Blow off plug keeps blowing off

[Hexmon]

Hi all zeppelin ii z291. Filed fresh water and after noticed that the little black plug keeps blasting off and water shoots out wasting our fresh water whenever we use the pump. Any ideas?

[dwall]

Sounds like the air vent is stopped up. I had dirt dabbers build a nest in mine once.

[hankpage]

The check valve in the city water inlet has failed or has debris in it. Temporary fix .... go to hardware store and get a male hose close nipple and a female hose cap to close off city water inlet. I did this for several months until I could replace the city inlet.

[Steveo57]

You can look into the hose connection and might be able to stick a pointy object in there to dislodge whatever is stuck in the check valve or just get it unstuck.

Here's a video that shows the guts.
https://youtu.be/f1m1Igy8QGc

[Hexmon]

Where is the air vent located?