That may be true with a bottom feed tank but not sure with a TF style pick up tube. If you have done that, I yield. There seems to be no way it can be blocked with all new system unless a rubber hose is kinked. The flow test needs to be done ASAP and I would like to know how the truck runs. This truck may have a vented cap issue. He says he "clears" it by back blowing. That means an obstruction is going out into the sock, then back in? I don't buy that. Also you can blow the sock off that way.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn