water valve purpose?

Ok fellas, on my 1975 Slant six Scamp, I removed all the AC system parts under the hood but.....
There is a "water valve" mounted on the right inner fender which the 1/2" heater hose runs to and another 1/2" hose on the other end goes to the heater core. Do I still need this valve? Can I just use a new hose and remove the water valve and run the hose directly from the water pump to the heater core?

My buddy said the car will continually have water running to the heater core. I thought it runs to the core when the temp selector is moved to "heat" inside the car. Help.