Can't lower alkalinity

[selgd]

Hello! I've had a salt pool (vynil lined) for a year now. We always had trouble with lower pH around 6.9, but otherwise we had no issues. We kind of neglected the pool during 6 weeks last winter and the water turned green. The pump wasn't enough to clear it so we added some chlorine. After that the pH started going completely crazy, pH ranging from 3 to 10, and we called the pool store. They came, said the alkalinity was low and corrected it. But since then (November) alkalinity is ALWAYS low. We've already added 20 kg (44 lbs) of baking soda and alkalinity always ends up between 10 and 40. We've been adding half of what's needed according to the calculators, stopping the pH dosification, and adding the rest after a couple of days, but it only goes to 60 or 70 and then it lowers again. I found a different formula that tells the maximum amount of product to add, so now I'm adding 200-400 mg daily and I still can't get the alkalinity above 70 ppm several hours after adding baking soda, 30 the next day. Is a 31 m2 pool and it's covered. Water temperature is between 23 and 30 C°. I'm very tired of having to add baking soda everyday and the alkalinity is always low, the pH is always crazy. What am I doing wrong? I'm desperate.

 

[Texas Splash]

Welcome to TFP! So there are a few things to discuss in your situation:
1 - How are you testing your water. In your country you probably won't have access to our TF-100 Series kits or a Taylor K-2006C, so what exactly do you use?
2 - Water doesn't just become that acidic unless something is making it do so. Are you adding acid products? Are you using chlorine tablets on a daily basis?
3 - Have you ever tested your fill water? Do you fill from city water or a well?
4 - Take a moment to update your signature with all of your pool and equipment info. It will help with replies.

Also be sure to bookmark our Pool Care Basics page for lots of great info. You can also download the PoolMath APP which is a nice tool as well.

Let us know if you have any questions.

Create Your Signature - Further Reading

www.troublefreepool.com

 

[selgd]

Welcome to TFP! So there are a few things to discuss in your situation:
1 - How are you testing your water. In your country you probably won't have access to our TF-100 Series kits or a Taylor K-2006C, so what exactly do you use?
2 - Water doesn't just become that acidic unless something is making it do so. Are you adding acid products? Are you using chlorine tablets on a daily basis?
3 - Have you ever tested your fill water? Do you fill from city water or a well?
4 - Take a moment to update your signature with all of your pool and equipment info. It will help with replies.

Also be sure to bookmark our Pool Care Basics page for lots of great info. You can also download the PoolMath APP which is a nice tool as well.

Let us know if you have any questions.

Create Your Signature - Further Reading

www.troublefreepool.com

Thanks for your answer! I just updated my signature, I'll copy it here and answer your questions.
Signature: 8250 gal, polyester + vinyl ester, 1.5 HP kripsol ks evo vs pool pump, Star-plus 500 sand filter (187 lbs), Bayrol Automatic SALT electrolysis system, polycarbonate semitransparent semi-high telescopic cover, Hanna alkalinity checker HI 775.

1. I'm using Hanna instruments electronic alkalinity checker for alkalinity, and for pH I just look at the salt chlorine generator screen. Sometimes I do stripes but they always show the same values than the screen.
2. I am not adding anything acidic, I don't add chlorine tablets since November. The pool has automatic ph-minus administration, but I turn it off every time I add baking soda regardless of the pH values. When I'm not adding baking soda and it's on, it turns off automatically when the pH is below 7.5. but it still continues to go lower and lower.
3. I fill from city water, alkalinity is 240, ph 7.2

Thank you!

 

[Texas Splash]

Something is odd for the city water source to have a TA of 240 and your pool so low. Very odd if you're not adding acid. I hope that pH-minus administration you spoke of isn't somehow malfunctioned. Either that or perhaps there's a problem with the test equipment you are using. I'm not familiar with those products, but with a fill water of about 240, your pool's TA level should easily be more elevated than what you described in your first post. The pH would also rise more as well.

To make sure I'm not missing something obvious, I'm going to ask @Donldson for another opinion. Stand by ..................

 

[selgd]

Something is odd for the city water source to have a TA of 240 and your pool so low. Very odd if you're not adding acid. I hope that pH-minus administration you spoke of isn't somehow malfunctioned. Either that or perhaps there's a problem with the test equipment you are using. I'm not familiar with those products, but with a fill water of about 240, your pool's TA level should easily be more elevated than what you described in your first post. The pH would also rise more as well.

To make sure I'm not missing something obvious, I'm going to ask @Donldson for another opinion. Stand by ..................

Thanks for your time!
I thought the pH-minus could be doing something wrong and now I'm mostly turning it on and off manually depending on pH levels. Yesterday morning I had a TA of 70 and pH 7.5, I added 300 mg of baking soda (I think that's like 0.011 oz) and pH today was 9.7, so I turned on ph-minus administration for like an hour, until pH was 8. I measured alkalinity and it was 60 . I tried ignoring alkalinity in case the testing was wrong, but if it goes lower than 40 I start to have pH measurements ranging between 3.3 and 10 within the same day. So basically I feel stuck in the endless circle of high pH ok TA, I lower pH, and TA lowers tremendously, have to increase TA, wait one or two days and pH is still super high, have to lower pH, TA lowers... And it's been 8 months of this nonsense. I basically have to add baking soda 2-4 days per week. I attached the screenshot of current parameters. I don't know if I should just let pH skyrocket and wait, or continue to add pH-minus and lose TA. Or just empty the pool and start over but honestly I would rather not do that if there was a solution to this.

 

[Texas Splash]

It is odd. I've never seen anyone's TA just fall like that, ot have to add so much baking soda to their water unless it was receiving acid. Makes no sense here. My only thought is the testing itself and wondering if the tester you are using is calibrated and proving you with the correct response. That or the reagents themselves.

 

[Bperry]

Thanks for your time!
I thought the pH-minus could be doing something wrong and now I'm mostly turning it on and off manually depending on pH levels. Yesterday morning I had a TA of 70 and pH 7.5, I added 300 mg of baking soda (I think that's like 0.011 oz) and pH today was 9.7, so I turned on ph-minus administration for like an hour, until pH was 8. I measured alkalinity and it was 60 . I tried ignoring alkalinity in case the testing was wrong, but if it goes lower than 40 I start to have pH measurements ranging between 3.3 and 10 within the same day. So basically I feel stuck in the endless circle of high pH ok TA, I lower pH, and TA lowers tremendously, have to increase TA, wait one or two days and pH is still super high, have to lower pH, TA lowers... And it's been 8 months of this nonsense. I basically have to add baking soda 2-4 days per week. I attached the screenshot of current parameters. I don't know if I should just let pH skyrocket and wait, or continue to add pH-minus and lose TA. Or just empty the pool and start over but honestly I would rather not do that if there was a solution to this.

The pH minus device lowers both ph and TA by adding acid. Baking soda raises the TA with little effect on pH.

Have you tried turning off all the dosing equipment and just getting your TA to 50 and your pH to 7.8? Those are the ideal parameters for most around here and result in pretty stable water.

 

[Bperry]

Yesterday morning I had a TA of 70 and pH 7.5, I added 300 mg of baking soda

There was no need to do that. A TA of 70 is fine. Adding the baking soda makes the pH go up faster. It does sound like you have an equipment issue though.

 

[selgd]

The pH minus device lowers both ph and TA by adding acid. Baking soda raises the TA with little effect on pH.

Have you tried turning off all the dosing equipment and just getting your TA to 50 and your pH to 7.8? Those are the ideal parameters for most around here and result in pretty stable water.

Hi! No, I thought I needed higher TA. I'm going to try to maintain those levels and see what happens. Thanks!

 

[Mdragger88]

I would leave the acid doser off for now as suggested & manually add what you need (if you actually need it)
Then test to see what your doser is actually doing to determine if it’s overdosing or getting improper readings etc.
Most find automatic ph sensors with acid dosers to eventually be more of a headache than a help as they need a lot of maintenance to operate properly.
See

What Are My Ideal Pool Levels?

 

[Bperry]

Hi! No, I thought I needed higher TA. I'm going to try to maintain those levels and see what happens. Thanks!

As the TA gets lower it makes the pH a bit more unstable so dont let it get below 40-50. As the TA rises, the pH will want to rise even faster which creates an endless cycle so dont try to force the pH too low either. If the pH gets up to 8.2, then drop it back down to 7.8 at most. See how that does.