i found a check valve that dosent have a tight fit( lets the pressure out if theirs too much, i hope). tower sells 2 kinds one for glow and one for gas, the one for gas it says its not as solid as the glow and will let the pressure back out, how well it works i dont know but its worth a shot. i just dont want to canabalize another tank. but i think the in tank filter is the cause. when i removed it the brass pipe went all the way to the bottom of the filter and when i lifted it about 1/8 inch you could blow through it with no restrictions. i think cen should rethink the in tank filter and not use it and let the purchaser decide on an inline filter to use.