Cloudy water - CH test at 1900!?

[tado921]

I tested it three times in different places in the pool to make sure. Although I do chlorinate with cal-hypo I've never had this problem before (or even remotely close). Sand filter has been running 24X7 for four days, which is usually enough to clear the water. I became suspicious when the water went milky white (light gray?) with no change in two days.

Pool info: 20 X 40 IG vinyl hopper (3 and 8 ft. depths) - 33K gallons

Currrent levels with Taylor K2006:

FC - 11
CC - 0.5
PH - 7.4
TA - 70
CYA - 0
CH - 1900 (!)

Other info: New liner installed last year with refill from hose (yes, it took two days). Fill water tests at CH 200. Everything was fine when closed, and I don't think the cal-hypo used for opening accounts for this level in the pool. I'm going to do the lime softening bucket test to see if that will help.

Any ideas what could raise the CH up so high?

I follow BBB so no other gunk has been added, although I may have made things worse by adding baking soda to get the TA/pH up. Thanks in advance!

Tad

[tado921]

Nobody huh? Ok, I will be the guinea pig. :)

Bucket test results: Following the instructions in the sticky post I added 1Tsp bleach and 20 Tsp soda ash to 4 gallons of pool water (CH 1900 = 19 Tsp + 1 extra). After 24 hours the water was still a bit cloudy but better, CH tested at around 400. After 48 hours the water was perfectly clear and I could see the calcium buildup on the bottom of the bucket. CH tested at 200 (!).

Concerns: When adding the soda ash to the bucket there was an initial buildup of a crust on the bottom of the bucket that dissolved after a few minutes of stirring. I think it was the soda ash clumping together, and I worry a bit that it might clog the filter if I add through the skimmer.

If I add the soda ash through the skimmer it will be concentrated in the filter for a short time, and I worry that it will cause localized scaling inside it. For these reasons I'm going to dump directly into the pool and brush to stir it up.

I'm still wondering how the CH got that high. I called a friend who runs a pool company and he has never heard of this, even when using cal hypo. There must be some source for it, but we can't figure out what it is. He also doesn't believe me and is coming by today to check it himself. :)

I told him about the soda ash treatment and he has never heard of it. I told him to come here and read up on it, and I will show him the bucket test. More to come...

[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.