No FC but pool is crystal clear

[PoolDoc]

Losing chlorine overnight actually means you are accomplishing something: breaking down whatever residue is present in your pool. (Daytime loss is often just to sunlight.)

[soupy01833]

well, this is the first morning I had both FC and TAC when I woke up. It was not much but at least it was around FC=3 and TAC=3. It is mostly gone now during the day. Do I need to keep going to shock level? or simply try to get it to stay at around 6-7?

My 2006 kit should be here this week sometime. Strips are all I have to measure FC at the moment.

[PoolDoc]

You probably need to use dichlor long enough to get your stabilizer up. Dichlor adds 9 ppm of stabilizer for every 10 ppm of chlorine. I'll post the info below:

Undiluted dichlor is getting hard to find, but is available at Sams Club and via Amazon. It's sometimes available at Lowes or Home Depot, but you'll need to be a expert label-reader to recognize it!

PoolBrand granular dichlor 50lbs @ Sams Club => ~$2.20/lb (May 2014 in Chattanooga)
PoolBrand dichlor bagged shock 24lbs @ Sams Club => ~$2.50/lb (May 2014 in Chattanooga)

Kem-Tek dichlor 22 lbs @ Amazon => ~$3.50/lb (May 2014)
Kem-Tek dichlor 12 lbs @ Amazon => ~$4.10/lb (May 2014)
Kem-Tek dichlor 5 lbs @ Amazon => ~$5.00/lb (May 2014)
Kem-Tek dichlor 2 lbs @ Amazon => ~$9.00/lb (May 2014)

Keep in mind that Amazon products normally ship free; and that in many parts of the country, you will not have to pay sales tax. Shipping + tax can increase the cost from other suppliers by 15 - 40%, so compare delivered cost, not nominal price.

[soupy01833]

If my CYA is 40 how much higher do I want it?

[Watermom]

Most pools do well with CYA around 50ppm.