Erratic CYA levels in salt water pool

[DLM]

Hi I am new to taking care of our salt water pool and can not stabilize the cya level. When converting to salt water last season the pool company did not put any cya in and we had algae all summer. This season started off again with high phosphate levels, zero chlorine and algae.After finding this great site I learned about cya and salt water pools. Pool size is 42500 gallons, plaster . I put in 20 lbs of cya last month and reached 45 ppm. After two heat waves pool was cloudy and water tested 26 ppm. I did not drain any water from pool.
Put in 10 lbs last week and went to 28 ppm. Pool store said pool was haunted! I would really appreciate any insights
We are in New York

 

[Isaac-1]

This sounds like you are making the mistake of trusting pool store testing as being accurate

 

[jblizzle]

Welcome to TFP!!!

I agree with Isaac, your mistake is trusting the pool store ... especially when the CYA test is the one they are the worst at.

Get one of the Recommended Test Kits and start to understand your water.

 

[Charlie_R]

i'll add in something too --

READ POOL SCHOOL!

Richard, where is that cool graphic you have? and why didn't you use it?

 

[Patrick_B]

Welcome to the forum and kudos to you for checking out the info in Pool School.

It would be exceedingly rare for your CYA to drop that much. So much so that I would strongly agree this is test error. I'll bet your CYA is pretty good and you simply have not had adequate and consistent chlorination. You've already heard our theory here on education and testing on your own I am sure, so I will just chime in as well on getting a good kit. When you do, you will have control and understanding, along with a clear, safe, and sparkling pool.

 

[DLM]

What would cause inadequate chlorination in SWG set at super chlorinate? We did have two heat waves and pool temp reached 88 degrees. Water became cloudy and chlorine started dropping. Had water tested at Leslie's on 7/10: FC .75 TC 1 salt 3400 Calcium 140 CYA 26 alkalinity 80 PH 7.8 Added @ 12 lbs of cya mostly through broadcast method and had water tested again on 7/16: FC 2 TC 2 salt 3200 Calcium 140 cya 28 alkalinity 90 PH 7.8
They tested cya twice and use the same test kit as recommended in pool school. Really appreciate any and all help.

 

[jblizzle]

But they use the wrong lighting for the CYA test which affects the result.

Chlorine is consumed by the sun and organics in the water. With the low CYA, you were losing a lot to the sun, but at this point there is probably stuff growing as well. The SWG well not add the FC fast enough and you should be supplementing with bleach.

Likely you need the SLAM process to clear the pool.