Linear piston pump

[Chee]

I just received my pump today and I’m having trouble with what I’m experiencing so any help would be appreciated. 
 

I bought this pump to use as an airlift for my soon to build pond. After receiving it I attached a regular clear hose to it and stuck the end into a 55 gallon barrel full of water. To my surprise the bubbles stopped pushing out after 1-2 inch of the hose is in the water. It will push out air until I drop the hose a few inches from the surface. 
 

Is my unit not working right? Even on the 1 page manual it shows the pump being used in a pond setting below the water surface so I’m kind of confused. Again any help would be appreciated. I also for some reason can not reach the coop team through their site at the moment so decided to post here

[Andy's Fish Den]

I may be wrong, but I believe the pumps are more for volume of air, not pressure. If you are using a larger clear hose, it wouldn't be able to build the pressure required to overcome the water pressure. try capping the end and drilling a couple of holes in the hose. 

[Chee]

Thank you for the reply. The hose I was using was either a 3/4-1” hose and I did also try it with my thumb closing off portions of the opening with the same results.  
 

For anyone who has one, is this black boot from the inside suppose to look like this? Unattached to the outlet.

Edited March 5, 2021 by Chee

[StevesFishTanks]

I think you need a smaller hose. That picture is interesting but there is a gasket so it looks like it pressurizes the entire chamber and acts as a buffer. 

[Chee]

Yeah that space was definitely suspicious and it turned up to be the problem. I also thought it was suppose to be that way because of that gasket too but Cory just made a video on how that was suppose to be connected.