Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Leaking, rotted outlet pipe

I could see that technique working within a vertical hollow structure. But, in a horizontal pipe, gravity would pull the sealant to the bottom of the cylinder - which would then push the air bladder to the top of the cylinder. Not necessarily a bad effect in this particular case. However, a support-membrane would be needed to prevent the sealant from draining through the exit-pipe's perforations.