I am ready to redo the plumbing from my pump to the rest of the house. My issue is the pressure tank does not have a separate isolation valve. So, my plan is to drain it down and clean it out. However, I am concerned that the pump will loose it's prime. I am also concerned with the sludge from the bottom contaminating the system. If I isolate the system, and shut the pump off, can the tank be drained without loosing suction and without contaminating the system? I will be changing out all the lines.