HPA question

[avantpaintballer99]

ok so ive noticed that my hpa tank is losing air after a while
like after i fill it about two/three hours later its already lost about 500 lbs
then after about 5 days later it usaly goes all the way down to about 2000 and stays there. and the tank is always in my house, so theres no extreme tempurature differences.
this cant be normal can it? should i just reseal it with teflon or use silicon?
by the way the tank is 4500/68

thanks