My water source is TA 240 ppm, should I adjust it before adding borates?

[owkaye]

Last year when I first filled my pool, I brought my TA down from 240 to 80 ppm so I could add 50 ppm borates to help stabilize my TA and pH for the entire season. This 80 ppm TA level was recommended by someone as being a good level to start with when adding borates, so I followed that person's advice. I still had to add acid every few days to keep my pH at 7.5, so the borates did not stabilize my pH at 7.5 as I thought they might. But my TA did not change all summer after the borates were added.

Yesterday I learned about Ben Powell's "high pH pool" theory and it made me wonder if I wasted my time/money last year adding acid every few days just to keep my pH at 7.5 all season? Perhaps if I had just let my pH go rather than constantly adjusting it, it might have stabilized on its own in the 7.8 - 8.0 range, which according to Ben would have been just fine!?

I recently filled my pool again with the same source of TA 240 ppm water as last year. But this time I wonder if I should just "leave my TA alone" and add the 50 ppm borates as soon as I get my pH into the correct range? If I add borates at such a high TA will they keep my TA stable at 240 this year?

And how will this affect my pH levels? Will my pH keep climbing all season in an attempt to reach equilibrium with my high TA? Or will the borates be able to buffer my pH enough to keep it more stable than last year, and possibly reduce my need to add acid frequently?

 

[needsajet]

You'll want to read this first... Borates - Why and How

High pH is tricky due to the reduced effectiveness of FC. You should read at least the first page of this... Pool Water Chemistry and be sure you understand the relationship of pH and active vs. free chlorine.

You can take your TA a fair bit lower than 80 to reduce the frequency of acid additions, depending on the rest of your numbers. If it was me, I'd work the TA down and try to find the sweet spot for your pool before adding borates.

If you go for high pH management, I'm interested to hear how you go.

 

[JoyfulNoise]

Your problem is your fill water. I'm guessing at 240ppm TA it also has a fairly high pH (8+). Also, 7.5 is an unreasonable pH for most pools. In your situation you'd be better off reducing TA and then targeting a 7.6-7.8 range. My fill water has a TA of 120ppm and a pH of 8.2. With my pool TA at 60ppm and 50ppm borates, I add acid about every 10 days or so. I target a pH of 7.6 and my pH will rise and hang at 7.7 for those 10 days. If I lower it to 7.5 it will pop up to 7.6 in less than 24 hours.

If you add borates to 240ppm pool water, you'll create a problem. It will take huge amounts of acid to lower the pH even to 7.8. At 240ppm TA, your pool water will likely stabilize at 8.2-8.4. That will put you at risk of calcium scaling unless you keep your CH very low. It will also make your active chlorine less effective as a greater proportion of it will be hypochlorite anion (OCl-) rather than hypochlorous acid. You may even notice a greater chlorine demand because OCl- is more reactive to UV loss. If you do run high TA/high pH, then forget about borates all together. They won't be of much use.

I'm not sure how much actual pool data Ben compiled on that high pH theory. You can certainly try it out for a season but you may not find water in the low 8's all that comfortable and scaling (calcium and metals) will always be a concern.

 

[owkaye]

7.5 is an unreasonable pH for most pools. In your situation you'd be better off reducing TA and then targeting a 7.6-7.8 range.

This probably explains why I found myself adding acid so frequently last year. I'll give your suggestion a try.

My fill water has a TA of 120ppm and a pH of 8.2. With my pool TA at 60ppm and 50ppm borates, I add acid about every 10 days or so.

This sounds better than adding acid every 2-3 days like I did last year.

I target a pH of 7.6 and my pH will rise and hang at 7.7 for those 10 days.

Do you think your pH might stay at 7.7 for a month or more without adding more acid? Or is 10 days the point at which your last acid addition is "used up" and you need to add more to prevent your pH from climbing to 7.8 or higher?

If you do run high TA/high pH it will also make your active chlorine less effective. You may even notice a greater chlorine demand.

I don't necessarily want to run a high-pH pool, nor do I want to increase my chlorine demand.

Based on your reply so far, it seems I should have brought my TA down even lower than 80 last year. I could bring it down to 50 or 60 this year before I add borates, and see how it works out. Or should I bring it down to 40 or 30 and then add the borates? What are the consequences of starting with such low TA levels?

Thanks JoyfulNoise, I appreciate learning from your experience.

 

[pooldv]

Low TA, below 50, does not leave enough alkalinity to buffer your PH and can lead to rapid PH crashes. I wouldn't go below 50. Try 60 first and see how long you PH will stay at 7.8.

 

[JoyfulNoise]

I doubt my pH would hold for a month. I longest I've gone is about 15 days and it was at 7.8. I have acid demand drops so I can titrate the pH test a little and I knew it was on the high side of 7.8, probably closer to 8.0. I don't like letting my pH get up to that level because I have very high CH so I need to keep my CSI negative or as close to 0 as I can.

If the process of lowering your TA is not too much of a hassle, then try 60ppm. You should see a greater effect. Part of the problem is fill water. So I would suggest, if you can, cover your pool or control evaporative water loss to minimize the need to use fill water.

 

[owkaye]

Low TA, below 50, does not leave enough alkalinity to buffer your PH and can lead to rapid PH crashes.

That doesn't sound good.

I wouldn't go below 50. Try 60 first and see how long you PH will stay at 7.8.

Will do ... and thanks!

 

[owkaye]

Part of the problem is fill water.

Right ... because every time we add more water it's going to increase the TA and pH thus requiring more acid.

If you can, cover your pool or control evaporative water loss to minimize the need to use fill water.

Fortunately we had a very easy-to-use cover last year, and most of the time it was on the pool. We're not so lucky this year because we do not have a cover yet, and the pool gets a lot more sun this year, too.

I'll continue adding acid and aerating until I get the TA down to 60 and the pH up to a safe swimming range. Then I'll add my borates and hope for the best.

Thank you all for everything you've helped me with in this thread.


... and just one more question while I'm thinking about it: Typical groundwater generally has a lower TA than municipal tap water, correct? The reason I ask is because I have a deep water well that I can use to add water to the pool (after I get the pump hooked up again), and maybe the deep well water has a lower TA than my tap water.

 

[JoyfulNoise]

Not always. There are areas of the country where well water can be over 300ppm TA. Depends on the source and geology of the aquifer. Municipal supplier will actually try to lower/control the TA of their water supply to reduce scaling in distribution pipes.

 

[owkaye]

Not always. There are areas of the country where well water can be over 300ppm TA. Depends on the source and geology of the aquifer. Municipal supplier will actually try to lower/control the TA of their water supply to reduce scaling in distribution pipes.

Heh. I was thinking that municipalities would try to raise TA so their water wouldn't be so acidic that it eats through old iron distribution pipes. But it seems some of them have just the opposite problem.

I'll definitely check the TA of my deep well water if I ever get the pump fixed/replaced and hooked up again.