Ben,
Thank you for your reply.
Before I read your reply, I back washed cleaned hayward filter. Then added DE (3 lbs) to the skimmer. I let pump run about 1 hour, checked with strips - still no calorie. So I added 1 bag (1lb) of multi-shock. I tested the water about 20 minutes later. you guessed it- STILL NO CHLORINE according to strips.

I will try your suggestion today or tomorrow.

Sue