new piston pump, air in hose

Hi yesterday we bought a pompco piston pump. Pump works well but there is air in the hose. And so recharging the water tank to 50psi takes about 15 min. The pump has been primed. It is bubbling where the water discharges from the well. I am worried something happened to the underground well l i ne that is allowing air in. When we finally got some water to come through it was rusty and still seems slightly discoloured. We have drained the lines to the house several times. We havent had any trouble with freezing lines or running low on water and it has been wet here lately. We heat our house with water and it is below 0 C now so critical we get water soon. It has already been 2 days.
Any ideas are appreciated
Thanks