Welcome to our forum.
I pretty much use the same protocol.......1-2 tsp dichlor after each use, and generally MPS to shock with an occasional dichlor shock if I can handle not using the tub for a few days. Canada.....I'm a little puzzled.....you said "shock with MPS and about once every two weeks shock dose of dichlor." How often are you shocking with MPS if you are also shocking every other week with dichlor? I only shock the tub, whether it be dichlor or MPS, a max of every other week.
My Arctic information says to shock with BOTH MPS and Dichlor (per my spa size, I am told to use 1oz of Dichlor and 2oz of MPS). All I read in this forum talks about using either / or, but not both at the same time. What do you all think? Also, one document I have from them states to add them both at the same time, but the other says to add the MPS, let it run for 30 mins and then add the Dichlor and let it run again. Is this a better idea than adding both at the same time?
As someone mentioned, there are enhanced shock products that contain both, so applying together is no problem.I once read an argument for applying MPS first. The theory was that chlorine is a stronger oxidizer, so if applied together, the chlorine would get used up oxidizing organics, rather than sanitizing, while the MPS would be left with nothing to do until more organics are introduced. According to that paper, if you put the MPS in first, it will do the oxidizing, leaving the chlorine free to sanitize.
That makes a lot of sense. I wonder if you have to wait a period of time for the MPS to complete oxidizing.