Soda ash not effective

[basjke]

Yesterday I arrived at me ex her place who has a pool of approximately 30.000 liter. I noticed that the water was cloudy and she told me that her boyfriend just had poured 4kg of Soda ash lite in the pool.
I thought that's gonna be funny, as 4kg in that size of pool would raise the pH probably through the roof.

Today I went back with my digital pH tester and aquachek teststrips and expected to see some big problems.

I was surprised that the water was very clear, and tested only pH6.5.

Alkalinity was about 70, chlorine 0 and CYA over 150ppm. I knew about the CYA problem before and had warned her already.

It took me another 3kg of soda ash to get the pH to 7.3, which is definitely not normal.

Tested again and now TA was somewhere between 120 and 180ppm, but I expect more to the high end, and CYA of course over 150.

What can be the cause that the Soda ash doesn't register the way it should.

Could it be the high level of CYA or is Soda ash lite actually baking soda or something?

 

[JasonLion]

Most likely they have been adding chlorine with either trichlor or dichlor, both of which are very acidic and raise the CYA level, and not adding anything to maintain the PH. So the PH ended up getting very very low, and CYA ended up very high.

 

[Patrick_B]

Are you certain the pH meter was right? I don't trust the strips reading, but I'm curious about the meter.

 

[basjke]

The pH meter was 3 point calibrated right before I tested, and the Aquachek silver strips, confirmed the result. I also use the meter in my own pool which has a Zodiac Tri pH, because I ran out of calibration solution for the Zodiac and wanted to be sure the reading was correct. The meter and the Zodiac give the same reading given or taken 0.1.

I know the CYA is extreme high, so I thought maybe that could affect the effectiveness of the soda ash?

 

[Patrick_B]

The Cal solution is fine for either probe. It sounds like you got a good reading with a solid 3 point cal.

I think the Soda should overcome the pH issue, so I would lean toward some other variance assuming the reading was correct.

 

[basjke]

The Cal solution is fine for either probe. It sounds like you got a good reading with a solid 3 point cal.

I think the Soda should overcome the pH issue, so I would lean toward some other variance assuming the reading was correct.

The calibration solution that come with the hand held pH tester ar 4.0 -7.0 and 10.0 while the Zodiac needs a single calibration solution of 7.5.Not sure if there is an easy way to create 7.5 solution with the liquids I have.

I started with adding 500 gram to the pool, which should have given a significant increase,but in fact didn't do anything. So I added a little to just a bucket of water, and that tested right away something like 12.0, so it was clear that it was indeed soda ash.

But I ended up to add 3 kg to increase the pH with 0.8, which is not normal for sure, while with the TA increased by something like 100 at the same time.

 

[Patrick_B]

That is certainly new to me. I've seen many, many different brands of pH controllers, lab desktops, etc. I've never even heard of a 7.5 pH solution so perhaps it's a foreign thing. Very unusual.

Being honest, and after a review of your information, I'm at a loss to explain what's happened there, I'm sorry.

 

[DHoover85]

Try aeration to "convert" your slightly high TA into a slight rise in PH. But you will want to do a partial drain/fill to lower that CYA down to something manageable.

 

[basjke]

That is certainly new to me. I've seen many, many different brands of pH controllers, lab desktops, etc. I've never even heard of a 7.5 pH solution so perhaps it's a foreign thing. Very unusual.

Being honest, and after a review of your information, I'm at a loss to explain what's happened there, I'm sorry.

Zodiac is Australian isn't it. I ordered the unit from Australia by the way.

I will go test the pool again this afternoon and keep updated.

- - - Updated - - -

Try aeration to "convert" your slightly high TA into a slight rise in PH. But you will want to do a partial drain/fill to lower that CYA down to something manageable.

I understand how to reduce the CYA and how to increase pH by aeration, but the question is actually why the soda ash doesn't register in the water.

7kg in total of soda ash in a 30.000 liter pool would raise pH with something like 6.7. I doubt that the pH was 1.0 to start with because that would make the tiles float at the surface.

 

[basjke]

I just notice something strange in the pool calculator, maybe someone can explain.

If I set the pool to 30.000 liter and TA at 100, and enter that current pH is 6.5 and the goal 7.3, it says I need 2,2 kg of soda ash.

Now if I enter in the "effects of adding chemicals" tab that I will add 2300 gr of soda ash, it tells me that the pH will increase by 2.22

 

[Patrick_B]

You know, I'm not sure. Never even heard of such a pH buffer, so it may be their own thing.

Just out of curiosity, can you get hold of another pH source for testing? Like a phenol red test or even some good pH strips that measure pH only?

 

[jblizzle]

Read the disclaimer in the effects of adding pool chemicals section. You can not use it like you are trying to use it.

 

[JasonLion]

I feel like I am missing something. Why is the effect, or lack of effect, of the soda ash surprising? Assuming the PH was really really low to start with there isn't anything unusual here that I can see.

Also, you need to know your borate level to calculate PH changes with any accuracy.

 

[basjke]

You know, I'm not sure. Never even heard of such a pH buffer, so it may be their own thing.

Just out of curiosity, can you get hold of another pH source for testing? Like a phenol red test or even some good pH strips that measure pH only?

If you mean with pH buffer the Zodiac calibration solution, for sure it is their own thing to make ridiculous money, as they know you don't find it anywhere available and Zodiac charges something like 30$ for 200ml solution. The only other source for testing is 2 different sets of Aquachek 7 in 1 and a basic pool test kit, and they all show a result in the range the meter shows.

After all using the pool calculator tells me that I would need 2235 gram, so it can be correct. I tested the pool again today and it read pH7.3. Now I will have to persuade her that she need to empty the pool for the second time in 6 months, and kick the pool boy as far as she can.

Read the disclaimer in the effects of adding pool chemicals section. You can not use it like you are trying to use it.

I read the disclaimer, but I consider this a large difference in result 0.8pmm against 2.2ppm with the same amount of soda ash

I feel like I am missing something. Why is the effect, or lack of effect, of the soda ash surprising? Assuming the PH was really really low to start with there isn't anything unusual here that I can see.

Also, you need to know your borate level to calculate PH changes with any accuracy.

When I came in the picture the pH was already brought to the 6.5 level, but I needed more or less another 3kg of soda ash to raise it another 0.8ppm. After all it may be correct according to the pool calculator, I'm only confused with the big difference in result depending on how you use the calculator.

Borate will definitely be zero, since for some reason Borax isn't easily available in Thailand. In fact I have looked for it for years and still haven't found it.Same goes for CYA, almost impossible to find in a pool shop in Thailand, and the very select places that have it sell it for 70$ for 4 kg.