Alkaline & PH very low

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Thailand Steve

Member
Dec 5, 2023
24
Thailand
Pool Size
29000
Chlorine
Salt Water Generator
I’ve had my pool for over 6 years and never had an issue with low PH before.
In the last week, my PH levels have dropped to between 5 and 6 ppm.
I added 5 pounds of soda ash (29,000 gallon pool) and the PH appeared to be coming back up nicely.
When my pump stopped circulating last night, the PH on my dousing pump (in stop mode) was reading 7.4 ppm.
I wake up this morning and checked again once the pump started and I see sub 6 ppm again.
I checked the alkaline level and found this to be basically zero. I then added 5 kg of baking soda, giving me about 45 ppm on my alkaline test kit (will add more tomorrow).
My PH is still very low and that was doing 2 different manual tests plus my dousing pump reading.
Do I just keep adding more soda ash?
I’m running a salt water chlorinator and tend to keep my levels around 2 ppm +, which has never been an issue before.
Would really appreciate some advice, as getting experience help/advice locally is just not available.
 
Thailand Steve said:
I’ve had my pool for over 6 years and never had an issue with low PH before.
In the last week, my PH levels have dropped to between 5 and 6 ppm.
I added 5 pounds of soda ash (29,000 gallon pool) and the PH appeared to be coming back up nicely.
When my pump stopped circulating last night, the PH on my dousing pump (in stop mode) was reading 7.4 ppm.
I wake up this morning and checked again once the pump started and I see sub 6 ppm again.
I checked the alkaline level and found this to be basically zero. I then added 5 kg of baking soda, giving me about 45 ppm on my alkaline test kit (will add more tomorrow).
My PH is still very low and that was doing 2 different manual tests plus my dousing pump reading.
Do I just keep adding more soda ash?
I’m running a salt water chlorinator and tend to keep my levels around 2 ppm +, which has never been an issue before.
Would really appreciate some advice, as getting experience help/advice locally is just not available.
Click to expand...
I assume the pH dosing pump is for acid? And it’s now off, correct?

If I had to guess it would be that dosing acid to reach pH 7.4 is too aggressive because it’ll keep lowering the TA along with it, which will then cause the pH to become unstable if TA gets below 50ppm. You’de be better off dosing pH to ~7.8.

You need a TA well above 50ppm and a pH above 7.0. Get the TA up where it needs to be and then boost the pH.

The chlorine question is totally dependent on your CYA level. 2ppm might be ok if you have zero CYA but it’s way too low if you have CYA 50ppm.
 
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Thanks for the reply.
Sorry, yes it’s an acid dousing pump and I’ve had it now for a couple of years.
Never been particularly happy with it as it never seems accurate and it has pumped too much acid in before.
Never to lower the PH to where it has been recently though.
I work away from home quite often and it’s either the dousing pump or my so called pool cleaner that either puts too much acid or not enough.
I spent a lot of time checking the PH with manual test kits and setting my dousing pump up in line with that. Normally always around 7.7/7.8, like you suggested.
Yes my alkaline levels were almost zero but I’ve had low alkaline levels before and my PH has never dropped drastically like that in the past.
In fact for the first few years of having this pool, nothing was added at all, other than salt or acid because that is all the pool cleaners know what to add here.
You mention alkaline or cyanuric acid and they have no idea what you’re on about.
So during these first few years, I guess I got lucky, as I had very few issues.
Regarding chlorine, sorry that was a typo, it should have been 3 ppm not 2.
You had me thinking about the cyanuric acid, as I haven’t added any of that for more than 6 months. Checked that with test kit and its also zero!
I’ve added another 4 kg of baking soda this morning. Will let that circulate for few hours then check again.
I bought another 2 x 2 lbs bags of soda ash this morning also, so I’m ready to add some of that later if the PH is still low.
I have a 5 kg bucket of cyanuric acid but will wait a day or 2 before adding that, as it may throw my PH off again correct?
 
Thailand Steve said:
Thanks for the reply.
Sorry, yes it’s an acid dousing pump and I’ve had it now for a couple of years.
Never been particularly happy with it as it never seems accurate and it has pumped too much acid in before.
Never to lower the PH to where it has been recently though.
I work away from home quite often and it’s either the dousing pump or my so called pool cleaner that either puts too much acid or not enough.
I spent a lot of time checking the PH with manual test kits and setting my dousing pump up in line with that. Normally always around 7.7/7.8, like you suggested.
Yes my alkaline levels were almost zero but I’ve had low alkaline levels before and my PH has never dropped drastically like that in the past.
In fact for the first few years of having this pool, nothing was added at all, other than salt or acid because that is all the pool cleaners know what to add here.
You mention alkaline or cyanuric acid and they have no idea what you’re on about.
So during these first few years, I guess I got lucky, as I had very few issues.
Regarding chlorine, sorry that was a typo, it should have been 3 ppm not 2.
You had me thinking about the cyanuric acid, as I haven’t added any of that for more than 6 months. Checked that with test kit and its also zero!
I’ve added another 4 kg of baking soda this morning. Will let that circulate for few hours then check again.
I bought another 2 x 2 lbs bags of soda ash this morning also, so I’m ready to add some of that later if the PH is still low.
I have a 5 kg bucket of cyanuric acid but will wait a day or 2 before adding that, as it may throw my PH off again correct?
Click to expand...
Yep, any acid will lower the pH. And you should never let the TA get below 50 or the result is typically pH crashing. Not sure how you got along so far along without that happening.

What is your refill water test like? Or is it mostly rain?
 
Acid dosers need periodic replacement of several parts - perhaps its time to do some maintenance on yours?
How does it operate? Do you manually set it to dole out a specific amount of acid or does it have a sensor?
Check the fill water ta & ph so you know what you’re working with as well.
As Bperry mentioned, aim for ta of 50/60 with baking soda now (ph should rise then with some aeration)
& target ph in high 7’s when dosing with acid to prevent crashing ta inadvertently.
After you get the ta & ph up then use the sock method for cya. Cya of 60 will help your swcg to have to work less thus extending its life. Many go to 70/80 in the peak of summer.
Be sure to increase fc with liquid chlorine to accommodate for the cya increase
FC/CYA Levels
then just set the swcg to produce what you expect your daily loss to be. (Average is 2-4ppm/day)
Use PoolMath effects of adding tab to see the ph consequences of the cya addition.
Please fill out your signature with all your equipment (test kit, acid doser type, swcg brand & size etc)
We can assist with setting up swcg if we have the details

Create Your Signature - Further Reading

www.google.com www.google.com
 
I’ve just recently replaced the sensor on my acid dousing pump. That’s actually the 3rd sensor in the past few years. Its Emaux brand and parts are ridiculously expensive here. I want to bin it but due to the money spent, that’s hard..
I’ve calibrated multiple times and never get it to match the manual test kits.
This morning my Alkaline was between 40 and 50 so I added another 1 kg of baking soda. PH was still struggling to stay above 7 ppm after being way above the night before.
I tested my water supply and it’s 100 ppm for alkaline and around 7.7 ppm for acid so no issue with that.
When my pump came on again this afternoon, I added 2lbs of soda ash. After a few hours I re-tested, now I have 7.4 for acid (digital reading on dousing pump says 7.8) and my alkaline is sitting around 60 ppm.
My pool is an infinity type, so I have no skimmer. The developers never put an overflow line in either so at first, during heavy rain, my garden was getting flooded with salt water (killing my plants).
I later installed a submersible pump in to my pool holing tank. This has a sensor that kicks in to stop the tank over flowing. Only problem with that is, it dumps water from bottom of the tank (with the correct chemicals) instead of the rain water on the top.
I keep this pump off as much as I can but when it’s heavy rain season, the balance in my pool chemistry is all to pot.
Not ideal and if anybody can suggest a better solution, I would love to hear it.
The tank is flush with my garden and below the level where the pool water overflows in to. Stupid design….
I’ve not added cyanuric acid yet as I’m still not comfortable with my PH. Will look at that tomorrow.
 
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You are doing more work fighting against your automatic pH system then if you turned it off, let your pH and TA settle down, did manual pH testing and adding acid only when your pH hit 8 to reduce it to 7.6.

Stop adding baking soda or soda ash and let your TA and pH drift up.
 
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My acid dousing pump has been in the off position for days now, if you had read my earlier post.
Understand my alkaline was at zero and my PH was way down there (under 5 ppm at one point) just a few days ago. Leaving it alone as you say, would not have been the best option right?
Now I think I have balanced things out a bit better, I will be leaving things to stabilise for a bit.
 

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As per previous post:

When my pump came on again this afternoon, I added 2lbs of soda ash. After a few hours I re-tested, now I have 7.4 for acid (digital reading on dousing pump says 7.8) and my alkaline is sitting around 60 ppm.
 
If your dousing pump thinks pH is 7.8 when it is 7.4 no wonder you have had problems.

That is why we don’t recommend automatic pH systems.

PH of 7.4 and TA of 60 is perfect. Don’t add any more chemicals until your pH hits 8 and then only acid to lower it to 7.6 and not lower.
 
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I’ve had this pump for a few years and have set the PH as per my manual tests. Never before has my PH dropped so drastically as it has recently.
Had years of heavy rain, years of me being away overseas and not being able to check things, years of an incompetent pool cleaners etc etc but never this massive drop in PH.
This is what’s troubling me
 
Thailand Steve said:
I’ve had this pump for a few years and have set the PH as per my manual tests. Never before has my PH dropped so drastically as it has recently.
Had years of heavy rain, years of me being away overseas and not being able to check things, years of an incompetent pool cleaners etc etc but never this massive drop in PH.
This is what’s troubling me
Click to expand...
I think if you leave it off for now it may help things stabilize. Depending on how long you leave overseas, you may not need a pH doser. I’m pretty amazed at how well trichlor pucks in a floater hold the pH steady,
 
Thailand Steve said:
What does that mean? Regarding your last sentence ?
Click to expand...
I had my pool replastered a couple months ago. Normally people seem to see very aggressive pH rise with new plaster for quite some time, but my pH is fairly steady in that I haven’t needed to add acid in over a month. Since it’s all new water, pretty cold (no SWCG in winter) and, without any CYA, I’ve been chlorinating with trichlor pucks in a floater. I suspect my stable pH is being helped by the acid in the trichlor dissolving slowly over the past couple months.

If you have access to trichlor(without copper in it) that might be an option to help you out, especially since you sound like the climate gives you a lot of make up water that would help avoid building up too much CYA over time. You may have to adjust the SWCG down a bit and there may be other considerations that make that problematic.
 

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