I just replaced my water tank to a blader tank , and replaced my check valve to . When the pump turns on I get air pushed into my water lines what would cause this ?

You initially had an older system. It worked by allowing the wellpipe to drain every time the pump shuts off. There is a small air admittance valve located on, or very near, the wellpipe. It allows air to enter the wellpipe every time the pump cuts off. That air would then be pumped into your old pressure tank every time the pump cut back on to keep it charged with air. That is not needed with a bladder tank. You need to plug that air valve.

Yes this is correct I had a copper line running from the pump to the tank about half way up. I took this out and pluged the hole at the pump with a plug is this the one you are talking about ? I also re piped the whole system from the well pipe to the pump and so on. It is like if the system sets for about 5 hours it drains for some reason and whe we us it and the pump comes on then this is when we get the air.if we are using off and on washing dishies , cloths so on it does not seam to do it. Its like it drains from the pump to the well it self .