Very low and unresponsive ph

[Pieter]

Hi guys and girls,
Need advise please. We have a 106,000 gallon pool. The ph is reading 6.8 or lower as that is as low as my tester goes. So I slowly started to add soda ash. Well I stopped after 3 days on 44 pounds of soda ash with absolutely no difference besides my pool having a green color but not the same type of algae green. Thinking it might be metals I shocked the pool with chlorine to help with the oxidation of the metals but no luck there. Resources like taking water for testing is non existent here. My pump is running 24/7. My TA is about 70.
open for suggestions.

 

[JamesW]

What's the cya?

I suspect that the cya is very high. Probably 200+.

Do you use trichlor tabs?

If yes, how many pounds total have been used since the pool was filled?

 

[Pieter]

My CYO is actually zero and because of my already low ph i am not sure what to do. No i use normal chlorine with a stabilizer. all that is available here. This pool is 30 years old and i have been keeping an eye over it for only a month now. The water was always clear but with low ph > 6.8. After adding the soda ash my ph is still the same but overnight being surprised with green water. I am not sure if metals are causing it.

 

[domct203]

My CYO is actually zero and because of my already low ph i am not sure what to do. No i use normal chlorine with a stabilizer. all that is available here. This pool is 30 years old and i have been keeping an eye over it for only a month now. The water was always clear but with low ph > 6.8. After adding the soda ash my ph is still the same but overnight being surprised with green water. I am not sure if metals are causing it.

What is your 'normal chlorine'? The most popular form of solid chlorine on the planet is trichlor/dichlor, both of which add CYA (stabilizer).

What is your FC level? CC level?

Why do you think your CYA is zero, has it been tested?

 

[Pieter]

We use Trichlor. Test strip show that my CYA is zero. My FC is 3 and my TCI is 3 inching towards 4

 

[jblizzle]

Trichlor adds CYA, so no way yours is 0. Which is why we do not recommend using test strips. It is also acidic which is why your pH is low.

 

[mknauss]

I am assuming Abuja is in Nigeria? Have you checked on being able to have Taylor testing chemicals imported? Or if someone coming from the USA can bring them?

 

[JamesW]

How many pounds of trichlor have been used since the pool was filled?

Do you have a heater or copper pipes?

Total alkalinity reduces ph drop from introduced acid.

Total acidity reduces ph rise from introduced bases.

Most likely, high levels of cyanuric acid are creating high total acidity and reducing ph rise from the base you're using.

Most of the Total alkalinity in the water is probably from cyanurate.

The added carbonate has probably all been converted into carbonic acid and then carbon dioxide and water. The carbon dioxide offgasses leaving little carbonate.

Once the carbonate alkalinity hits 80 to 100, the ph usually gets to at least 7.2.

If your test kit has base demand, that can help.

 

[Pieter]

Thanks, should I then use bleach?

 

[JamesW]

You need to figure out what the cyanuric acid level is and make sure that it's in the correct range.

Then use sodium hypochlorite to maintain the chlorine at about 7.5% to 10% of cya.

 

[Pieter]

Pool is 30 years old, only been here a month and I doubt it was filled in the near history. I have been using an average of 4,5 pounds daily and the pool is 106,000 gallons

 

[Pieter]

No only from the U.K. And I am from South Africa. Chlorine will fall under hazmat provisions so only by sea freight

 

[jblizzle]

That amount of Trichlor would add 4.7ppm of FC (which is high for a daily requirement) and 2.8ppm of CYA, and lower the pH by 0.2.

So in 30 days, you would have added 84ppm of CYA from using Trichlor at that rate.

 

[Pieter]

Ok, that is doing the opposite of what I am trying. My access to various chemicals are very limited. Should be able to get bleach. Would that be a better alternative?

 

[jblizzle]

Yes, bleach only add chlorine and some salt, which is fine. But you have to know the CYA and get it under control to know what FC level you need to maintain. None of this is really easy to do with test strips.

 

[jblizzle]

You can do the calculations yourself using PoolMath, link at top and in my signature.

 

[JamesW]

135 lbs trichlor added to 106,000 gallons would lower the TA by about 98 ppm.

The cyanuric acid added in the last 30 days was added to whatever cyanuric acid that was already in the water.

If the pool has been operated on tabs for a while, the CYA is probably super high.

You might be better off doing a drain and refill.

However, you should not drain without getting a knowledgeable person to certify that draining is safe.

Draining the pool could potentially cause the pool to pop out of the ground or otherwise be damaged.

How deep is the pool?

What's the groundwater situation?

 

[Pieter]

Draining the pool will be the last option. In the meantime I managed to connect with the state water board. They are testing a sample of the borehole water and the pool. Unfortunately they cannot test CyA. I have also learned that the water here is very high in manganese.