Loosing too much chlorine overnight

Just started the BBB method and testing with Taylor K 2006 kit.

Here are the readings:

PH 7.4
FC 9
CC 0
TA 120
CH 320
CYA 100 + by the kit. Pool store says 135.

I'm using 6% bleach and trying to get the chlorine level up based on Ben's Best Guess, 8 to 15.

Yesterday I tested at 9:45 am with FC of 5.5. I added 1.35 gallons of bleach. 12:15 pm tested with FC of 10. 7:20 pm tested with FC 0f 10. Added 1.35 gallons of bleach thinking I would get close to 15. Did not test again last night but tested at 7:40 am with FC of 9.

Should I just keep adding and testing trying my best to hold it at 8 to 15 or should I try shocking up to 25 level?

I live in Central Texas, 100's every day and surface temp of pool is 90 degrees.

Not sure what my next step should be.

Thanks in advance for the help.

In a 15K gallon pool, a 1.35 dose of bleach will add 5.4ppm of chlorine. So, your addition added at 7:20 pm should have taken your cl up to about 15.4ppm. The fact that you lost so much chlorine overnight tells me that you are fighting something in the water. So, yes, you need to shock the pool up to 25 this evening after sundown. Test in the morning within 2 hours of sunup. If you have lost more than 1ppm of cl or if you have a CC reading greater than 0.5ppm, shock it up again. Mid-day tomorrow afternoon, test again if you can and add enough bleach to get back to 25. Do the same tomorrow evening and then try the overnight test again. When you can pass the overnight test, then you can let the cl drift down and keep it between 5-10ppm all the time.

Hope this helps!

Thank you Watermom. I will do this as soon as I return from Austin tomorrow night and post the results.

Regards,

Doug

Thank you, Watermom.

Have to go to Austin today but will begin the shock process tomorrow night and will let you know the results.