Cloudy water - CH test at 1900!?

[tado921]

OK, so I was multiplying the drops by 100 instead of 10, so my CH is actually at 190. Glad I caught it before I bought all the stuff. However, I have a question:

In the water softening procedure it says to add 9 pounds of soda ash for every tablespoon in the bucket test, plus one more. Basically it is calling for a ratio of added soda ash depending on the CH level. However, it seems to me that the actual method is to get the pH above 10 in order to get calcium to precipitate. It wouldn't actually matter what the CH level is, I just need to get pH to 10. Is this not correct?

For example, what if the CH is at 400 and I want to lower it. According to the procedure I would be adding about 45 pounds of soda ash. If my starting pH is on the low end, I may only get to 9 or 9.5. Am I off base on this?

[PoolDoc]

In the water softening procedure it says to add 9 pounds of soda ash for every tablespoon in the bucket test, plus one more. Basically it is calling for a ratio of added soda ash depending on the CH level. However, it seems to me that the actual method is to get the pH above 10 in order to get calcium to precipitate. It wouldn't actually matter what the CH level is, I just need to get pH to 10. Is this not correct?

Partially. Without a meter, most people can't test for pH = 10, so providing instruction based on that is useless.

But, also, the chemistry of the precipitation requires an excess of carbonate ions (=CO4) in order to capture all the calcium. The amount of soda ash needed is determined by the quantity of calcium present.

It's very, very surprising that you'd add soda ash, drop calcium to the bottom, and still end up with the original 200 ppm. I'm not sure what actually is going on with your water.

[tado921]

Thanks for the explanation, I appreciate it.

It turns out my filter sand was too low, measuring 16 inches from the top of the tank. I added two bags of sand to bring it up to 12 inches. Now the water is beginning to clear as expected, and I should be good in another day or so. I guess over time it had slowly washed out with backwashing and such and finally got to the point where it wasn't working very well.

As for the strange results from my bucket test, I made a typo. The final result was 20ppm, not 200.

[PoolDoc]

As for the strange results from my bucket test, I made a typo. The final result was 20ppm, not 200.

OK, I feel better. That's what I'd expect.