How I descale my Blazer.
Poor decaling agent into header tank, start engine, press trigger on wand, wait till you see agent coming through, turn off engine leave for ½ hour, restart engine and do the same again. Then I vac out header tank and let it fill will clean water, remover bypass strainer and orifice re start engine (make sure no one or thing is in the way) to flush out turn off when happy, clean strainer if needed and check orifice for the hole, refit them! Remove wand filter restart engine and flush out solution hose and wand, clean wand filters if needed, refit them, restart engine to check for spray Patten.
Chemical metering system is in the off position if only using MS.
The same above applies if using the Chemical metering system but a small bucket with descaler is needed.
I have always used soft water from my home but have sometime used customers and on big jobs direct feed to no ill effects.
What I have found grit can be a big problem if it blocks the orifice.

Len