CYA level

[dtrebus]

I put 1 lb of dry CYA doing the sock method 2 days ago. Calculated to raise CYA from 30 to 40.
I noticed yesterday, my pH was 7.2 (had been steady 7.8). Today, my pH was back to 7.8, but CYA still at 30.
I test at the same location and roughly same time each day. What can be happening?

 

[Texas Splash]

According to my PoolMath estimate for your 17K pool, 1 lb of stabilizer should increase the CYA by about 7 ppm. Add to that the variance for CYA testing which can be a little tricky, and you may be close. The changing pH would have minimal impact on pH (about 0.13 worth).

Are your weather conditions consistent for the CYA test? Outside on a clear, sunny day, etc?

 

[dtrebus]

Actually I put in a little more than one pound, and 2 days later, same level. The test was on a clear sunny day. Followed guidance with my back to sun and everything. Weird how a couple weeks ago CYA was 40 now it's 30. MAybe it was from siphoning off 2-3 inches of water?

 

[Texas Splash]

MAybe it was from siphoning off 2-3 inches of water?

Losing water certainly can effect the CYA.

 

[dtrebus]

So my CYA is less than 30 now. tube all the way filled and can still see black dot. was gone most of yesterday so didnt test, but FC is down.
pH 7.8
FC 0.5
CC 0.5
CYA <30
TA 90
Should I add CYA first or FC, or does it matter?

 

[dtrebus]

I'm at a loss....
pH 7.8
FC 5
CC 0
CYA <30

Yesterday I added a little over 2lbs CYA (per poolmath) and CYA still less that 30. I don't stare at the dot, just put some liquid in and glance, but tube is all the way filled and can still see black dot. Added over 4lbs of CYA in the past 5 days and it went down???

 

[mknauss]

Be sure to wait 24-48 hours after all the CYA is dissolved from the sock before you test.

If you added the CYA, it is in the water. Unless you have had large amounts of overflow due to rain.

 

[dtrebus]

It rained some last night and this morning, but it was sunday when I removed about 2-3 inches of water above the skimmer. How come the first dose of CYA (calculated to raise it from 30 to 40) didn't show anything, and over the next couple of days, it went to tube being filled all the way and still seeing the dot? I will wait until Sunday to check again.. just don't want to have it swing to too much CYA

 

[WWells]

I seem to struggle with CYA, opened pool 3 weeks ago and added stabilizer to get to 50ppm, test showing 30-40, pool is clear and otherwise numbers look good, we have had a lot of rain lately.

FC 2.5, CC 0, TC 2.5
PH 7.8
TA 90
CH 30 - never have a straight answer if I need to have a high CH with a fiberglass pool with no tile
Salt 3050
Temp 77

Should add more to get to 70-80?