Don't put it in your freshwater tank, just drain it and use a
bypass kit. Its extremely easy to put in if you can access it. I was actually afraid to install one in mine at first, but I said why not and it was so simple. All connections only require hand tight.
You want to put the bypass kit between your freshwater tank and the pump.
Here is my install.
Before, Hose from freshwater tank to the Left side (input) of pump.
After, Hose from freshwater goes to T and T goes to inlet of pump. You can see the clear fill hose just sits there (left side of pic) until I'm ready to use it.
You may notice an additional hose (white w/ red label) for ease of connection. That came from the HW store. Its a bathroom sink/toilet hose. 1/2" I believe... Someone this site gave me that tip and it worked great!
Don't forget the outdoor shower if you have one.
You can use a
handpump to do your city inlet. Don't forget to open a faucet while your pumping it through.
Do you have a bypass setup for your hotwater tank? You can see the 3 valves on my HW tank. You should install that as well so you don't fill your HW tank up with antifreeze.
(Others prefer the blowing the lines out with air method)