Welcome to our forum.
I know I am all over the forum with these chem questions, but forgive me. the more I try to undestand what others are doing, the more I get confused....Tony, This sounds backwards. You put Shock into the tub BEFORE you use it, and once a week add dichlor? I thought you used Dichlor AFTER each use and shocked with MPS once a week.?
What is Dichlor and MPS ?
My preference is to shock with MPS over chlorine. I believe it is a better oxidizer and I don't have to put my spa out of commission to wait for the chlorine level to come down to use it.I tend to use a minimal amount of dichlor after each use, so I like to be sure I raise my free chlorine level to 3-5 ppm once per week.