Help my pool water is possessed!

I have add the recommended start up dose of CYA but it still measures 0. FC will drop from 7 to 0 in 1 day. PH keeps rising also.

No water loss. For past 6 years the PH has not needed any adjusting and CYA has never been an issue since going BBB. Water stays clear but not sparkley.

I live in N TX so the temp has been holding at about 105 for an air temp. I have several trees so even though the pool gets a lot of afternoon sun it is about 40-60% shaded all day. I use Clorox. Added a gal of acid to balance PH then shocked the pool to FC24, held overnight but still no CYA after adding 10lbs and PH is rising again plus using clorox fast.

Thanks

Divetek1

25K fiberglass pool, 1650 Hayward cartridge filter, Intelaflo pump

Welcome

When did you add the CYA and how did you add it to the pool?
Granules or liquid?
What are you using to test your levels?

Thanks for the reply.

I added Granules in a sock floating in the skimmer. I did half a few weeks ago and could not check it for a couple of weeks. I expected it to be low but not 0. I use the test kit from trouble free pools and took a sample to Leslie's for a backup test.

So you did 5 lbs a few weeks ago and then the other 5 lbs half when?

It can take a week to show up on the test and just trying to eliminate that as a reason.

Have you been showing any CCs?

I put the other 5 lbs in last Thursday but I still showed 0 CYA a few weeks after adding the first 5 lbs. I know it was 0 to start with because it was not add after draining and refilling the pool last fall.

I know it confuses me.

Thanks,

Alec

The reason I asked is 5 lbs should raise it by 24ppm which is on the edge of being readable in the test. So if it had been less than a week after the second 5 lbs, there was a chance it might finally register closer to 40ppm.

If not, there may be something in the water breaking the CYA down ... you should catch it and cultivate it and make yourself millions of dollars

Do you have CC showing up that could indicate the presence of ammonia?

Here are my readings for tonight.
PH - 7.8
FC - 0
Alkalinity - 120
CYA - 0

Forgot CC reading shocked the pool to FC - 24

Have not washed filter since adding the 5 lbs of CYA last Thur.

Thanks,

Alec

Did you test after you added the chlorine to see if you go to shock level?