Excellent info Louis! I pray I never have that problem. It will be rough getting at all the parts.
I think the reason for a knife valve is so there are 2 controls, lest one be faulty. 1. the hose type bib used for back flushing and, 2. the knife valve. (Why not a ball valve?)
I have many talents, but mechanical skills is not one of them! My wife is far more logical when it comes to mechanics!.
Thanks