Having a hard time stabilizing pH

[stev32k]

The pH in my pool is constantly rising and I've had to add almost 1 gal (122 oz) of concentrated HCL in the past 7 days. The TA was running 60 ppm so I tried to lower it by adding acid to get a pH of 7.2. Three ago I added 40 oz of concentrated HCL and that brought the pH down to 7.2 and reduced TA to 40 ppm. This morning the pH is 7.6 and the TA is back to 60.

Yesterday I added about 1/4" (~ 125 gal) of water to the pool to make-up for evaporation. Test results this morning are:

FC 4.0
CC 0
pH 7.6
TA 60
CYA 40

City water that is used to fill the pool contains about 20 ppm TA. There is no aeration of the pool water only a swirl at the surface from the returns. So, is the acid use something I have to live with or is there some way reduce its use?

 

[Defgufman]

I found that 90 TA was better for stabilizing my PH.

 

[stev32k]

I should add that before my liner was replaced in March this year I had a small leak in the pool for several years. During that time I found that a TA of 50 or more would require acid addition about every other week to maintain a pH of 7.4 to 7.8. When the TA dropped to 40 the pH stabilized at 7.5 and would stay there for at least 2 months. Since the pool no longer leaks maybe I should raise the TA to the 70 - 80 ppm range?

 

[duraleigh]

Yes, I think you will get some additional stability as defgufman says. You do not have an SWG, correct?

 

[stev32k]

Yes, I think you will get some additional stability as defgufman says. You do not have an SWG, correct?

No, I don't have a SWG. I just raised the TA to 80 and will watch if for a few days to see what effect that has.

 

[onBalance]

Stev32K, In general, raising the TA to 80 ppm will cause the pH to rise higher and faster than when maintaining a lower TA of 40 ppm - exactly as you experienced previously.

 

[prs]

Your pool might want to stabilize at a pH closer to 7.8, all pools are different. Why not just stop adding acid and then test every day or two until it stops rising?

My pool likes to stay in the 7.8 to 8.0 region. I can add acid until I'm blue in the face and the pH will rise to 7.8 in a couple of days, it will then stay between 7.8 and 8.0 for weeks before I have to add acid again. My TA is 70.

 

[pooldv]

Maybe adding Borates will help. More info here, http://www.troublefreepool.com/threads/90257-Borates-Why-and-How

 

[stev32k]

I would like to keep the pH at 7.5 - 7.6 because chlorine is more effective in that range. I raised the TA to 80 on Monday (yesterday) then brought the pH down to 7.5. I'll watch it for a few days and see what happens.

If that does not work out I'll drop the TA to 40.

 

[Patrick_B]

Normally, that is correct, but Cya pushes that window open a lot wider, so that pH is not nearly as limiting a factor. If you don't have CSI issues to worry about, that is a great range. Even up to 7.8 is good with Proper Cya levels.

 

[stev32k]

Normally, that is correct, but Cya pushes that window open a lot wider, so that pH is not nearly as limiting a factor. If you don't have CSI issues to worry about, that is a great range. Even up to 7.8 is good with Proper Cya levels.

I see you caught the discrepancy in recommended TA levels. I was about to ask about that.

 

[Patrick_B]

Ask away

 

[stev32k]

I was going to say I like your 30 - 60 ppm range better than the 70 - 90 ppm range I see elsewhere on the site. At least my pool seems to stabilize better in the 30 - 60 ppm range. When ever I've tried to raise TA over 50 ppm I have to start adding HCL like crazy.

 

[Patrick_B]

Where do you see 30-60?

 

[stev32k]

It's gone now.

 

[Patrick_B]

Borates can push the lower window open for you a little as well. You can run 40 with Borates, just be mindful that CSI is a log scale instead of linear. People forget that about pH too.

 

[Defgufman]

As to not hijack this thread I'll start a new one, but the CSI Is still a mystery to me.

 

[Patrick_B]

Got it covered.