dealing with TA (which is easy, by way of comparison, to lower or raise).

mas985 said:
Historically, we have had very high PH, TA & CH fill water so I am very opposed to adding CH unless it is very low.

I'm curious what your TA numbers are of your fill water.

mas985 said:
You can deal with CSI by just adjusting PH and TA. Keep PH at 7.2 until the TA drops for a reasonable CSI.

My pH is normally 7.6 or above, as it's rarely at 7.2 unless I'm adding acid (which I do to lower the TA).
Of course, the problem with lowering the TA is the massive amount of muriatic acid it requires (three full HASA cases).

mas985 said:
You really don't have far to go with lowering TA. With a TA 200 ppm and a PH of 7.2 will get you to a small negative CSI.

I like your advice which sounds reasonable for me to get both the calcium and total alkalinity, if not in the perfect range, at least in a closer range to what most of the calculations use.
Thanks for the kind advice. Much appreciated.

JamesW · Aug 5, 2024

Definitely do not add calcium.

The pH has to be kept down as much as possible to keep the CSI below +0.3.

The TA should be down to about 110 by now, right?

mas985 · Aug 5, 2024

Gary Davis said:
Your point is that I'm maybe fixated on the wrong metrics. I do have chronic calcium dusting though - even with the saturation index in the green, which I think might be due to the TA being so far in excess of the normal range that the calculations might not be accurate.

Are you using LSI or CSI? CSI is the better metric to use.

Gary Davis said:
I'm curious what your TA numbers are of your fill water.

It varies year to year and time of year as well. Our city uses several wells in addition to surface water. I have an older report from 2022 which shows TA average at 255 ppm and a CH average of 387 ppm. The current levels are much lower because the city had to shut down a couple of wells due to PFAS levels. I took advantage of this last December and replaced the 800 ppm CH water with 150 ppm CH & 100 ppm TA water.

Gary Davis said:
My pH is normally 7.6 or above, as it's rarely at 7.2 unless I'm adding acid (which I do to lower the TA).
Of course, the problem with lowering the TA is the massive amount of muriatic acid it requires (three full HASA cases).

I like your advice which sounds reasonable for me to get both the calcium and total alkalinity, if not in the perfect range, at least in a closer range to what most of the calculations use.

I would ignore the ranges of the individual components of CSI, except at the extremes, and focus just on CSI. That is what really matters for a plaster pool.

Flying Tivo · Aug 5, 2024

Gary Davis said:
I greatly appreciate given the total alkalinity is so high

TA is usually high for Well waters in general. Dont rush, TA is not that important in general and in the short term. Chlorine and Ph as said before are the important ones.

Gary Davis · Aug 8, 2024

JamesW said:
Definitely do not add calcium.

Thanks for that advice to hold off on the calcium salt additions.

I've slowly added two of the three HASA cases of muriatic acid, but I'll stop adding calcium chloride as my current hardness readings are about 230 ppm, which is at least within the normal ranges.
TDS reads at 700 and all the metals and phosphates are 0 ppm (which is typical for my well water which is hundreds of years old when it comes out of the ground).

JamesW said:
The pH has to be kept down as much as possible to keep the CSI below +0.3.

The pH fluctuates but on my last test today it was 7.7 (which is at least below the pH ceiling based on the carbonate alkalinity).
Of course, it's hard to keep the pH down when you're adding massive amounts of HCl; but the 24-hour bubbling from the reverse-fitted rock-weighted shop vac may be helping.

JamesW said:
The TA should be down to about 110 by now, right?

The total alkalinity readings are about 160 ppm (and I raised the CYA to 30 ppm, which is slightly higher than what I want but there's still six inches to go).

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